Homo Floresiensis Timeline

Homo Floresiensis Timeline

  • c. 2600000 BCE - c. 12000 BCE

    The Palaeolithic (or Old Stone Age) period, ranging from c. 2,6 million years ago until c. 12,000 years ago.

  • c. 12000 BCE

    The Pleistocene epoch, ranging from c. 12,000 years ago. It is characterised by repeated cycles of glacials and interglacials.

  • c. 100000 BCE - c. 60000 BCE

    Recently determined age of the Homo floresiensis specimens.


The origin of our species

Our Human Evolution gallery explores the origins of Homo sapiens, tracing our lineage since it split from that of our closest living relatives, the chimpanzee and the bonobo.

Gallery developer Jenny Wong tells us more.

The gallery takes visitors on an epic journey spanning the last seven million years.

Starting in Africa with our early hominin relatives (who are more closely related to us than to chimpanzees), visitors will travel forward in time to meet our ancient human relatives as they spread into Europe and Asia. The journey ends with modern humans as the only surviving human species in the world today.

Along the way, visitors can see star specimens from the Museum collections, and get to grips with some of the latest research shedding light on our past.

Conservator Effie Verveniotou and human origins researcher Dr Louise Humphrey examine the oldest nearly complete modern human skeleton ever found in Britain before it goes on display in the gallery. Cheddar Man lived around 10,000 years ago.


ANU has a huge variety of support services, programs and activities to enhance your student experience.

We can be 99 per cent sure it's not related to Homo erectus and nearly 100 per cent chance it isn't a malformed Homo sapiens.

The most comprehensive study on the bones of Homo floresiensis, a species of tiny human discovered on the Indonesian island of Flores in 2003, has found that they most likely evolved from an ancestor in Africa and not from Homo erectus as has been widely believed.

The study by The Australian National University (ANU) found Homo floresiensis, dubbed "the hobbits" due to their small stature, were most likely a sister species of Homo habilis - one of the earliest known species of human found in Africa 1.75 million years ago.

Data from the study concluded there was no evidence for the popular theory that Homo floresiensis evolved from the much larger Homo erectus, the only other early hominid known to have lived in the region with fossils discovered on the Indonesian mainland of Java.

Study leader Dr Debbie Argue of the ANU School of Archaeology & Anthropology, said the results should help put to rest a debate that has been hotly contested ever since Homo floresiensis was discovered.

"The analyses show that on the family tree, Homo floresiensis was likely a sister species of Homo habilis. It means these two shared a common ancestor," Dr Argue said.

"It's possible that Homo floresiensis evolved in Africa and migrated, or the common ancestor moved from Africa then evolved into Homo floresiensis somewhere."

Homo floresiensis is known to have lived on Flores until as recently as 54,000 years ago.

The study was the result of an Australian Research Council grant in 2010 that enabled the researchers to explore where the newly-found species fits in the human evolutionary tree.

Where previous research had focused mostly on the skull and lower jaw, this study used 133 data points ranging across the skull, jaws, teeth, arms, legs and shoulders.

Dr Argue said none of the data supported the theory that Homo floresiensis evolved from Homo erectus.

"We looked at whether Homo floresiensis could be descended from Homo erectus," she said.

"We found that if you try and link them on the family tree, you get a very unsupported result. All the tests say it doesn't fit - it's just not a viable theory."

Dr Argue said this was supported by the fact that in many features, such as the structure of the jaw, Homo floresiensis was more primitive than Homo erectus.

"Logically, it would be hard to understand how you could have that regression - why would the jaw of Homo erectus evolve back to the primitive condition we see in Homo floresiensis?"

Dr Argue said the analyses could also support the theory that Homo floresiensis could have branched off earlier in the timeline, more than 1.75 million years ago.

"If this was the case Homo floresiensis would have evolved before the earliest Homo habilis, which would make it very archaic indeed," she said.

Professor Mike Lee of Flinders University and the South Australian Museum, used statistical modeling to analyse the data.

"When we did the analysis there was really clear support for the relationship with Homo habilis. Homo floresiensis occupied a very primitive position on the human evolutionary tree," Professor Lee said.

"We can be 99 per cent sure it's not related to Homo erectus and nearly 100 per cent chance it isn't a malformed Homo sapiens," Professor Lee said.

Dr Argue undertook the study along with ANU Professor Colin Groves, and Professor William Jungers from Stony Brook University, USA. The findings have been released in the Journal of Human Evolution.


Homo Floresiensis:The Hobbit of Human Ancestry

Homo floresiensis has been dubbed "hobbit" for its dimunitive size. Its existence until 17,000 years ago was surprising enough, but its probable ancestry is raising spellbinding questions.

Fossil Specimens Available

The original find was a cavewoman, about 3 feet tall, on the island of Flores in Indonesia. LB1 had an almost complete skull, and a partial skeleton that included leg bones, parts of the pelvis, feet, hands, and some other fragments.

Original cavewoman skull
by Ryan Somma

A number of other specimens of Homo floresiensis have been found since, dating from 38,000 to 17,000 years ago, when they are believed to have went extinct.

Floresiensis is a well-established species of hominid. However, it has a small brain, even for its size. Its skull is very human-looking, but it has other traits that have raised some intriguing speculation.

Where Did Homo Floresiensis Come From?

There are many issues. Here are the primary ones:

  • Stone tools probably made by the hobbits have been found dating back 1.1 million years. There are even current claims that date will be pushed back to 2 million years.
  • If Homo floresiensis descended from Homo erectus, as first assumed, then there was an unexplainable decrease in brain size, even relative to body mass.
  • The Flores hobbits have several anatomical similarities to Homo habilis, a species which never left Africa.
  • Brain size suggests they could have descended from Homo georgicus, an intermediate between habilis and erectus that was found in eastern Europe, but they bear more similarity to Homo habilis.
  • If their tools go back to 2 million years ago, then the Homo floresiensis predates Homo georgicus.

Relationship to Homo habilis

Homo floresiensis bears a lot of resemblance to both Australopithecus afarensisਊnd Homo habilis.

In particular, their feet are large, 70% of their femur as compared to 55% in modern humans their wrist bones have a trapezoidal shape that would have made tool-making more difficult for them and, of course, they had small brains.

A recent study looked at both absolute and relative brain size in primate lineages using 37 current species and 23 fossil species. They concluded that a decrease in relative brain size over time is rare but does happen.

If Homo floresiensis descended from Homo erectus, though, then the decrease in relative brain size is dramatic and unparalleled in primate evolution.

Thus, the thought is that these hobbits descended from Homo habilis, which was already small in stature, and the decrease in brain size is almost non-existent, much more in line with what we see as possible in other primate lineages.

The Problem of Travel

The problem is that if Homo floresiensis descended from Homo habilis, then how did they get to Indonesia? Homo habilis is a purely African species, found only in the Great Rift Valley.

One article I consulted suggests that as difficult as it is to believe that floresiensis left Africa and traveled to Indonesia, that is what must have happened.

I can't buy it. My love of learning is primarily historical, and you just don't invent historical events for which there is no evidence.

I vote for Homo georgicus or a yet unknown species as the progenitor of our tiny Flores cavewoman. Homo georgicus is intermediate between habilis and erectus, and georgicus fossils were unearthed at Dminisi, Georgia, in Eastern Europe. Now you've got a species that has already left Africa, and the decrease in relative brain size is still within norms for primate evolution.

The decrease in body size would be accounted for by the fact that dwarfism is typical on islands, and the decrease in relative brain size would be a product of a million years on an island or islands in Indonesia without competition from other hominids. Brains require a lot of energy, so if they're not needed for survival, the decrease would be expected.

What Became of Homo Floresiensis?

There are two possibilities.

Articles Consulted

One, there was an eruption in Indonesia around 17,000 years ago. Volcanic ash was found in the ground above the cavewoman find. Perhaps an eruption either suffocated the hobbits in ash or destroyed the island so they starved.

The other possibility is that Homo sapiens showed up. We have a history of extinctionਏollowing and surrounding us. Mammoths and Neandertal men would be examples. It's entirely possible humans showed up and used up their resources or took enough of their land that they could no longer survive.

In our defense, there are still pygmy elephants, rats, and komodo dragons on Flores, which is what Homo floresiensis hunted. Thus, there is evidence against our driving them to extinction.

Final Interesting Note

Mike Morwood, the original discoverer, has reported that he has found stone tools at other sites that are up to 2 million years old.

If that turns out to be true, then unless we find other hominin on the islands, Homo floresiensis certainly predates Homo erectus and possibly georgicus as well. Wouldn't it be amazing if it is in Indonesia that we find the first evidence for human ancestors outside of Africa!


Human Origins

16,500,000 years ago, Africa became arider as fluctuations in the climate caused a majority of the woodland environments to be replaced by open savannas. As a result, the ancestors of the Hominidae family, the greater apes, underwent speciation from the Hylobatidae family, the lesser apes, as the Hominoidea superfamily separated out into different species of hominids and gibbons.

16,000,000 years ago, hominids were beginn i ng to use more and more elaborate systems of communication, although complex language did not yet exist. As time went on, they produced an array of sounds through the use of vocal organs as well as by way of chest-thumping, ground-slapping, and tree-drumming. Facial expressions, like teeth-baring, along with body postures also played an important role in this.

15,000,000 years ago, drier, more seasonal woodlands spread in eastern Africa so the distribution of fruits became less spatially and temporally abundant. As a consequence of this, leaves became the common dietary staple of the hominid populations that lived a million generations ago.

14,000,000 years ago, more and more primates in the Hominidae family began to leave the treetops and live on the ground, and they exhibited a greater range of sizes than that of modern apes. However, less hospitable cooler conditions in the Northern Hemisphere eventually caused many species to die out, although some hominids survived by migrating south.

13,500,000 years ago, Hominidae populations migrated to Southern Asia where the hominines eventually speciated from the ancestors of the orangutan. The Homininae comprised all of the extinct and extant species that arose after the split from Ponginae.

12,000,000 years ago, the diversity of hominids and hominines declined as the tropical and subtropical habitats of Europe and Asia began to contract and become concentrated closer to the equator as a result of tectonic forces.

10,500,000 years ago, as the hominines gave rise to hominins the descendants of the early apes diverged into two lineages, the gorillas and the line that would lead to humans and chimpanzees. Then, when the East African Rift Valley formed, life evolved separately on each side.

9,500,000 years ago, life was much harder for the hominids, hominines, and hominins that clung to the remaining trees of the open savanna. Eventually, the apes adapted to living in a range of habitats, including forests, open-canopy woodlands, and savannas.

8,000,000 years ago, it became increasingly difficult for hominids, hominines, and hominins to survive through arboreal means. Hominoids became extinct in Europe and their populations and distribution were significantly reduced in Asia because climatic disruptions in the middle latitudes made these habitats unsuitable.

6,000,000 years ago, Orrorin tugenensis was an early species of Homininae, having descended from Sahelanthropus tchadensis. In time, these hominines adapted through hundreds of generations of physiological changes, as their front legs became useful as arms with which to forage.

5,700,000 years ago, hominans speciated from the ancestors of chimpanzees when a telomere-telomere fusion of ancestral ape chromosomes gave rise to a specific mutation in our lineage. Then, scattered clans of evolving apes were forced to endure the harsh conditions of the savanna.

5,600,000 years ago, Ardipithecus kadabba lived in and around Ethiopia, with a body and brain size similar to that of extant chimpanzees. The Miocene hominans were bipedal apes that had canines resembling those found in later species but that still projected beyond the tooth row, reflective of inherent aggression.

4,800,000 years ago, a reduction of the canines in certain ape species related to an increase in social cooperation and an accompanying decrease in the need for males to make aggressive displays.

4,600,000 years ago, the nervous systems of select apes were becoming reorganized to operate in more coordinated ways. This triggered what would become a crucial growth of the brain, which enabled the ancient apes to use hunks of rock and wood to crack open nuts or dig for tubers, although they didn’t shape these tools in any systematic way.

4,400,000 years ago, as a Plesticene hominan, Ardipithecus ramidus had a relatively small brain, measuring about 325 cm³. The species was arboreal but capable of bipedal locomotion as evidenced by its bowl-shaped pelvis, the angle of its foramen magnum, and its thinner wrist bones. Although its feet were still adapted for grasping rather than walking for long distances.

4,200,000 years ago, the Australopithecus genus appeared. Australopithecus anamensis lived in northeastern Africa as the predecessor of Australopithecus afarensis. They displayed a high degree of sexual dimorphism with males being about 50% larger than females.

3,900,000 years ago, Australopithecus afarensis had reduced canines and molars. A. afarensis also had a relatively small brain size of 400 cm³ and a prognathic face. They stood about 1.2 meters tall and likely increased their diet to include meat from scavenging opportunities.

3,600,000 years ago, australopithecines had shorter and less divergent toes. So, their arched feet worked as rigid levers for pushing off the ground during each step. Their spines had an S-shaped curve, which shortened the overall length of their torsos and gave them rigidity and balance when standing.

3,350,000 years ago, australopithecines exhibited a more human-like cranium which permitted a larger brain compared to their body size, along with more human-like facial features. Their brain was only slightly less than half of ours. With no sharp teeth or claws, this species had to use group displays as a scare tactic.

3,150,000 years ago, australopithecines began to explore new territory. Once they found a place they liked, australopithecines would take control of a large area. As a result, troops often engaged in fierce territorial disputes. So, in addition to being at the mercy of predators, australopithecines were also constantly on guard against their rivals.

2,900,000 years ago, the Paranthropus genus emerged, being morphologically distinct from Australopithecus, having highly specialized features based on their regionally limited diet. As incredibly robust hominans, the members of this group represented a unique development within the overall hominid family.

2,580,000 years ago, Australopithecus africanus was slender and significantly more like modern humans than Au. afarensis, with a more human-like cranium permitting a larger brain and more humanoid facial features. They had a brain capacity of about 450 cm³. Au. africanus females even underwent an evolutionary adaptation to better bear lumbar load during pregnancy.

2,450,000 years ago, having descended directly from Australopithecus afarensis, the cranial capacity of Australopithecus garhi measured out to about 450 cm³. Still, those particular Pliocene hominans were able to make and use primitive Olduwan technologies, like the hammer and anvil, to aid in the acquisition of previously inaccessible fatty foods such as brain tissue and bone marrow.

2,440,000, in South Africa, other populations of Australopithecus aferensis started down a different path that would eventually give rise to Australopithecus africanus. In time, this species would produce Australopithecus sediba, which would inevitably go on to evolve into Homo gautengensis.

2,425,000 years ago, the summers began to get cooler, year by year, as the continents came closer and closer to their present positions. The climate was characterized by repeated glacial cycles which gradually led to several major extinctions and radical adaptations. For instance, the loss of body hair began to take place.

2,400,000 years ago, even though the South African lineage of hominans was going extinct, the East African line would remain extant, yet the evolutions both followed a strikingly similar pattern. In either case, there was a highly specialized Paranthrop that diverged from an Australopith that then gave rise to a highly adaptable member of the Homo genus, starting with the habilines in our ancestry.

2,350,000 years ago, Homo habilis stood no more than 1.3 meters tall, with disproportionately long arms compared to modern humans, and they had a less protruding face than the australopithecines. H. habilis’s brain capacity was 500 cm³. This meant that, H. habilis was a staple in the diet of large predatory animals such as Dinofelis, a large scimitar-toothed cat.

2,250,000 years ago, as testosterone levels continued to increase, this increased the strength and massiveness of the muscles of posture which further stimulated and reinforced habitual upright walking. The increase in testosterone also reduced the effects of estrogen on genital display, while, at the same time, increasing the growth of breasts. Thus, the signal for female sexual maturity switched from genital display to breast display.

2,100,000 years ago, Homo habilis and other species of ancient humans lived alongside ever diminishing populations of Australopithecus and Paranthropus species. In addition to this, the formation of the Congo River ultimately led to the speciation of the bonobo from the chimpanzee. This matriarchal species developed less prominent brow ridges, a black face with pink lips, small ears, wide nostrils, a slim upper body, narrow shoulders, a thin neck, and long legs compared to their closest relative.

2,000,000 years ago, Homo habilis had more modern-looking hands and feet which enabled them with greater dexterity. As a result, the ability to throw overhand served as an impetus for lateral refinements in the brain. All of these morphological changes made the hominans more proficient than other animals, so H. habilis was able to travel north and thrive, unlike the primates that lacked the brainpower and physical dexterity to exist in colder climates. Meanwhile, the Australopithecus genus went extinct.

1,950,000 years ago, Homo habilis had a brain volume of 600 cm³. At this point, the hominan brain had become large enough to allow for the development of highly complex social skills in conjunction with consistently noticeable whites in their eyes. This allowed them to convey a rich depth of meaning with nothing more than a glance. In addition to this, Homo habilis had fully mastered the Olduwan era tool case which included, but was not limited to, heavy pounding stones, large axes with a chopping-edge, and small flakes that could be used to scrape and slice.

1,900,000 years ago, Homo erectus gained the ability to walk extremely long distances because a ligament in the organism’s neck steadied their head and eyes. Additionally, elastic tendons worked like springs, and strong buttocks stabilized their torso when leaning forward into a stride. They could also travel further distances because the species possessed an incredibly efficient sweating system. As a result, they would sweat far more and pant far less.

1,825,000 years ago, Homo erectus stood about 1.8 meters and were more robust than modern humans, with a cranial capacity of 850 cm³. The species had a low and rounded braincase that was elongated from front to back, a prominent brow ridge, and an adult cranial capacity that was an average of twice that of the australopithecines.

1,800,000 years ago, Homo erectus evolved new facial musculature. This allowed for increased complexity of both the components of vocalization, including specific sounds, as well as the volume, pitch, tone, and emphasis of their calls. In this way, they became the first early human to fit squarely into the category of a hunter and predator and not as prey for larger animals.

1,775,000 years ago, the gender differentiation of male and female anatomy, as well as the specialization of gender tasks began to emerge. Since females had broader hips for child-bearing, women tended to spend more time attending to the tasks associated with the hearth. In contrast to this, males remained narrow hipped and roamed about as the hunters and defenders of the family.

1,650,000 years ago, many different types of hominans indulged in an array of prehistoric gene swapping. For all of their similarities, these divergent human species each had very different lifestyles. Some ate termites rather than the meat of animals and therefore were not in direct competition with each other. However, feuds and even bouts of cannibalism were not altogether uncommon amongst select populations.

1,500,000 years ago, Homo erectus tamed the flames caused by wildfires. As part of this, they put together a system of tending to the fire at night and subsequently carrying it through the day as they migrated. This gave rise to one of the first forms of ceremonial ritual, along with the religious reverence for an elemental force in nature. Fast calories from cooked food triggered a massive growth spurt, so they grew up to 2 full meters in height, and the reduced need for digestion allowed their intestines and rib cage to shrink.

1,450,000 years ago, the Acheulean Stone Age was well underway. All the while, the geographic distribution of Acheulian tools, and the people who made them was the result of climatic and ecological factors, such as glaciations and desertification. The earliest Acheulean assemblages contain numerous Olduwan-style flakes and core forms. In general, Acheulean tools were used for a variety of tasks including hacking wood from trees, digging up roots and tubers, butchering carcasses, and scraping hides.

1,440,000 years ago, H. habilis and H. erectus continued to live alongside the ever-diminishing populations of australopithecines. In addition to this, H. erectus also traveled thousands of miles into Europe and Asia over the course of several millennia, although they were limited to the lower and middle latitudes, even during interglaciations.

1,425,000 years ago, the distinctive oval and pear-shaped hand-axes of the Acheulean tradition attained such a high level of sophistication that the inventions became one of the earliest forms of art and economy in the world. They provided one of the earliest examples of an aesthetic sensibility in human prehistory.

1,000,000 years ago, as part of a very early migration of ancient humans out of Africa, Homo erectus had walked into and across Asia. There they came in contact with the largest apes to ever walk the Earth. Gigantopithecines were almost 2.7 meters in height, with a weight of up to 270 kg, which must have been utterly terrifying. The beast would have been absolutely massive compared to any prehistoric person.

900,000 years ago, Homo erectus observed stegodont herds swimming out to different islands, from the mainland of Southeast Asia. So, they fashioned together rudimentary bamboo rafts, using the stone hand axes they inherited from their ancestors. Then, they daringly ventured out, to the Indonesian island of Flores. There, the isolated Stone Age humans and stegodonts both gradually underwent insular dwarfism.

804,000 years ago, our ancestors split off from what would later become the Denisovans and Neanderthals.

650,000 years ago, environmental conditions in Africa allowed a variety of animals to become much larger than they are today. As such, one species of Pleistocene hominan, Homo heidelbergensis, grew in excess of 2 meters. This was nature’s attempt to push the envelope of human body size, so the species used up twice the amount of energy than that of a modern human.

640,000 years ago, Homo neanderthalensis split from Homo denisova, thereby giving rise to the Neanderthals and the Denisovans.

600,000 years ago, Homo heidelbergensis significantly contributed to a more sophisticated tool-making approach so there was a distinct transition in the artifacts made in Africa before and after this period, with the older group being thicker and less symmetric and the more recent being significantly streamlined.

400,000 years ago, the hominan brain stopped its slow trend toward increased size although at least one species did eventually acquire the wherewithal to openly communicate verbally. However, the degree to which the base of the skull was angled was not adequate enough for the larynx to move up and down, so the full command of articulate speech was still not possible.

350,000 years ago, the larynx and hyoid bone were sufficiently developed enough to allow humans to speak with a fully modern voice. As people began to live in bigger social groups and engage in large-scale coordinated hunting, their minds could no longer cope with the demands of life solely on the basis of their perceptual senses and limited cognitive abilities. As a result, a new level of linguistic intelligence emerged in the cerebral cortex.

340,000 years ago, social status continued to play an important role in the organization of kinship. By naming individuals and relationships, it became possible to articulate the rules of social interactions between one another. This made it easier to distinguish among close kin and individuals in other lineages.

325,000 years ago, the foundation for the modern nuclear family set about the gradual decline of communal living amongst the here-to-fore tribal people of that era. No longer would four or five families live together in bands.

300,000 years ago, Neanderthals had an enormous cranial capacity of 1,900 cm³. They were part of a separate Eurasian human lineage, which evolved in isolation and which shared a common ancestor with Homo sapiens in the Middle Pleistocene. In addition to this, Homo rhodesiensis lived throughout much of Africa. This hominan had a moderate cranial capacity of 1,100 cm³. It had a broad face, with a large nose, similar to Homo neanderthalensis.

250,000 years ago, the Mousterian tradition became a style of predominantly flint tools associated primarily with Homo neanderthalensis in Europe and Homo sapiens in Northern Africa and the Near East, dating to the middle part of the Old Stone Age. This consisted mainly of hand-axes, racloirs, and points.

230,000 years ago, Neanderthals adapted to cold climates, having short limbs to conserve heat and broad noses to cool them down to prevent them from making any sweat that would then freeze. As a result, the harsh climate changed their outlook on life.

200,000 years ago, anatomically modern Homo sapiens emerged for the first time in prehistory. They lived along the Omo River in Ethiopia.

150,000 years ago, the most recent female ancestor common to all mitochondrial lineages of extant humans lived in East Africa, about ten thousand generations ago.

142,000 years ago, the most recent common ancestor from whom all male human Y chromosomes are descended lived in East Africa.

100,000 years ago, in the limited food environment on Flores, H. erectus had evolved a smaller body size becoming H. floresiensis. It had a remarkably small brain with a volume of 380 cm³. Nonetheless, the size of their dorsomedial prefrontal cortex, an area of the brain associated with higher cognition, was about the same size as that of modern humans.

90,000 years ago, coastal hominans lived in caves near the water in Africa, so they didn’t have to hunt or scavenge. All they had to do was fish, and the abundance of omega-three fatty acids made it easier for signals to jump the gap between neurons in their brains. This made them much more contemplative creatures.

85,000 years ago, reverence of the impressive activities of nature progressed into full-blown animism, and the first shamans learned how to enter trances and use herbs to cure people or bring about divine visions. Those indigenous Africans were the first people to be regarded as having access to, and influence in, the domain of the supernatural. So, they became special helpers of the community, using their newly acquired talent to perform magic.

78,000 years ago, adornments quickly became very fashionable. This took the form of culturally unique clothing, jewelry, and many other forms of personal expression, like tattooing and scarification. Through transitional rites of passage, each major change in life was incorporated into the domain of the sacred. This development of more and more memes led to specific dialects, distinctive clothing and body markings, and tribally divergent social structures.

73,000 years ago, one of the Earth’s largest eruptions occurred in Indonesia at Mount Toba. The change in temperature created a bottleneck in the population of Homo sapiens. Meanwhile, nearby hominan populations, such as Homo erectus soloensis in Java and Homo floresiensis in Flores survived because they were upwind of Toba.

60,000 years ago, in search of better sources of food, Homo sapiens traveled east until they reached the Pacific Ocean, and the mitochondrial haplogroups M and N appeared as people participated in the migration out of Africa, interbreeding with the Neanderthals and other people they encountered along the way.

55,000 years ago, the frequent use of animal hides as clothing allowed head lice to evolve into body lice once people spread out into cooler regions. Hominans were also becoming more and more consumed with spirituality and religiosity. This led to elaborate theatrical portrayals in which people dressed as, and mimicked, the animals that they wished to coexist with or have dominion over.

54,000 years ago, Homo sapiens first arrived in Australia on bamboo rafts from Indonesia. Then, the Aborigines began systematically burning down the forests. As a result, many of the land-dwelling fauna went extinct. In all, fifty-some species died off from the devastating destruction.

50,000 years ago, humans migrated to South Asia and the mitochondrial haplogroups U and K appeared. People also developed highly advanced stone tool-making techniques around this time. The most advanced stone tools exhibited distinct and consistent regional differences in style, reflective of a high degree of cultural diversity.

45,000 years ago Homo sapiens made it to Flores. Form that time on, H. floresiensis lived contemporaneously with H. sapiens on that island. Hobbits and humans even learned to speak each other’s language.

44,000 years ago, people migrated into Europe from central Asia and the Middle East, where they encountered Neanderthals, for better or worse. Similarly, large numbers of Homo sapiens were migrating to Australia and Europe.

43,000 years ago, Homo sapiens used caverns and caves as ritual chambers, climbing deep inside of mountains or far down into the ground to build portals to the spirit world. These were among the earliest sacred spaces that our ancestors used as places of worship, where they would chant archaic incantations and become possessed by the spirits of their ancestors and the animals they depended on.

42,000 years ago, several human populations dug graves to remove corpses from habitation areas, in an attempt to avoid attracting scavengers and to participate in the natural grieving process associated with the loss of loved ones. This macabre meme became rather widespread fairly quickly.

36,000 years ago, dogs became man’s best friend, when Canis lupus familiaris was tamed by Homo sapien sapiens. The least aggressive wolves went from the fringes of our communities all the way into our homes, becoming humanity’s first pets.

30,000 years ago, Homo sapiens had to build permanent homes to shelter from the increasingly longer winters. Then, in the summer, they followed the herds and lived in mobile tents. They also used pits dug in the permafrost as natural freezers, and hearths in which hot stones were used to heat water in skin-lined pits.

27,000 years ago, although humans and Neanderthals had lived together for thousands of years, more or less attempting to maintain their distinct cultural identities and genetic lineages, the Neanderthals eventually went extinct.

25,000 years ago, in Europe, people were still hunting and gathering rather than farming. So, hunter-gatherer groups often fluctuated seasonally in size between that of nuclear family-sized groups in times of resource scarcity, and large aggregations of multi-family units, containing dozens of individuals, during periods of resource abundance.

20,000 years ago, was a time that marked the beginning of the Epipaleolithic period of prehistory, which was the first part of the Holocene epoch. This was the time of the Younger Dryas near the end of the Ice Age when there was a period of sudden cooling and a return to glacial conditions. This served as a highly transformative time in the development of our species.

12,800 years ago, the Chukchi became the first settlers to arrive in North America. They paddled east along an exposed land bridge that connected Siberia to Alaska. Then, they used the rivers, and other waterways, to travel inland. In this way, a number of Native American populations, such as the Navajo, spread into and across the continent, in a relatively short period of time.

12,500 years ago, a catastrophic volcanic eruption on Flores was responsible for the demise of Homo floresiensis. So, after having interacted with each other for millennia, the generations of history between humans and hobbits ended, in one fell swoop.

12,000 years ago, the Natufians founded a village at Jericho. They chose the lushest oasis in the Jordan Valley because the Levant hosts more than a hundred kinds of cereals, fruits, nuts, and other edible parts of plants. This was important because these were affluent hunter-gatherers who were becoming farmers and shepherds, complete with sheepdogs.

11,500 years ago, advanced megalithic societies began producing extraordinary stone structures in order to access the spirit world and harness unseen forces in a new way. The temples at the Giza plateau on the Nile in Egypt and Potbelly Hill on the Euphrates in Turkey were both used religiously by Neolithic pilgrims.

11,000 years ago, the transition from foraging to farming involved a reduced availability of animal protein. This move from horticulture to agriculture occurred in conjunction with an increased reliance on a limited number of domesticated plants. On average, many of these plants offered a poor nutritional base. So, stunted growth was common among the first civilizations.

10,000 years ago, after generations of experience, the Agricultural Revolution was well underway across the globe. As the climate, vegetation, and fauna became increasingly more modern, early human populations, all around the world, began to control the breeding of more and more plants and, to a lesser extent, animals.

9,500 years ago, when the Upper Paleolithic ended and the Neolithic began, clay and plaster statues were first being molded in Jericho and other major settlements.

9,000 years ago, incised “counting tokens” were created in the Neolithic fertile crescent of Asia, in the early Near East. They were clay symbols of multiple shapes used to count, store, and communicate economic data. This was the first form of currency.

8,000 years ago, the Halaf culture flourished in Mesopotamia. This was when copper was being used in the Near East for the very first time. Along with this, the first batches of wine were being produced in Georgia for the first time as well.

7,000 years ago, the first true city was established on the southernmost tip of a conglomeration of Sumerian towns that would grow larger as temples got taller. Eridu was the first port in the world and the home of the original dynastic king who lived in the first palace in the world.

6,500 years ago, it became necessary to justify a ruler’s authority based on divine selection. On occasion, the monarch himself was actually considered holy and worthy of worship. However, in order to maintain such authority, it became necessary to establish new forms of law based primarily on individual and state-administered revenge.

6,000 years ago, the Mesopotamian metropolis of Ur was situated on early trade routes, which ran along the banks of the Tigris and Euphrates, as well as the Persian Gulf. Since urbanization depended on irrigation, this made it possible to grow bushels of wheat and barley in record numbers. This led to a major increase in population.

5,000 years ago, most Homo sapiens ceased to grow or raise their own food, which meant that farmers needed to get the crops to everyone else. This required a new job, and so on and so forth. Thus, the first empire builders came to power in ancient Sumeria. This created the need for a complex record-keeping system, which placed a novel demand on society that eventually led to the invention of writing, and the rest is history….


Contents

The remains were discovered on the Indonesian island of Flores by an Australian-Indonesian team of archaeologists in 2003. Archaeologist Mike Morwood and colleagues were looking for evidence of the original human migration of H. sapiens from Asia to Australia. [1] [3] They were not expecting to find a new species. They were surprised at the discovery of a nearly complete skeleton of a hominin.

Excavations done after that found seven more skeletons, originally thought to be from 38,000 to 13,000 years ago. [2] An arm bone which they think belongs to H. floresiensis was dated at about 74,000 years old. The specimens are not fossilized and have "the consistency of wet blotting paper" once exposed. The bones had to be left to dry before they could be dug up. [4] [5] :86

However, more extensive stratigraphic and chronological work pushed the most recent evidence of their existence back to 50,000 years ago. [6] [7] Their skeletal material is now dated to from 100,000 to 60,000 years ago. Stone tools recovered alongside the skeletal remains were from archaeological horizons ranging from 190,000 to 50,000 years ago. [8]

Researchers hope to find preserved mitochondrial DNA to compare with samples from similarly unfossilised specimens of Homo neanderthalensis and H. sapiens. [4]

This hominin is remarkable because it has a small body and brain. There are also a lot of stone tools found in the cave. The tools are of a size that could be used by the 1 meter tall human. They are dated from 95,000 to 13,000 years ago. They are found in the same archeological layer as an elephant of the extinct genus Stegodon. The hobbit might have hunted this elephant. The elephant would have been very common throughout Asia during the Quaternary. [2] Other animals that lived on the island at that time were giant rats, Komodo dragons, and even larger species of lizards. [9] Homo sapiens reached the region by around 45,000 years ago. [10]

Archaeologist Mike Morwood and colleagues who found the remains say they think the individuals belong to a new species, H. floresiensis, in our human genus Homo. [1] [3] The discoverers also say that H. floresiensis might have lived at the same time as modern humans (Homo sapiens) on Flores. [11]

Not everyone agrees that this is a new species. Indonesian anthropologist Teuku Jacob suggested that the skull of LB1 was a modern human with microcephaly. This is a disorder that causes the bones of the head to stop growing. Another study says that perhaps the individuals were born without a working thyroid gland, which would result in the small size of the hominins because of a disorder called myxedema. [12]

Two studies of the bones published in 2007 both reported evidence to support species status for H. floresiensis. A study of three bits of bones from the hand (carpals) showed that they were similar to the carpal bones of a chimpanzee or an early hominin such as Australopithecus. They were also different from the bones of modern humans. [13] [14] A study of the bones and joints of the arm, shoulder, and legs also concluded that H. floresiensis was more similar to early humans and apes than modern humans. [15] [16] In 2009, the publication of a cladistic analysis, [17] and a study comparing body sizes, [18] gave further support for the theory that H. floresiensis and Homo sapiens are separate species.


Identity of mysterious 'Hobbits' possibly found

The extinct human lineage nicknamed "the hobbit" may not be a distant relative of modern humans as previously thought. Instead, hobbits may be members of the mysterious close relatives of modern humans known as Denisovans, and may have interbred with ancestors of modern humans on the islands of Southeast Asia, researchers say.

Although modern humans, Homo sapiens, are now the only surviving human lineage, other human species once roamed across Earth. For instance, previous research suggested Homo erectus, the most likely ancestor of modern humans, made its way out of Africa by at least 1.8 million years ago. In contrast, modern humans may have only begun migrating out of Africa about 200,000 years ago.

In the past 20 years, researchers have discovered many new branches of the human family tree on the islands of maritime Southeast Asia, which includes Brunei, Indonesia, Malaysia, the Philippines, Singapore and East Timor. These human ancestors include the extinct species Homo floresiensis, often known as "the hobbit" for its miniature body, as well as the even smaller Homo luzonensis. Both species survived until about 50,000 to 60,000 years ago, meaning they may have lived in the region at the same time as modern humans.

Recently, scientists have detected signs that extinct groups of humans not only overlapped timewise but also had sex with the modern humans of maritime Southeast Asia. For example, fossil DNA suggests the ancestors of modern Papuans and South Asians interbred with a southern branch of the mysterious Denisovans, who were close relatives of Neanderthals.

But even though modern people in these regions have relatively high levels of Denisovan DNA, suggesting significant interbreeding, no Denisovan fossils have been found in the region &mdash the only traces of this enigmatic group found so far were a finger bone and jawbone unearthed in Siberia and Tibet.

Now, researchers suggest that either the hobbit H. floresiensis or its smaller cousin H. luzonensis or both may actually be southern Denisovans. They detailed their findings online March 22 in the journal Nature Ecology and Evolution.

To shed light on the prehistory of maritime Southeast Asia, the study researchers analyzed more than 400 modern human genomes from across the world, including more than 200 from the islands of Southeast Asia and New Guinea. Scientists hunted specifically for genetic sequences that were significantly different from those usually detected in modern humans, because such DNA may have come from extinct human lineages such as H. floresiensis or H. luzonensis.

The new study confirmed prior work that found relatively high levels of Denisovan ancestry in people of maritime Southeast Asia, New Guinea and Australia &mdash up to 3% to 6% of their DNA comes from Denisovans. It did not show evidence of interbreeding between modern humans and older lineages, such as Homo erectus.

The researchers also found traces of highly divergent genetic sequences in Denisovan DNA &mdash extracted from specimens found in Siberia &mdash that may have come from very distant relations of modern humans, which might suggest Denisovans could have interbred with an archaic human lineage such as H. erectus about 1 million years ago, before Denisovans split into southern and East Asian branches.

So what might these new findings suggest? One possibility is that H. floresiensis and H. luzonensis are very distant relatives of modern humans as currently thought, evolving from H. erectus or a similarly ancient lineage, and that Denisovans are a completely separate lineage. In this scenario, neither of these smaller-sized Homo species would have interbred with either Denisovans or modern humans.

Another more extraordinary possibility is that H. floresiensis and H. luzonensis may differ significantly from modern humans in terms of anatomy, but either or both might be closer relatives of modern humans than often suggested. In this scenario, these human species might not have differed from modern humans as much genetically as previously thought, explained study author João Teixeira, a population geneticist at the University of Adelaide in Australia. If so, either or both of these lineages might be examples of southern Denisovans, in which case, they would have interbred with the ancestors of the modern humans of maritime Southeast Asia, potentially explaining the high levels of Denisovan ancestry found in modern people there, he noted.

"Maybe H. floresiensis and H. luzonensis are not very divergent super-archaic groups as we currently assume," Teixeira told Live Science.

However, not everyone who was part of the study agreed with that conclusion. Study co-author Chris Stringer, a paleoanthropologist at the Natural History Museum in London, noted archaeological evidence suggested H. floresiensis and H. luzonensis were living in maritimeSoutheast Asia since at least 700,000 to 1 million years ago, long before the Denisovan lineage first evolved. Given that, he argued the hobbit and its cousin may be too ancient to be the southern Denisovans.

However, the oldest supposed fossils associated with H. floresiensis and H. luzonensis in the region may not actually have belonged to these species, Texeira noted.

Instead, those fossils may be traces of an earlier group. So it might still be possible that either H. floresiensis or H. luzonensis &mdash or both &mdash arrived later to their respective isles and could still potentially be Denisovans.

This suggested connection between hobbits and Denisovans remains uncertain because scientists have yet to successfully analyze DNA from any fossils of H. floresiensis or H. luzonensis, Teixeira cautioned.

"It's hard for DNA to preserve in the tropics," he said. "At the moment, this idea is only speculation. But H. floresiensis and H. luzonensis are definitely at the right place at the right time to be southern Denisovans."

To help fill in the missing branches of the human family tree in the islands of Southeast Asia, researchers should not only continue searching for DNA in human fossils from this region, but also look for fossils in other areas such as Australia, Teixeira said.

All in all, Teixeira predicted, "the next big find in human evolution is due to occur in island Southeast Asia."


Southeast Asians Carry DNA of ‘Mysterious Southern Denisovans’

The hominin fossil record of Island Southeast Asia (ISEA) indicates that at least two super-archaic species, Homo luzonensis and Homo floresiensis, were present around the time anatomically modern humans arrived in the region 50,000-60,000 years ago. In new research, an international team of scientists examined more than 400 modern human genomes to investigate ancient interbreeding events between super-archaic and modern human species. Their results corroborate widespread Denisovan ancestry in ISEA populations, but fail to detect any substantial super-archaic admixture signals compatible with the fossil record.

A portrait of a juvenile female Denisovan based on a skeletal profile reconstructed from ancient DNA methylation maps. Image credit: Maayan Harel.

ISEA, also known as Maritime Southeast Asia, is a region that includes the countries of Brunei, Indonesia, Malaysia, the Philippines, Singapore, and East Timor.

It hosts a unique and diverse fossil record of hominin presence throughout the Pleistocene epoch.

The island of Java in modern Indonesia marks the southeastern extent of the range of Homo erectus, the first hominin species thought to have successfully dispersed outside Africa, where it maintained a presence from 1.49 million years ago until 117,000-108,000 years ago.

At least two additional endemic species lived in ISEA during the Pleistocene and are likely to have survived until the arrival of anatomically modern humans over 50,000 years ago: Homo floresiensis on Flores, in the Lesser Sunda Islands (also part of modern Indonesia), and Homo luzonensis on Luzon, in the northern Philippines.

Recent interpretations suggest that Homo floresiensis is either a close relative of Homo erectus, or alternatively represents an even more archaic species of Homo that independently reached ISEA in a separate dispersal event out Africa.

The current classification of Homo luzonensis is also uncertain the available specimens share similarities with various hominin species including Australopithecus, Asian Homo erectus, Homo floresiensis and Homo sapiens.

This is an artist’s reconstruction of Homo erectus. Image credit: Yale University.

In the new study, University of Adelaide’s Dr. João Teixeira and colleagues examined the genomes of more than 400 modern humans, including over 200 from ISEA, to investigate the interbreeding events between the super-archaic species and modern human populations who arrived at ISEA 50,000-60,000 years ago.

In particular, they focused on detecting signatures that suggest interbreeding from deeply divergent species known from the fossil record of the area.

Their results showed no evidence of interbreeding nevertheless, they were able to confirm previous results showing high levels of Denisovan ancestry in the region.

“While the known fossils of Homo erectus, Homo floresiensis and Homo luzonensis might seem to be in the right place and time to represent the mysterious southern Denisovans, their ancestors were likely to have been in Island Southeast Asia at least 700,000 years ago,” said Professor Chris Stringer, a researcher at the Natural History Museum, London.

“Meaning their lineages are too ancient to represent the Denisovans who, from their DNA, were more closely related to the Neanderthals and modern humans.”

Reconstruction of Homo floresiensis. Image credit: Elisabeth Daynes.

“These analyses provide an important window into human evolution in a fascinating region, and demonstrate the need for more archaeological research in the region between mainland Asia and Australia,” said Professor Kris Helgen, director of the Australian Museum Research Institute.

“We know from our own genetic records that the Denisovans mixed with modern humans who came out of Africa 50,000-60,000 years ago both in Asia, and as the modern humans moved through ISEA on their way to Australia,” Dr. Teixeira said.

“The levels of Denisovan DNA in contemporary populations indicate that significant interbreeding happened in ISEA.”

“The mystery then remains, why haven’t we found their fossils alongside the other ancient humans in the region? Do we need to re-examine the existing fossil record to consider other possibilities?”

The findings were published in the journal Nature Ecology and Evolution.


Homo floresiensis

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Conflicting interpretations and debates surround the remains of these tiny humans from Indonesia. H. floresiensis are not our ancestors but their unusual features and recent survival indicates our human family tree is more complex than once thought.

Background of discovery

The human remains date from about 100,000 to 60,000 years old, but archaeological evidence (mostly associated stone tools) suggests H. floresiensis lived at Liang Bua from at least 190,000 to 50,000 years ago (recent dates published in Nature, March 2016). These dates make it one of the latest-surviving humans along with Neanderthals, Denisovans and our own species H. sapiens.

Their disappearance coincides with that of other local fauna such as the Stegodon, the giant marabou stork and various vulture species. The loss was originally attributed to a volcanic eruption that occurred on Flores approximately 12,000 years ago but the recently published dates nullify this suggestion. Instead, it is now considered possible that the arrival of modern humans played a role. Although there is no evidence of modern humans in Liang Bua cave until 11,000 years ago, our species was moving through the region about 50,000 years ago.

Important discoveries

A joint Australian-Indonesian team, looking for evidence of the early migration of Homo sapiens from Asia to Australia, stumbled on the remains of a small human in the cave of Liang Bua, Flores, in 2003. The discoverers (Peter Brown, Michael Morwood and colleagues) argued that a variety of primitive and derived features identified the remains as that of a new species. Descriptions of some of the remains and the new species designation were published in October 2004.

The remains include a largely complete skeleton with skull (LB1) and parts of at least eleven other individuals. These remains come from different levels and range in date from 100,000 to 60,000 years old. An arm bone, from a deeper level and dating to about 74,000 years old, is provisionally assigned to H. floresiensis. A more accurate designation is difficult to make as LB1 lacks an arm bone to make comparisons with.

Stone tools have been recovered from a number of levels and range in dates from 190,000 to 50,000 years old.

As the remains are relatively young and unfossilised, researchers hoped to find mitochondrial DNA. Initial efforts were unsuccessful, but the research continues.

Excavations from 2007 to 2014 used new dating techniques to understand the complex cave stratigraphy. The publication of the revised dates (in Nature, March 2016) led to a reassessment of the causes of the species' extinction.

  • LB1 – type specimen discovered in September 2003. It is unfossilised. The remains consist of a fairly complete skull and partial skeleton including leg bones, parts of the pelvis, hands and feet, and some other fragments. It is assumed to belong to a female aged about 30 years old. She stood about 1 metre tall, had a brain volume of about 380-420cc and weighed about 25 kilograms. The body was not deliberately buried but covered soon after death by fine sediments, when still partially fleshed.
  • LB6 – a partial skeleton belonging to a shorter individual than LB1. It has a more V-shaped jaw and is assumed to be a child, possibly only 5 years old.

In 2016, scientists announced they had discovered the lower jaw and teeth from at least one adult and possibly two children of what may be an early form of H. floresiensis. These fossils were found at Mata Menge, about 70kms east of Liang Bua cave on Flores and date to 700,000 years old.

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What the name means

The genus name Homo is the Latin word for ‘human’ or ‘man’. The species name floresiensis recognises the island of Flores in Indonesia where the remains were found.

They are commonly referred to as the ‘hobbits’, after the Lord of the Rings characters, in reference to their small size and large feet.

Distribution

All remains come from the cave of Liang Bua on the island of Flores in Indonesia. Flores lies towards the eastern end of the Indonesian island chain.

Flores has always been separated from mainland Asia - even at low sea levels the water-crossing was at least 24 kilometres. It is known that other animals reached Flores by swimming or floating on debris. How or when H. floresiensis reached the island is unknown.

Relationships with other species

When first discovered, it was suggested that H. floresiensis was possibly descended from Javanese H. erectus. However, more detailed analysis of skeletal remains has uncovered traits more archaic than Asian H. erectus and more similar to australopithecines, H. habilis or the hominins from Dmanisi in Georgia (classified as Homo ergaster or Homo georgicus). Most scientists that accept H. floresiensis as a legitimate species now think its ancestor may have come from an early African dispersal by a primitive Homo species similar in appearance to H. habilis or the Dmanisi hominins. This means that it shared a common ancestor with Asian H. erectus but was not descended from it. Cladistic analysis supports the lack of a close relationship with H. erectus.

The recently announced (2016) discovery of a jawbone and some teeth from Mata Menge on Flores help fill in the time gap between H. floresiensis and its earlier ancestor. Stone tools that may have been made by H. erectus (or a similar species) were discovered on Flores. These date to 840,000 years ago, so indicate that a hominin species was probably living on the island at that time.

Whatever the origins of the ancestral population, it is accepted that the population underwent long term isolation on the island and some insular dwarfing (although they were probably small to start with) which resulted in an endemic ɽwarf' species H. floresiensis. This is a common phenomenon seen in other mammals in similar environments.

Modern humans arrived in Indonesia between 55,000 and 35,000 years ago, and may have interacted with H. floresiensis, although there is no evidence of this at Liang Bua.

Interestingly, local legends exist in Flores of the Ebu Gogo – small, hairy, cave dwellers similar in size to H. floresiensis. It is suggested that perhaps the hobbits survived longer in other parts of Flores to become the source of these stories.

A new species or a small Homo sapiens?

Doubts that the remains should be classified as a new species are voiced by a number of scientists, some vehemently. They claim that the remains come from a modern human with some sort of physical disorder. The alternate suggestions include:

  • the remains are from a very small human that suffered from some type of disease that causes microcephaly, a developmental disorder of the brain that causes it to be much smaller than normal
  • the remains are from a human with Laron syndrome, a disorder that results in pituitary dwarfism (published in 2007 by a team from Tel Aviv University, Israel)
  • the remains are those of dwarfed Homo sapiens similar to the small-bodied humans that inhabited the Micronesian island of Palau between 1400 and 3000 years ago. These people shared some features with the H. floresiensis specimens, but not all. Detailed analysis of the Palau specimens is unlikely to settle arguments over the status of H. floresiensis but they do suggest that some of its unusual features could be due to environment rather than ancestry.

Many of those rejecting the new species status focus only on the remains of LB1, and ignore the other remains that show many of the same characteristic features. In contrast, a number of recent analyses of the skull, face, foot and wrist have confirmed the many unusual primitive features of H. floresiensis remains and stated that they are more similar to australopithecines. For instance:

  • a cladistic analysis done in 2009 supported H. floresiensis as a separate species (Journal of Human Evolution Online as of 4 August 2009)
  • a study using 3D-morphometrics showed that the skull of LB1 differs significantly from all H. sapiens skulls, including those of small-bodied individuals and microcephalics, and is more similar to the skull of Asian Homo erectus (Baab & McNulty, Journal of Human Evolution, 2008)
  • a team of experts created detailed maps of imprints left on LB1’s braincase and concluded that the remains belonged to a new species. Comparisons of different parts of the brain showed it was nothing like a microcephalic's and is also different from modern humans. The endocasts also revealed that parts of the frontal lobe and other features were consistent with higher cognitive processes. (Falk et al, PNAS, January 29, 2007,)
  • H. floresiensis wrist is almost indistinguishable from an African ape or early hominin wrist and is nothing like those of modern humans or Neandertals. The distinctive shapes of wrist bones form during pregnancy and as most pathologies and growth disorders affect the skeleton well after that, this demonstrates that the remains come from a new Homo species. (Matt Tocheri et al, Science 21 September 2007)
  • studies on brain-size reduction in dwarf hippos from Madagascar revealed that brains shrank to volumes well below predicted sizes. This refutes a key argument used by sceptics who claim the brains are too small for dwarfing alone to be the cause (hence they cite microcephaly or similar disorders), (Weston & Lister, Nature, 7 May 2009)

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Taking into consideration the new timeline of H. floresiensis and its geological location- is insular dwarfism still a valid hypothesis? With reference to insular dwarfism from Flores and examples of extant primate populations on islands today

Taking into consideration the new timeline of H. floresiensis and its geological location- is insular dwarfism still a valid hypothesis? With reference to insular dwarfism from Flores and examples of extant primate populations on islands today

Since its initial discovery in 2004, Homo floresiensis has been the topic of much debate. The discovery led to a new wave of understanding in hominin evolution that challenged views on the ever more complicated history of our genus. H. floresiensis remains unique due to a combination of factors its isolated location, age (as the earliest evidence of hominins crossing the Wallace line) and morphology (notable for its diminutive size), but fundamentally it is still questioned how H. floresiensis came to be on the island of Flores, in regards to the lineage in which these hominins descend from. The recent discovery of Homo luzonensis bears many similarities to H. floresiensis (concerning its geographical location and aspects of its puzzling morphology), but remains younger in age [Détroit et al., 2019]. In regard to the question of morphology, Brown and his colleagues state in their first publication on H. floresiensis that ‘a prolonged period of isolation may have resulted in the evolution of an island endemic form’ [Brown et al., 2004]. Similarly, faunal remains found on Flores, and multiple island settings show examples of why island dwarfism and gigantism prevail . By analysing the faunal remains and the stratigraphic layers these fossils were found in and researching examples of insular dwarfism in extant species today, paleoanthropologists can begin to theorise about the life of H. floresiensis , the selective pressures that led to its unique morphology and how it came to be on Flores .

Other species on Flores that show recorded examples of insular dwarfism can potentially give insights into the environment and the evolution of H. floresiensis . A clearly defined example in the fossil record is that of Stegodon florensis insularis and its presumed direct ancestor Stegodon florensis florensis . S. f. florensis ’ fossil records date to around 1 ma- 800 ka [Morwood et al., 1998 Van Den Bergh et al., 2008 Puspaningrum, 2016], and its insular descendant, only found on Flores is dated in association of H. floresiensis remains at Liang Bua at 74 ka [Morwood et al., 2004 Sutikna et al., 2016]. This indicates a span of more than 600 ka for insular dwarfism to occur in the “intermediate to large-sized Stegodon florensis ” to the S. f. insularis fossil with molars being “on average 30 per cent smaller in linear dimensions” than the former [Van Den Berger et al., 2008] and seemingly no change in size of S. f. florensis found at Mata Menge which spans 200 ka.

A conundrum we face when analysing Stegodon is the comparison of speed of dwarfism with

30 percent reduction in linear molar size [Van Den Bergh et al., 2008]. This reduction occurs over 600 ka from S. f. florensis to S. f. insularis whereas H. floresiensis size reduction from a Java H. erectus is observed to be in less than 300 ka. Brumm and colleagues [2016] notes this rapid change, unveiling the discovery of another group of small hominin fossils at Mata Menge, also presumed to be H. floresiensis . This assumption of rapid dwarfism is based on the stone tool artefacts at Wolo Sege dated to 1 ma [Brumm et al., 2010] and their presumed makers- the larger bodied H. erectus who are suggested to be the direct ancestor of H. floresiensis [Van den Bergh et al., 2016]. Revised dating for the earliest fossil evidence of hominins on Java dates to 1.4 ma [Morwood et al., 2003] with a single maxilla dated to 1.5 ma [Zaim et al., 2011] and all are generally attributed to H. erectus with no evidence of any other hominins around this geographical location in the Early Pleistocene. By 700 ka we are already seeing a dwarfed species, of similar estimated size to H. floresiensis at the Mata Menge site in the So’a Basin [Van den Bergh et al., 2016]. This perhaps is initially surprising considering the rapid dwarfism that is presumed to have occurred in H. floresiensis is considerably quicker than the Stegodon dwarfing. The S. f. florensis remains from Mata Menge span 200 ka from 1 ma- 800 ka without significant change in body size, despite “…a change of vegetation cover occurr[ing] around the earliest record of Stegodon florensis ” [Puspaningrum, 2016].

In fact, this change in vegetation cover and other environmental change can potentially tell us a great deal about insular dwarfism in both Stegodon and H. floresiensis . S. f. florensis fossils show a range of C3-C4 mixed to predominantly C4 diets suggesting a potential shift from “more open vegetation feeding habitat such as woodland to savannah” which seems to concur with the increasing aridity in the Middle Pleistocene [Puspaningrum, 2016]. S. f. insularis also follows this pattern with a predominant C4 diet, suggesting it is a highly specialized grazer [Puspaningrum, 2016]. This matches the data suggesting the first appearance of S. f. florensis coincides with a savannah-like glassland on Flores at around 0.8ma [Puspaningrum, 2016]. This potential shift in diets gives insights into environmental change on Flores and helps provide a better understanding of H. floresiensis ’ potential diet. To date, no isotopic analysis has been performed on H. floresiensis fossils. S. f. insularis fossils were found in association with H. floresiensis at Liang Bua, with signs of cut marks and even charred bone fragments, suggesting at least a partial scavenging diet for the hominins. This shift from C3 to C4 diet that occurs in S. f. florensis at around 1 ma [Puspaningrum, 2016] can be mapped by the coinciding appearance of hominins on Flores [Brumm et al., 2010] and may indicate a shift in diet due to a changing climate or limited resources, which could have been a strong evolutionary pressure for the ancestors of H. floresiensis to adapt quickly and dramatically in order to survive in the environment. This could be a key indicator and strong selective pressure linked to the small stature of H. floresiensis. This dwarfing could be indicative of the selection pressures and that other features of the hominins were altered in additional ways perhaps not anticipated for a more recent hominin, but essential for the adaptive niche of the island environment. However, analysis of H. floresiensis ’ foot, as an example, has provided an alternative hypothesis that its morphology must have come from a more primitive ancestor than H. erectus [Jungers et al., 2009 Lieberman, 2009]. Much of H. floresiensis ’ features appear more primitive, but given the small fossil record we have of hominins around Indonesia at 1 ma it may be that these primitive features were still retained in some later hominins like that of H. erectus . It is also possible for these primitive looking features to be adaptive niches for the environment- as we have seen in another hominin species as recently as 50 ka showing features that seem to have morphological similarities with Australopithecus that are generally assumed to have retained, at least in part, adaptation for climbing/suspension [Detroit et al., 2019 Tocheri, 2019].

Another thing to consider when comparing H. floresiensis to other examples of insular dwarfism, particularly ones outside of our own genus, Homo , is the comparatively long gestation period and presumed long inter-birth intervals with H. floresiensis . Gestational periods and lifespan of dwarfed species seem to parallel their larger relatives [van der Geer, 2014]. Using our closest living relatives and Modern humans as models. Chimpanzees average gestation period is 253 days (8.3 months) [Tomilin, 1936] and humans is at 9 months with weaning in hunter gatherer communities occurring around 3 years [Konner and Worthman, 1980], it is possible to estimate how long insular dwarfism in H. floresiensis could have taken strictly looking at size reduction and not at the other morphological changes. These models of chimpanzee and human gestation and weaning periods would have considerably increased time for insular dwarfism to take effect, comparatively to other animals affected by insular dwarfism. An example of this is Lister’s paper on red deer in Jersey which had 56% reduction in limb bone diameter and six times reduction of weight in 6 ka or less [1989]. Aiello and Key’s study on H. erectus ’ ‘reproductive scheduling’ also infers an increased energy expenditure along with increasing gestation periods to previous hominins (female Australopithecines are estimated to have been 50% lighter on average to female H. erectus ), although they estimates potential reduced birth intervals as a benefit for increased reproductive output [2002]. Stegodon would also have had increased gestation periods. As Elephantidaes are the only surviving family of the Proboscideans, they provide the closest estimate for Stegodons’ gestational period Elephants have a 22 month gestational period and an ‘intercalving interval of 4–8 years’ [Allen, 2006]. When taking this into consideration, if gestation periods are consistent with their larger distant relatives, it seems likely S. f. florensis would have taken considerably more time to dwarf compared to H. floresiensis , which would likely explain the significantly less time insular dwarfism took to occur in H. floresiensis .

Much work has previously been done on large mammalian species and the trends of insular dwarfism, but in contrast little has been researched on closer relatives of hominins. However, In 2007 Bromham and Cardillo reported their findings on examples of primates inhabiting small, isolated islands to help interpret H. floresiensis ’ skeleton. Primates from their study did seem to follow the ‘island rule’ where ‘all small island primate species (less than 5 kg…) are larger than their closest mainland relatives, and all other island species are smaller than their closest mainland relatives’ [Bromham and Cardillo, 2007]. However, Bromham and Cardillo report ‘the three largest island [primate] species (over 7 kg) are 52, 61 and 80% of the size of their mainland counterparts’ compared to H. floresiensis having an estimated 52% of the mass of Java H. erectus [2007].

It was also suggested that the LB1 specimen found at Liang Bua in Flores had a cranial capacity too small to warrant a place in the Homo genus. Falk [2005] has argued the body size of H. floresiensis in relation to cranial size is most similar to Australopithecus , despite its cranial morphology which has similarities to H. erectus , suggesting the fossil remains may be pathological. However, further analysis suggests that H. floresiensis ’ skull length is within relative range expected by dwarfed primate standards [Bromham and Cardillo, 2007] and along with postcranial morphology should be considered a new species. This comparison with other isolated primates and the increasing number of postcranial fossils of H. floresiensis in two locations is good evidence towards the island dwarfism theory, as the morphological differences observed post-cranially can rule out any indication of a modern human pathological specimen or population.

Stone tools have been found in association with hominin remains at both Mata Menge [Morwood et al., 1997 Brumm et al, 2006 Brumm et al., 2010a] and Liang Bua [Moore et al., 2009 Brumm et al., 2006]. But additional stone tools were discovered in Wolo Sege as described by Brumm et al. and are the oldest known evidence of hominins on Flores dated to 1 ma [2010]. The size of the raw materials found at Wolo Sege are between 40-220mm, with an average maximum dimension of 78.66 mm [Brumm et al., 2010]. The majority of the lithics at Wolo Sege are similar in size and production to the other lithics found at Mata Menge [Brumm et al., 2010] which in turn show great similarities to the stone tools found at Liang Bua [Brumm et al., 2006]. However, some of the raw materials presumably used for lithics found at Wolo Sege (220mm) seem incompatible for the estimated size of this hominin who stood at just over 1m tall [Brown et al., 2004 Morwood et al., 2005]. This could indicate a larger hominin on Flores at 1 ma, potentially Java H. erectus , who is the only known hominin around Indonesia at 1 ma [Morwood et al., 2003]. These stone tools could indicate that rapid dwarfism occurred between 1- 0.7 ma, when H. floresiensis fossils are first dated [Van den Bergh et al., 2016].

In a comparison between Liang Bua and Mata Menge scar dimensions on cores, the Mata Menge site yielded samples with much larger dimensions up to and over 71mm, in contrast to Liang Bua’s biggest scar dimension samples being under 50mm [Brumm et al., 2006]. This may show a decrease in flake size over time, although fossil evidence suggests the Mata Menge hominins had already dwarfed to a similar size of those found at Liang Bua [Brumm et al., 2016], and the largest sample at each site is shown in the ranges of 11-33mm [Brumm et al., 2006]. Acheulean handaxes in comparison, which were being produced around the world by 90 ka [Scott and Gibert, 2009], vary in size with some handaxes seeming inefficiently large in relation to body size [Leakey and Roe, 1994 Currie, 2016]. These handaxes are however often debated to be potentially ritualistic or used in acquiring mates [Kohn and Mithen, 1999], as Key and Lycett tested in their paper on flake size in relation to cutting effectiveness that there is a threshold in which too small a flake becomes inefficient. However, once beyond this threshold the relationship is not absolute between increased size and cutting efficiency [2014] suggesting bigger is not always better. Due to the relatively simplistic form of the tools on Flores (core and flake technology) it seems unlikely that they were being made for something other than functional use, attesting to the theory that Wolo Sege may represent a larger hominin species that could be the direct ancestor of H. floresiensis .

Archeological records for tool use in Indonesia are scarce, despite there being a strong fossil record of H. erectus in Java [Dubois, 1894 Dubois, 1937 Jacob, 1964 Sartono, 1972]. Recent studies have suggested alternative materials were being sourced for tool making like bamboo [West and Louys, 2007 Gorman, 1971] or shell tools [Joordens et al, 2015], although this research is very localised and is limited to one example of potential shell tool use so cannot serve as a basis of tool use throughout Indonesia. African populations of H. erectus however begin to produce a more advanced Acheulean technology as early as 1.7 ma [Diez-Martín, 2015]. The Acheulean technology is recognised for its spread across the world, but is missing from the archeological record in East Asia and Indonesia due to potential scarcity of raw material [Stone, 2006 Joordens et al, 2015]. Whilst stone tools have been found (Widianto et al, 2008), they are contentious and are still relatively few in comparison to other parts of the world. This lack of lithics in Indonesia prior to the discoveries on Flores in three separate localities can perhaps give better understanding as to the technological simplicity seen in the Flores lithics in comparison to the Acheulean tools around the Old World (Africa, Europe and Asia) at a similar time. The implications from the stone tools found on Flores suggest that H. floresiensis was a scavenger and was not actively hunting animals for food sources. Close analysis of the time-budget assessment by Dunbar shows the cost-effectiveness that meat consumption brought and the essentiality to the maintenance of large brain size [2014a 2014b]. However, with selective pressures of reducing body size and especially reducing the size of their costly brain it seems reasonable to assume meat consumption (which could involve dangerous scavenging techniques) was potentially reduced and was not relied upon for their daily diet. This also brings together the alternative pressures H. floresiensis may have faced, resulting in their large feet and toe bones displaying curvature. These features share similarities with Australopithecus [Junger et al., 2009] for at least the potential for partial arboreal locomotion and habitat.

The variation seen in H. erectus is so vast it has frequently been proposed that many of the fossils should be divided into several subspecies [Antón, 2003], but with the discovery of the Dmanisi’s fossils and their considerable variation despite being discovered within such close temporospatial proximity to each other [Lordkipanidze, 2013] has caused debate on variation limits within a species. This enhances the claim that H. floresiensis ’ more primitive features could be a result of an earlier variation of H. erectus (than represented by current Indonesia and Chinese H. erectus material) that retained some features seen in African early Homo . This is important for the hypothesis of insular dwarfism, as many critics have argued a more primitive hominid ancestor seems a likely candidate for ancestry for example, Australopithecus is more similar in stature and cranial capacity to H. floresiensis [Morwood et al, 2005 Argue et al, 2006]. This would potentially lessen the claim of insular dwarfism in this species. The argument for an earlier hominin species being directly ancestral to H. floresiensis is contentious mainly due to no evidence of earlier hominin dispersals Out of Africa prior to H. erectus . Aspects of the morphology of H. floresiensis are derived and place them in the Homo genus [Brown et al., 2004] making suitable inferences that ancestry is unlikely that of earlier hominins that is the Australopiths, this is notably from their derived molar morphology exhibiting a modern humans molar reduction patterning: M1>M2>M3 [Brown et al, 2009 Kaifu et al, 2015] unless H. floresiensis evolved these features independently on the Island.

Derived molar patterns seen in Homo sapiens are linked with selection pressures of a decreasing jaw size with less mastication demands and consumption of cooked/softer foods that are easier to consume without large molars. Whilst we see some evidence of controlled fire at Liang Bua with charred bone fragments [Morwood et al., 2004], this is an isolated case on Flores, with no evidence of this at Mata Menge. It is presumed due to the Oldowan style tools found, that H. floresiensis did not rely on meat consumption regularly in their diet, but had presumably a predominantly C4 plant diet, based on isotope data taken from S. f. florensis and sediments on Flores with changing climates. If meat and cooking were not essential in H. floresiensis ’ diet, or at least not until 70 ka when they are at Liang Bua, the selective pressure for this derived molar morphology is not likely to be related to diet on the island, but rather their diminutive size. However Australopithecines were relatively small at an estimated 145-152 cm [Olivier, 1976 McHenry, 1974] and still maintained these large molars due to their diet. From this, the derived molar morphology seems to indicate evidence for a later hominin being the direct ancestor to H. floresiensis .

Due to limited fossil evidence, not much is known on H. floresiensis ’ sexual dimorphism, but if we are to look at H. erectus ’ dimorphism as a stem ancestor, the fossil record points to a ‘marked… dramatic increase in body size especially in the female’ [McHenry, 1994 Plavcan, 2012] suggesting a probably similar dimorphism in H. floresiensis if they are direct descendants, as it is unlikely sexual dimorphism would increase alongside insular dwarfism if selection pressure was as high as it is assumed to be. In contrast to this, Bromham and Cardillo’s model on primates indicates greater and more rapid change in size in ‘taxa with more pronounced sexual dimorphism in head–body length’ [2007].

Whilst it is useful to apply ‘conceptual evolutionary frameworks’ from the animal kingdom, it must not be used solely as the bases for a theoretical concept [Bailey, 2009] examples of adaptations in modern humans can also give a better understanding to H. floresiensis ’ morphology. This is important when analysing potentially “primitive” features observed in H. floresiensis that may indicate a degree of specialisation. Just as H. erectus also displays the first signs (as the first known hominin to leave “Africa”) of cultural differences/adaptations in the lithic record but also variation in diet and morphology with cranial capacity ranging from 600- <1000 cc [Leakey et al., 1964 Gabunia et al., 2000 Lordkipanidze et al., 2013 Anton et al., 2016].

Human pygmy populations are examples of members within our own species adapting to their environment and could also help to explain H. floresiensis ’ morphology and life-history. Perry and Dominy note the pygmy phenotype has been traditionally observed in hunter gatherer communities in specific climates namely tropical rainforests [2009]. It has been proposed by many that pygmy peoples short stature and slight body weight is due to malnutrition during prepubescence/preadolescence [De Souza, 2006]. However, populations across the world experience nutritional stress whilst still maintaining average adult heights greater than rainforest pygmy populations, indicating their stature is not entirely down to limited food resources [Perry and Dominy, 2009]. Taken together, pygmy populations portray successful adaptations and a life history that has proved successful in several areas of the world (the phenotype for short stature confers increased mobility and foraging in rainforest/savannawoodland climates [Diamond, 1991]), which has been favoured by selection in multiple continents separately- with pygmy populations being closer related to populations within relative proximity than to other pygmies [Perry and Dominy, 2009]). Their success displays a good argument for H. floresiensis ’ rapid dwarfism and their adaptiveness to the changing environment on Flores [Puspaningrum, 2016].

Classifications of pygmy height are generally referred to as below 150-160 cm for adult males [Perry and Dominy, 2009] compared with a worldwide population (2,503 ethnographic populations) of average adult male height at 163.9 cm [Migliano et al., 2007], displaying much less reduction than seen in H. floresiensis with H. erectus . Unlike pygmy populations that occupy rainforest environments around the world, H. floresiensis shows clear speciation from any other known hominin, and could not be defined as a pygmy H. erectus . The post-crania phenotypic differences are the best evidence for individual speciation, which show a degree of what can be assumed as either retaining primitive features of their ancestors (whilst also displaying derived features not seen elsewhere in the hominin fossil record) or adaptations to their environment. The slim body and long limbs that are distinguishing features in H. erectus presumed to be adapted for endurance running [Bramble and Lieberman, 2004] seem counterintuitive in the rainforest environment of Flores where small stature is selected for [Perry and Dominy, 2009].

It is important to also understand and briefly interpret the arguments against the theory of insular dwarfism for H. floresiensis . Whilst several disputes on H. floresiensis have occurred, the most difficult to explain is LB1’s crania ( H. floresiensis type specimen) showing what has been interpreted to be an array of pathologies [Henneberg and Thorne, 2004 Weber et al., 2005], with the asymmetrical cranium shape to rotated premolars found only in H. floresiensis and specific populations on Flores today [Jacob et al., 2006]. Many of these pathologies could indicate much about the context of the hominins’ life, however limited fossil remains impede the full picture of this species that survived for over 600 ka. Whilst pathologies on LB1 seem a valid claim, it is not enough to expel the insular dwarfism hypothesis out of possibility.

Taking examples from insular dwarfism in the animal kingdom gives good insight into how an environment can selectively pressure its inhabitants. The benefits of dwarfism for large land mammals has been evidenced, but most cases usually result in a subspecies of their mainland relatives. H. floresiensis shows clear speciation in their large feet and primitive wrists (distinguished as closer to morphology of extant apes and early hominins), whilst also possessing derived features that are closer to H. erectus . We know H. erectus varied considerably in cranial capacity and morphology and whilst no evidence of a more primitive Java hominin fossil has been found, it could help explain some of the features of H. floresiensis . What continues to remain elusive is how these hominins arrived on Flores. As we now have an additional case of diminutive hominins on the island of Luzon [Détroit et al., 2019], it must be considered that these hominins were potentially capable of seafaring. As the literature has illustrated, the evidence from H. floresiensis ’ crania, the lack of other hominins present around Indonesia at the time of its appearance and the known examples of insular dwarfism occurring on Flores is all suggestive of H. erectus being the direct ancestor to H. floresiensis and that a rapid decrease in size and particular morphological changes were essential for survival on the island.

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