Friday, January 11, 2013

More Hobbit Fossils Confirm Existence Of Species

Newly reported research on  Homo floresiensis confirms that these Hominin skeletal remains from the Indonesian island of Flores really do represent a distinct species or subspecies of hominins, rather than diseased individual Homo sapiens.  Basically, the new research confirms the prior research in Flores.

The Hobbits Were A Distinct Species Of Small Hominins.

According to lead author Caley Orr:
The tiny people from Flores were not simply diseased modern humans. . .  The new species of human stood approximately 3' 6" tall, giving it its nickname "The Hobbit" . . . [T]hey walked on two legs, had small canine teeth, and lived what appears to have been an iconic "cave man'" lifestyle. Stone tools and evidence of fire use were found in the cave, along with the remains of butchered animals, such as Stegodon (an extinct elephant relative), indicating that meat was a part of diet.
But, there were differences from modern human as well:
The Hobbits had arms that were longer than their legs, giving them a slightly more ape-like structure. Their skulls had no bony chins, so their faces had more of an oval shape. Their forehead was sloping. The inferred brain size was tiny, putting them in the IQ range of chimpanzees.  . . . the feet were also long relative to the legs.
According to anthropologist Tracy Kivell:
These fossils provide further, clear evidence that H. floresiensis is in no way a pathological modern human, or that its primitive morphology is related simply to its small body size. Instead, it is clearly its own, unique and very intriguing species. . . .  
What is particularly interesting is that H. floresiensis is associated with such a long, well-documented history of stone tools. (Its primitive hand and wrist were) still apparently capable of making and using stone tools, suggesting that H. floresiensis solved the morphological and manipulative demands of tool-making and tool-use in a different way than Neanderthals and ourselves.
Is Denisovan Admixture In Modern Humans Really Hobbit Admixture?

So, where does Homo floresiensis fit in the hominin evolutionary tree?
The Hobbit's wrist looked like that of early human relatives, such as Australopithecus, but the key ancestral candidate now is Homo erectus, "Upright Man." It is possible that a population of H. erectus became stranded on the Indonesian island and dwarfed there over time. Orr said that "sometimes happens to larger animals that adapt to small island environments." A problem, however, is that H. erectus is somewhat more modern looking than the Hobbit, so researchers are still seeking more clues.
And, what role did they play in the prehistory of modern humans?
Another question concerns whether or not the Hobbits ever mated with modern humans. . . . So far, however, conditions have not been right to extract DNA from H. floresiensis bones.
The Geography Of Flores Fits The Modern Population Genetic Boundaries Of Denisovan Admixture



The island of Flores is very close to the Wallace line (the biogeographic barrier between areas once connected by land to mainland Asia and those that were not for a hundred million years or so). This is also the point at which modern humans whose genomes have archaic admixture corresponding the ancient DNA from the Denisova cave in Siberia (basically Aboriginal Australians and Papuans and peoples admixed with those populations).


Hobbits And Modern Humans Co-Existed For 32,000 Years

Homo floresiensis related artifacts start to appear around 95,000 years ago on the island of Flores.  Modern humans reached the island of Flores around 45,000 years ago.

There is evidence that Homo sapiens and Homo floresiensis probably co-existed on the island of Flores for many thousands of years, and as recently as 17,000 years ago by conservative estimates, and more likely until at least until 13,000 year ago.  This is roughly 32,000 years after the founding populations of Australia and Papua New Guinea's indigenous populations cross through Flores en route to their final destinations.

In contrast, periods of co-existence between Neanderthals and modern human populations in geographic regions that small, or between modern human hunter-gatherer populations and first farmer populations in geographic regions that small, where we have accurate archaeological evidence, appear to have typically lasted no more than 1,000 years in any one place.  There are no archaeological examples of mixed Neanderthal-modern human communities.

Neanderthals and modern human hunter-gatherers co-existed in Europe for about 21,000 years, and in the Levant for perhaps 25,000 years or so, but for the most part, they did not exist so close to each other in any one place for anything close to that long of a time period.  Europe is a much bigger place than the island of Flores.

Of coure, early divergence of Australian and Papuan populations (the Philippine Negrito group called the Mamanwa people also probably had common origins with these two population and diverged around the same time) strongly suggests that admixture that survived into populations in existence today happened during the first few thousand years (or less) of that co-existence.  But, the long period of co-existence points to a stable and cooperative form of co-existence, something that local legends on the island of Flores (discussed below) also support.

There Are Plausible Reasons For Modern Human Interactions With Hobbits To Be More Peaceful Than Those With Homo Erectus.

One plausible possibility is that a stable symbiotic relationship developed between Homo floresiensis and modern humans, but not between Homo erectus and modern humans, because the small and childlike Homo floresiensis seemed less threatening to modern humans.

Also, the difficulty involved in crossing the straight to reach the island of Flores may have kept the initial modern human population of the island whose first contact experience set the tone for future interactions small enough that it did not overwhelm the Hobbits.  In contrast, when archaic hominins on the mainland encountered wandering modern human tribes, the modern humans may have so dramatically outnumbered the archaic hominins that defeating them or routing them from their traditional homes may have been so easy that there was no incentive to develop interacts that didn't lead to archaic hominin extinction.

If the modern human population that admixed with  Homo floresiensis was small, this would also make it possible for a very small number of admixture events to account for the inferred nearly 8% initial modern human-Denisovan admixture level that modern population genetic studies suggest was present via founder effects.

There Are Few Other Plausible Sources Of Denisovan Admixture In Modern Humans

In contrast, there is no archaeological or population genetic evidence for prolonged period of co-existence between Homo sapiens and Homo erectus proper (one of the type fossils for which is Java man, just a few channel crossings over in Indonesia).  Tropical conditions in much of the region and the minimal research funds available for archaeology in Asia until very recently could also explain this gap in the fossil record. 

The absence of archaic non-Neanderthal admixture in existing mainland Asian populations, also points to limited or non-existence admixture between ordinary Homo erectus and modern humans although the population genetic evidence poses very different preservation concerns.  In the case of population genetics the strongest possibility to account for is the possibility that subsequent waves of modern humans may have entirely replaced the earlier waves of modern humans in Asia that could have admixed with Homo erectus. 

There is also no substantial evidence that there was ever a Neanderthal presence anywhere significantly to the east of India, which is notable given how well the lithic tool culture of Neanderthals has been studied and how well lithic tools can be preserved even when skeletal remains are not preserved.  It could be that bamboo or some other perishable tool materials were more attractive in Southeast Asia than stone and that this disrupted the culturally transmission of Neanderthal lithic industries, but this seems fairly implausible to me given that earlier archaic lithic traditions found in Africa were transmitted to Southeast Asia around 2 million years ago when Homo erectus arrived in Asia.

Thus, a lack of other good alternative candidates is another reason to suspect that Denisovan admixture in the modern human genome is really Homo floresiensis admixture.

Bottom Line: Hobbits May Be Among The Ancestors Of People Alive Today

The bottom line is that a variety of factors make Homo floresiensis a particularly attractive potential source for so called "Denisovan" admixture observed in modern humans. Indeed, I would argue that they are the most likely source of this archaic admixture in modern humans.

In the most likely hypothesis, Homo floresiensis were a pygmy derivative of Homo erectus, and the Denisovan samples of ancient DNA from Siberia look like a source of admixture because they are also derived, at least in substantial part, from a common Homo erectus ancestor.

Were Hobbits The Last Archaic Hominins On Earth?

Probably as a result of their geographic isolation and possibly also as a result of a stable symbiotic relationship with co-existing modern humans on Flores, Hobbits may have been one of the last archaic hominin species to go extinct. 

A conservative estimate suggests that they went extinct 17,000 years ago.   This is around the time of the last glacial maximum and would suggest that an influx of a new wave of modern humans at this time could have caused their extinction.

But, there is good evidence that they persisted as recently as 12,000 to 13,000 years ago.   See Morwood, M. J.; Soejono, R. P., et al.,"Archaeology and age of a new hominin from Flores in eastern Indonesia". Nature 431 (7012): 1087–1091 (October 27, 2004) and Morwood, M. J.; Brown, P., et al.,"Further evidence for small-bodied hominins from the Late Pleistocene of Flores, Indonesia". Nature 437 (7061): 1012–1017 (October 13, 2005). As Wikipedia explains:
Local geology suggests that a volcanic eruption on Flores approximately 12,000 years ago was responsible for the demise of H. floresiensis, along with other local fauna, including the elephant Stegodon.   
The estimated date of their extinction 12,000 years ago is about 12,000 years after the most recent known Neanderthal remains and about 80,000 years after the most recent reliably dated and typed Homo erectus remains. It is fairly close in time to a couple of inferred dates of admixture between archaic hominins and Paleo-African populations (i.e. modern human pygmies and Khoisan populations in South Africa) based on population genetic analysis for which there are no fossil remains, in part, due to poor preservation conditions in tropical Africa.

Did Homo floresiensis survive into the modern era? 

There is also a legitimate case to be made for a much more recent demise of H. floresiensis,
Gregory Forth hypothesized that H. floresiensis may have survived longer in other parts of Flores to become the source of the Ebu Gogo stories told among the Nage people of Flores. The Ebu Gogo are said to have been small, hairy, language-poor cave dwellers on the scale of this species. Believed to be present at the time of the arrival of the first Portuguese ships during the 16th century, these creatures are claimed to have existed as recently as the late 19th century.  Gerd van den Bergh, a paleontologist working with the fossils, reported hearing of the Ebu Gogo a decade before the fossil discovery.
At least one reputable linguist has conjectured, but cannot prove, that the linguistic structure of one of the main languages spoken in Flores reflects the effects of contact with Homo floresiensis, who may have served as servants of early modern humans in Flores. This makes some sense. It is hard to see how to hominin species could manage to co-exist in a geographic niche as small as the island of Flores for 32,000 without either causing the other to go extinct, if these communities did not live in a symbiotic, cooperative relationship with each other.

A linguistic connection, if there is one, suggests strongly that some population of Homo floresiensis survived long after the volcanic erruption 12,000 years ago and lends credence to the legends that claim that they actually went extinct somewhere in the last five hundred years, as a time depth of 12,000 years would be too far in the past to leave the kind of linguistic trace suggested.

Does the species survive today?
On the island of Sumatra, there are reports of a 1–1.5 m (3 ft 3 in–4 ft 10 in) tall humanoid, the Orang Pendek which might be related to H. floresiensis. Henry Gee, senior editor at Nature magazine, speculates that species like H. floresiensis might still exist in the unexplored tropical forest of Indonesia.
The evidence cited to the effect that some Orang Pendek may be a non-extinct species on Sumatra, while not bringing their existence to the level of an incontrovertable scientifically discovered fact, is not insubstantial.
[The Orang Pendek] has allegedly been seen and documented for at least one hundred years by forest tribes, local villagers, Dutch colonists, and Western scientists and travelers. Consensus among witnesses is that the animal is a ground-dwelling, bipedal primate that is covered in short fur and stands between 80 and 150 cm (30 and 60 in) tall. . . . Hundreds of locals claim to have either seen the animal personally or can relate stories of others who have.
These observations are tied to a particular location:
While Orang Pendek or similar animals have historically been reported throughout Sumatra and Southeast Asia, recent sightings have occurred largely within the Kerinci regency of central Sumatra and especially within the borders of Taman Nasional Kerinci Seblat (Kerinci Seblat National Park) (TNKS).[1][2][8] The park, 2° south of the equator, is located within the Bukit Barisan mountain range and features some of the most remote primary rainforest in the world. Habitat types within the park include lowland dipterocarp rainforest, montane forests, and volcanic alpine formations on Mt. Kerinci, the second highest peak in Indonesia.[8] Because of its inaccessibility, the park has been largely spared from the rampant logging occurring throughout Sumatra and provides one of the last homes for the endangered Sumatran Tiger.
If the Orang Pendek really does still exist, or did until recently, and DNA samples and skeletal remains could be obtained, this would be a truly extraordinary discovery.  Certainly, the search deserves more resources than the one year National Geographic study funded effort in 2009 by a lonely couple of investigators.

This article was updated with links and some additional material on January 15, 2013.

8 comments:

terryt said...

I have always had difficulty accepting that the 'Hobbits' were diseased individual Homo sapiens so this paper is a real pleasure.

"In the most likely hypothesis, Homo floresiensis were a pygmy derivative of Homo erectus"

That's what I've always accepted.

"It is possible that a population of H. erectus became stranded on the Indonesian island and dwarfed there over time. Orr said that 'sometimes happens to larger animals that adapt to small island environments'".

That explanation has always made sense to me.

"and the Denisovan samples of ancient DNA from Siberia look like a source of admixture because they are also derived, at least in substantial part, from a common Homo erectus ancestor".

I'm yet to be convinced of that.

"Thus, a lack of other good alternative candidates is another reason to suspect that Denisovan admixture in the modern human genome is really Homo floresiensis admixture".

I think the obvious candidate is the most likely one: The Denisova population from Altai. Why look elsewhere?

"It could be that bamboo or some other perishable tool materials were more attractive in Southeast Asia than stone and that this disrupted the culturally transmission of Neanderthal lithic industries, but this seems fairly implausible to me"

Agreed.

"There is also no substantial evidence that there was ever a Neanderthal presence anywhere significantly to the east of India, which is notable given how well the lithic tool culture of Neanderthals has been studied and how well lithic tools can be preserved even when skeletal remains are not preserved".

The difficulties of movement between India and SE Asia have been consistently under-rated. Most historical human movement has been from SE Asia to India except for a sea-born Indian trade in very recent times. In spits of what Maju claims a Central Asian route through semi-forested grassland is much more likely, especially when we consider that humans of some sort have lived far to the north almost from the moment that H. erectus emerged from Africa (if indeed it did so):

"A problem, however, is that H. erectus is somewhat more modern looking than the Hobbit, so researchers are still seeking more clues".

Yes. A problem. The same with the Tblisi H. erectus, if they are indeed H. erectus. To me it seems likely that some Australopithecus was first out of Africa, not fully-evolved H. erectus. H. erectus actually formed in Asia, then some moved back into Africa, where H. ergaster evolved, or had already evolved. To me it makes no sense that human populations have always moved to some new region where they have remained isolated until replaced by later migrations. To me it makes sense that evolution, including human evolution, is a dynamic process, not static.

DDeden said...

I like your conjectures regarding Denisovans, Papuans and Hobbits. I hadn't thought of that.

My view: The Flores Hobbits were simply among the first OOA2 Hss groups, (sometime between 200ka and 50ka), they were part of the pygmy diaspora (the Mbuti side, not the Mbara) they got isolated on Flores and adopted drastically different lifestyles due to the radically different ecosystem on Flores, resulting in drastically different bone morphologies.

terryt said...

"they were part of the pygmy diaspora (the Mbuti side, not the Mbara)"

I think they are much closer to H. erectus than are the Mbuti Pygmies though. In fact it seems likely that the Hobbits are more distant from 'modern' humans than are H. erectus, so that makes any connection to african Pygmies even less likely.

velvetgunther said...

If there indeed was an admixture, I'd wonder which direction it took. Considering the discrepancy in size, would it even have been possible for a 'hobbit' female to give birth to a half modern human baby? The other way round is, well, quite kinky to think of...

DDeden said...

TerryT, I'm willing to accept that as plausible. However, my research shows that both pygmy branches crossed the Punt (bridge to Yemen)and the shallowed Persian Gulf, the Mbuti towards the Narmada River (eg. Tibet, Cambodia, Flores) while the Mbak/ra followed the coast south (eg. Sri lanka, Andamans, Queensland, Tasmania).


andrew said...

"See this map from the 2011 paper by Reich and Stoneking. Dravidians (who have a lot of Veddoid ancestry) had the least Denisovan ancestry of all the populations they studied (none of statistical significance). The map shows that there's no statistically significant Denisovan ancestry as far east as Sumatra and Borneo, and that the furthest west that statistically significant Denisovan ancestry is found is Flores. No populations from Java, Bali, Lombok, or Sumbawa were tested. Now this dividing region is very interesting, because Java is where all of the Southeast Asian Homo erectus fossils were found, and Flores is where Homo floresiensis was found. I have to believe that there was some kind of relationship between Denisovans and erectus and/or floresiensis."

From here.

DDeden said...

I'd expect that (per Andrew's map) AU1 & AU2 were not Aust. pygmy samples, that Aust. pygmies would have almost no Denisovan and Neanderthal. I note with interest that Flores does have some Denisovan which I think was a later group perhaps from Cambodia, containing Mbuti & Densiovan genes (based on Bodha/Bidaya).

terryt said...

"I have to believe that there was some kind of relationship between Denisovans and erectus and/or floresiensis".

And, of course, the population in the Altai.

"Dravidians (who have a lot of Veddoid ancestry) had the least Denisovan ancestry of all the populations they studied (none of statistical significance)".

Which to me is the most fascinating aspect of all.

"I'd expect that (per Andrew's map) AU1 & AU2 were not Aust. pygmy samples"

Australian Pygmies? I ain't never heard of that.