Feet Of Homo Floresiensis Were Primitive But Not Pathological

[Knight-Dragon]

http://www.sciencedaily.com/releases/2009/05/090506144307.htm

ScienceDaily (May 6, 2009) — A detailed analysis of the feet of Homo floresiensis—the miniature hominins who lived on a remote island in eastern Indonesia until 18,000 years ago—may help settle a question hotly debated among paleontologists: how similar was this population to modern humans?

A new research paper, featured on the cover of the May 7 issue of Nature, may answer this question. While the so-called "hobbits" walked on two legs, several features of their feet were so primitive that their gait was not efficient.

"The hobbits were bipedal, but they walked in a different way from modern humans," explains William Harcourt-Smith, a Research Scientist in the Division of Paleontology at the American Museum of Natural History and an author on the paper. "Their feet have a combination of human-like and more primitive early hominin traits, some of which are more akin to those in Lucy." Lucy is an early bipedal but small-brained hominin, or australopithecine, that lived in Africa 3.2 million years ago.

The "hobbits," excavated from Liang Bua Cave on the island of Flores, were first described in 2004. Known specimens range in age from 90,000 to 18,000 years old, making them contemporaneous with modern humans. This, in combination with the unusually small stature and brain size of H. floresiensis, led to considerable debate among researchers and in the press. Some consider the population a separate species, while others have assessed the fossils as pathological modern humans. But a number of recent analyses of the skull, face, and wrist have found many unusually primitive features among the "hobbits" that are more similar to chimpanzees and Australopithecus, suggesting that the Flores inhabitants represent a remnant population of early hominins.

The anatomy of the foot described in the new paper might finally answer the pathological modern vs. primitive population question. Although the foot is characteristic of a biped—being stiff and having no opposable big toe—many other traits fall outside of the range for modern humans. The H. floresiensis foot is very long in proportion to the lower limb and considerably more than half the length of the thighbone; modern human feet are relatively shorter at about half of the femur's length. The stubby big toe of the hobbits is another primitive, chimp-like trait. But the pivotal clue comes from the navicular bone, an important tarsal bone that helps form the arch in a modern human foot. The "hobbit" navicular bone is more akin to that found in great apes, which means that these hominins lacked an arch and were not efficient long-term runners.

"Arches are the hallmark of a modern human foot," explains Harcourt-Smith. "This is another strong piece of the evidence that the "hobbit" was not like us."

Researchers also assessed the pathology hypothesis by comparing "hobbit" feet to those of typical modern humans and pathological modern specimens such as pituitary dwarfs. While the pathological specimens fell well within the range of modern humans, the "hobbits" did not. This suggests that H. floresiensis was an unusual, isolated population of early hominins.

"The fossil record continues to surprise us," says William Jungers, Chairman of the Department of Anatomical Sciences at Stony Brook University Medical Center, and an author on the study. "H. floresiensis is either an island-dwarfed descendant of H. erectus that not only underwent body-size reduction but also extensive evolutionary reversals, or, as our analysis suggests, it represents a new species full of primitive retentions from an ancestor that dispersed out of Africa much earlier than anyone would have predicted. Either way, the implications for human evolution are profound."

In addition to Jungers and Harcourt-Smith, authors of the research paper include Roshna Wunderlich, James Madison University; Matthew Tocheri, National Museum of Natural History (Smithsonian Institution); Susan Larson, Stony Brook Medical Center; Thomas Sutikna and Rhokus Awe Due, National Research and Development Centre for Archaeology in Jakarta, Indonesia; and Mike Morwood, University of Wollongong in Australia. Research was funded by grants form the Australian Research Council, the National Geographic Society, the Wenner-Gren Foundation for Anthropological Research, the Wellcome Trust, and the Leakey Foundation.

 

[Eran of Arcadia]

That would at least help explain where they fit in the hominid line.

 

[Knight-Dragon]

On a related note...

http://www.sciencedaily.com/releases/2009/05/090507185535.htm

Small Brain Of Dwarf 'Hobbit' Explained By Hippo's Island Life

ScienceDaily (May 8, 2009) — Ancient Madagascan hippos have shed light on the origins of the small brain of the 1-metre-tall human, known as the hobbit, scientists at the Natural History Museum report in the journal Nature May 7.

By examining the skulls of extinct Madagascan hippos, Museum scientists discovered that dwarfed mammals on islands evolved much smaller brains in relation to their body size.

So Homo floresiensis may have had a tiny brain because it lived on an island. This is something which has been at the heart of the debate of the Hobbit’s origins, whose remains were uncovered on the Indonesian island of Flores in 2003.

The team suggests that the hobbit became a dwarf after its Homo erectus ancestor became isolated on the large island of Madagascar many years ago.

‘The discovery of a small fossil human from the island of Flores with normal facial proportions but a brain the size of chimpanzee has baffled scientists,’ explained Natural History Museum palaeontologist, Dr Eleanor Weston, who led the research.

‘It could be that its skull is that of a dwarfed mammal living on an island. Looking at pygmy hippos in Madagascar, which possess exceptionally small brains for their size, suggests that the ‘hobbit’ was a dwarf resulting from its H. erectus ancestors being isolated on the island in the past.’

Analysing hippos

Madagascar has many diverse habitats and in the past, has been the home to at least 3 species of hippo.

The team studied species of extinct Madagascan hippos and their mainland ancestor, the large common hippopotamus.

One of the specimens used, from the Museum’s mammal collection, was a nearly 3000-year-old dwarf hippo skull belonging to the extinct Hippopotamus madagascariensis.

Brain calculations

Hippo brain-body scaling trends were calculated from the relationship of brain to skull size.

‘We found that the brain sizes of extinct dwarf hippos were still up to 30% smaller than you would expect by scaling down their mainland African ancestor to the dwarf’s body size’ explains Dr Weston.

‘If the hippo model is applied to a typical H. erectus ancestor the resulting brain capacity is comparable to that of H. floresiensis.’

The brain of Homo floresiensis is the smallest yet known for any hominid, at around 400 mL.

A first for brain size

Although the phenomenon of dwarfism on islands is well recognised in large mammals, an accompanying reduction in brain size, as Dr Weston and Museum palaeontologist Professor Adrian Lister found, has never been clearly demonstrated before.

Energy use of brain

It may be advantageous to the survival of animals that become isolated on islands with unique environments, not only to become dwarfs, but also to reduce the size of their brain.

‘The brain is a costly organ that uses a lot of energy,’ says Dr Weston. ‘Whatever the explanation for the tiny brain of floresiensis relative to its body size, it’s likely that the fact that it lived on an island played a significant part in its evolution,’ concludes Dr Weston.

 

[JonathanStrange]

I recall reading - before H. Floresiensis' discovery - Evolution by Stephen Baxter, a scifi book that eventually had in the far distance future a primitive dwarf human species and the book made more real to me the idea that evolution doesn't have a goal or progression as we might define it. If a trait doesn't help for survival, it may eventually disappear: if intelligence beyond a certain level didn't help, the future humanlike inhabitants gradually lost it.

 

[El_Machinae]

This story is one of the more fascinating ones to be revealed recently. I mean, the implications are just stunning. Their presence & size on that island is an amazing mystery, their ancestry is an amazing mystery, and their evolution has multiple hypotheses, each with different implications.

We've seen other species lose brain size over generations, but I've never seen a hominid lose brain size due to islandisation. And the fact that they went extinct so recently, after (dare I say it?) "devolving" is just too cool.

NPR Science Friday did a much longer lay-analysis of this set of results. I very much recommend the audio article, because they really explained things well. Nature's podcast dealt with this too, in a bit more detail.

This is my favourite story of the year, I think.

 

[Narz]

Just out of pure curiosity. Would it be theoretically possible to clone one of these little guys &/or other extinct hominids or is there not enough (or intact enough) DNA to do so?

 

[Agent327]

That's a weird thought, though.

The hobbits were bipedal, but they walked in a different way from modern humans," explains William Harcourt-Smith, a Research Scientist in the Division of Paleontology at the American Museum of Natural History and an author on the paper. "Their feet have a combination of human-like and more primitive early hominin traits, some of which are more akin to those in Lucy." Lucy is an early bipedal but small-brained hominin, or australopithecine, that lived in Africa 3.2 million years ago.

This story is one of the more fascinating ones to be revealed recently. I mean, the implications are just stunning. Their presence & size on that island is an amazing mystery, their ancestry is an amazing mystery, and their evolution has multiple hypotheses, each with different implications.

We've seen other species lose brain size over generations, but I've never seen a hominid lose brain size due to islandisation. And the fact that they went extinct so recently, after (dare I say it?) "devolving" is just too cool.

NPR Science Friday did a much longer lay-analysis of this set of results. I very much recommend the audio article, because they really explained things well. Nature's podcast dealt with this too, in a bit more detail.

This is my favourite story of the year, I think.

Quite interesting, indeed.

 

[El_Machinae]

There's no DNA. These bones are a much rarer find, because the island is not ammenable to preserving bones. We find preserved mammoths because they're frozen in the tundra. We have Neanderthal DNA because Neanderthal went many, many places and so left a lot of skeletons.

These guys don't get frozen or buried deeply, so there's not as many bones.

 

[Simple Simon]

even having DNA does not mean you can just go ahead and clone. You need DNA from a cell that has undamaged complete DNA of the organism in an unaltered state. Also, you need the correct epigenetics.

 

[El_Machinae]

We can splice the DNA together from multiple samples, so you don't need a complete cell.
Epigenetic programming can probably be done by the host denucleated egg. If we clone mammoth, that's what probably will be done.

Though I don't think it would be moral to clone this species, since they're probably persons.

 

[Simple Simon]

We can splice the DNA together from multiple samples, so you don't need a complete cell.
Epigenetic programming can probably be done by the host denucleated egg. If we clone mammoth, that's what probably will be done.

We can try. But it is a lot more work, and assumes that we get the FULL DNA in the first place. If you lack a few fragments that can (but need not) be a real headache.