[Taxacom] "Hobbit" research

[John Grehan]

It was interesting to see The Scientist.com article about new articles
in nature on the hobbit foot. Apparently the hobbit foot does not
conform to the Homo erectus foot, but shows greater similarities with
other fossil taxa, with Homo habilis being cited in particular.
Ironically, the original claim for Homo erectus was never
phylogenetically substantiated in the first place, and the 'Homo'
designation was originally a propaganda device. I've still yet to see
anything substantial supporting the 'Homo' placement for the hobbit. But
I'll dig into the literature a bit more.

Also interesting is the reference to the hobbit as a hominin. This term
is only applicable if one supports a human-chimp clade to the exclusion
of orangutans. In terms of clarity I would prefer to see Hominidae apply
to all large bodied hominoids, or just to humans and those fossil taxa
more closely related to humans than the nearest living great ape
relative - whatever that is. For the purposes of the forthcoming
human-orangutan analysis, hominid is restricted to the latter.

John Grehan  

News:
Hobbit origins from head to toePosted by Bob Grant
[Entry posted at 6th May 2009 06:00 PM GMT]
View comment(1) | Comment on this news story   
 
Ever since 2003, when researchers found the skeletal remains of a
diminutive, human-like creature--dubbed the Hobbit--on an island in
Indonesia, a debate has raged over whether the find represents a new
species or a just deformed population of an existing species. Two papers
appearing in Nature today--one addressing the shape of its feet and the
other the size of its head--confirm that Homo floresiensis is in fact a
separate species, but each posits slightly different evolutionary
origins for this latest addition to the human family tree. 

"Both of these papers show things that could not have evolved or been a
plastic response within our own species," George Washington University
paleoanthropologist Bernard Wood told The Scientist. Wood, who was not
involved with either study, added that the papers raise important
questions regarding the evolutionary origins of H. floresiensis that
only further research can answer. 

H. floresiensis was a hominin--the taxonomic group that includes genus
Homo, extant chimp species, and their ancestors--that inhabited the
island of Flores more than 10,000 years ago and likely stood about a
meter tall. The current debate over the Hobbit's evolutionary origins
centers around whether or not the species could have evolved its
peculiar body proportions from a Homo erectus ancestor or if some more
primitive human ancestor was necessary to explain its mixture of modern
and primitive features. Researchers had previously taken the lack of a
mechanistic explanation for the relative smallness of H. floresiensis's
brain as support for the idea that the find represented a deformed,
extant species. 

Such a mechanistic explanation is provided by the first paper, from
mammalian paleontologists Eleanor Weston and Adrian Lister of London's
Natural History Museum. Their study suggests that H. floresiensis did
indeed result from the dwarfing of a population of H. erectus
individuals. The two researchers studied the cranial morphology of two
recently-extinct Malagasy hippopotamus species and presented a model
that overturns the notion that dwarf mammals, stunted by evolutionary
pressures on confined island habitats, cannot develop brains as
proportionately small as those seen in H. floresiensis. (Hobbits had a
417 cm2 brain in a body that was about 30 kg.) 

The fact that the two pygmy hippopotamus species experienced dwarfing
that left them with significantly smaller brains than their normal-sized
ancestors on the mainland shows these morphological changes could have
occurred in some Homo erectus specimens to result in the brain-body size
ratio seen in H. floresiensis. 

"It's possible that humans have been exposed to the same evolutionary
pressures that have caused these changes in other mammals," Weston told
The Scientist. "At the end of the day this doesn't prove that Homo
floresiensis is a dwarf Homo erectus. It just suggests that it's a
possibility." She added that Homo habilis could also be the Hobbit's
ancestor with her island dwarfing model accounting for the reduced brain
size. 

In the other Nature paper, William Jungers, a paleoanthropologist at
Stony Brook University in New York, and his coauthors compared the
Hobbit foot to the few existing feet in the fossil record. "You just
don't see complete feet until you get into Neanderthal," Jungers told
The Scientist. "The fossil record of feet is surprisingly meager." 

The group found that its proportions were more similar to feet found in
human ancestors that roamed Africa more than three million years ago
than they are to the feet of more modern hominin species, such as Homo
erectus. "Homo erectus has a modern foot in comparison to Homo
floresiensis," Jungers said. Fossil footprints recently discovered in
Africa suggest that H. erectus evolved modern foot architecture some 1.5
million years ago. 

Specifically, the Hobbit had long feet compared to the length of its leg
bones, according to Jungers, and lacked arches; two decidedly primitive
Homo features. If H. floresiensis was in fact a dwarfed H. erectus, the
species would have had to amass primitive features after its ancestor
had already evolved more modern skeletal characteristics. "It's asking a
lot for evolution to backtrack like that," Jungers said. "Is it
possible? I guess, but there's no precedent." 

Instead, Jungers said he believes that H. floresiensis's ancestor could
have been a species--possibly H. habilis--that left Africa before H.
erectus did around 2 million years ago. "There were probably other
dispersal events in human history that we don't have a handle on,"
Jungers noted. 

Wood agreed. "I think [H. floresiensis's ancestor] is probably likely to
be an early Homo taxon other than Homo erectus," he told The Scientist.
Which species that might be isn't clear, he said; the Hobbit's ancestor
could have been an ancient human species that has yet to be discovered
or classified. 

Richard Potts, a Smithsonian Institution paleoanthropologist not
involved with either study, added that Weston's findings indicate that
island dwarfing, a poorly understood phenomenon, could yield yet more
surprises. "Junger's argument does not cast away the idea that [H.
floresiensis's ancestor] could have been an early Homo erectus," he told
The Scientist. "There are some unexpected things that occur with island
dwarfing. It opens up the possibility that there could be ways that the
foot or other body proportions could back track." 

> -----Original Message-----
> From: Kenneth Kinman [mailto:kennethkinman at webtv.net]
> Sent: Wednesday, May 06, 2009 9:14 PM
> To: lynn at afriherp.org
> Cc: John Grehan
> Subject: Re: "Hobbit" research
> 
> Hi Lynn,
>       Thanks for the weblink.  The new paper on the hobbit's foot is
> particularly interesting.  Too bad that we don't have a foot of Homo
> erectus georgicus, Homo erectus ergaster, or Homo habilis for
> comparison.  However, it does add weight to the argument that the
hobbit
> was probably not a direct descendant of Homo erectus erectus.
>           --------Ken
> -------------------------------------------------------