The Hobbit's bite gets a stress test
Stone tools may have allowed Homo floresiensis to eat their meals with
less chewing effort than earlier hominins.

Date:
August 23, 2021
Source:
Duke University
Summary:
If you've ever suffered from a sore jaw that popped or clicked
when you chewed gum or crunched hard foods, you may be able to
blame it on your extinct ancestors. That's according to a recent
study of the chewing mechanics of an ancient human relative called
Homo floresiensis, which inhabited the Indonesian island of Flores
before our species arrived there some 50,000 years ago.



FULL STORY ==========================================================================
If you've ever suffered from a sore jaw that popped or clicked when you
chewed gum or crunched hard foods, you may be able to blame it on your
extinct ancestors.


========================================================================== That's according to a Duke University-led study of the chewing mechanics
of an ancient human relative called Homo floresiensis, which inhabited
the Indonesian island of Flores before our species arrived there some
50,000 years ago.

Not much more than three feet tall, the hominin's diminutive size earned
it the nickname "the Hobbit," after the characters in J.R.R. Tolkien's
"The Lord of the Rings." For the new study, which was published Aug. 13
in the journal Interface Focus, the researchers wanted to understand
how the Hobbit's skull behaved while it ate its food.

However, thousands of years of fossilization had left its skull -- the
only one that has been found so far -- damaged and misshapen. Before
the researchers could test it out, they had to restore it as close to
its original shape as possible. Collaborators at Italy's University
of Bologna created a 3D virtual model, built from X-ray CT scans,
digitally filling in the missing pieces to reconstruct what the skull
of Homo floresiensis might have looked like when it roamed the island
some 100,000 to 60,000 years ago.

From that, they used computer simulations and a technique called finite
element analysis to give the virtual skull characteristics that mimic the
real thing, such as the stiffness of the bones and the pulling action of
the muscles. Then they had the virtual skull chomp down with its back
teeth -- premolars and molars -- and analyzed the forces at work with
each bite, essentially subjecting it to a digital crash test.

The researchers mapped the strains within their digital model of the
Hobbit's facial bones during biting, comparing the results to similar simulations for earlier human relatives called australopiths that lived
some two to three million years ago in Africa, along with chimpanzees
and humans living today.



==========================================================================
The team determined that the Hobbit's bite could have exerted around 1300 Newtons of force, comparable to the chomping power of modern humans and
several of our extinct cousins. But had it bitten down too vigorously on a
hard nut or a tough hunk of meat, the findings suggest Homo floresiensis
would have been at greater risk than our earlier human kin of straining
its facial bones, or dislocating the joint where the lower and upper
jaws meet.

"We don't really know what Homo floresiensis ate," said first author
Rebecca Cook, a doctoral student in evolutionary anthropology at
Duke. Patterns of wear on the teeth, combined with pygmy elephant bones
and other animal remains unearthed from the same cave where the Hobbit
was found suggest that it ate at least some meat.

But the results suggest that exceedingly hard or tough foods, which
would have been no problem for an australopith to gnaw on or crack open,
might have given the Hobbit a TMJ headache.

"Similar patterns are observed in modern humans," Cook said.

Millions of years of human evolution gave us smaller teeth and more
lightweight skulls, because cooking our food and slicing and pounding it
with stone tools, and probably also eating meat, made having overbuilt
skulls unnecessary.



==========================================================================
But years after the Hobbit's discovery its facial features remain a
puzzle. Its skull had a curious mix of traits, some of which -- like
its heavyset lower jaw -- are similar to our earlier and more ape-like ancestors, while others -- like its small delicate face -- resemble
humans today.

"This can make it confusing as to where this species falls on the family
tree of hominin evolutionary relationships," Cook said.

The new study suggests this shift to smaller faces, weaker bites and
achey jaws evolved early, before the common ancestors of Homo floresiensis
and modern humans went their separate ways.

Justin Ledogar, Duke researcher and senior author of the study, says the
next step is to do similar analyses on earlier members of the genus Homo, including Homo erectus. The first known hominin to use fire and cook food,
this species also had smaller teeth, jaws and faces than earlier hominins,
and is thought by some to be the ancestor of Homo floresiensis.

The researchers say the work could help answer lingering questions about
where Homo floresiensis came from, how it lived and how it fits into
the human evolutionary tree.

"This study is just one small piece of a much larger puzzle," Cook said.

This research was funded by the American Association of Physical
Anthropology and Duke University, and by grants from the European Union's Horizon 2020 Research and Innovation Programme (724046 SUCCESS) and the
U.S. National Science Foundation (NSF-BCS-0725126).

========================================================================== Story Source: Materials provided by Duke_University. Original written
by Ve'ronique Koch.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Rebecca W. Cook, Antonino Vazzana, Rita Sorrentino, Stefano Benazzi,
Amanda L. Smith, David S. Strait, Justin A. Ledogar. The cranial
biomechanics and feeding performance of Homo floresiensis. Interface
Focus, 2021; 11 (5): 20200083 DOI: 10.1098/rsfs.2020.0083 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210823110323.htm

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