Early human ancestor didn't have the jaws of a nutcracker, study finds

February 8, 2016
The fossilized skull of Australopithecus sediba specimen MH1 and a finite element model of its cranium depicting strains experienced during a simulated bite on its premolars. "Warm" colors indicate regions of high strain, "cool" colors indicate regions of low strain. Credit: Image of MH1 by Brett Eloff provided courtesy of Lee Berger and the University of the Witwatersrand.

Research published in 2012 garnered international attention by suggesting that a possible early human ancestor had lived on a diverse woodland diet including hard foods mixed in with tree bark, fruit, leaves and other plant products.

But new research by an international team of researchers now shows that Australopithecus sediba didn't have the jaw and necessary to exist on a steady diet of hard foods.

"Most australopiths had amazing adaptations in their , teeth and faces that allowed them to process foods that were difficult to chew or crack open. Among other things, they were able to efficiently bite down on foods with very high forces," said team leader David Strait, PhD, professor of anthropology in Arts & Sciences at Washington University in St. Louis.

"Australopithecus sediba is thought by some researchers to lie near the ancestry of Homo, the group to which our species belongs," said Justin Ledogar, PhD, Strait's former graduate student and now a researcher at the University of New England in Australia. "Tet we find that A. sediba had an important limitation on its ability to bite powerfully; if it had bitten as hard as possible on its molar teeth using the full force of its chewing muscles, it would have dislocated its jaw."

The study, published Feb. 8 in the journal Nature Communications, describes biomechanical testing of a computer-based model of an Australopithecus sediba skull. The model is based on a fossil skull recovered in 2008 from Malapa, a cave near Johannesburg, South Africa. The biomechanical methods used in the study are similar to those used by engineers to test whether or not planes, cars, machine parts or other mechanical devices are strong enough to avoid breaking during use.

Australopithecus sediba, a diminutive pre-human species that lived about two million years ago in southern Africa, has been heralded as a possible ancestor or close relative of Homo. Australopiths appear in the fossil record about four million years ago, and although they have some human traits like the ability to walk upright on two legs, most of them lack other characteristically human features like a large brain, flat faces with small jaws and teeth, and advanced tool-use.

Humans in the genus Homo are almost certainly descended from an australopith ancestor, and A. sediba is a candidate to be either that ancestor or something similar to it.

Some of the researchers who described A. sediba are also authors on the biomechanical study, including Lee Berger, PhD, and Kristian Carlson, PhD, of the University of the Witwatersrand, and Darryl de Ruiter, PhD, of Texas A&M University. Amanda Smith, PhD, a postdoctoral fellow in physical anthropology at Washington University, also participated in the research.

The new study does not directly address whether Australopithecus sediba is indeed a close evolutionary relative of early Homo, but it does provide further evidence that dietary changes were shaping the evolutionary paths of early humans.

"Humans also have this limitation on biting forcefully and we suspect that early Homo had it as well, yet the other australopiths that we have examined are not nearly as limited in this regard," Ledogar said. "This means that whereas some australopith populations were evolving adaptations to maximize their ability to bite powerfully, others (including A. sediba) were evolving in the opposite direction."

"Some of these ultimately gave rise to Homo," Strait said. "Thus, a key to understanding the origin of our genus is to realize that ecological factors must have disrupted the feeding behaviors and diets of australopiths. Diet is likely to have played a key role in the origin of Homo."

Strait, a paleoanthropologist who has written about the ecological adaptations and evolutionary relationships of early humans, as well as the origin and evolution of bipedalism, said this study offers a good example of how the tools of engineering can be used to answer evolutionary questions. In this case, they help us to better understand what the facial skeleton can tell us about the diet and lifestyles of humans and other primates.

"Our study provides a really nice demonstration of the difference between reconstructing the behaviors of extinct animals and understanding their adaptations." Strait said. "Examination of the microscopic damage on the surfaces of the teeth of A. sediba has led to the conclusion that the two individuals known from this species must have eaten hard foods shortly before they died. This gives us information about their feeding behavior. Yet, an ability to bite powerfully is needed in order to eat hard foods like nuts or seeds. This tells us that even though A. sediba may have been able to eat some hard foods, it is very unlikely to have been adapted to eat hard foods."

The bottom line, Strait said, is that the consumption of hard foods is very unlikely to have led natural selection to favor the evolution of a feeding system that was limited in its ability to bite powerfully. This means that the foods that were important to the survival of A. sediba probably could have been eaten relatively easily without high forces.

Explore further: Fossilized teeth provide new insight into human ancestor

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BartV
1.4 / 5 (9) Feb 08, 2016
"Humans in the genus Homo are almost certainly descended from an australopith ancestor...."


Total junk science based on an unproven guess. There is no science in these kind of statements. Best to leave them out.

viko_mx
1 / 5 (7) Feb 08, 2016
How many components are needed to be built the simplest living cell that has the basic features in the living organisms: Permanent internal conditions - stasis that ensure stable metabolism needed for its energetic needs, cell membrane with conditional permeability inward and outward, carrier of genetic information - DNA , and mechanisms for the reading of this information, transcription and subsequent synthesis of needed for the cell proteins in the right moment and their consequent spatial folding in the final 3d shape, system for the restoration of the structure of DNA and the original genetic information recorded in it, the complex system for the reproduction without that the existence of a cell is severely limited in time.
How this necessary cell structures can be synthesize and survive in the external environment if are not protected by its membrane. What is the point of their existence when they are outside the cell, from the viewpoint of non-coincidence randomness?
antialias_physorg
5 / 5 (6) Feb 08, 2016
"Humans in the genus Homo are almost certainly descended from an australopith ancestor...."

Total junk science based on an unproven guess. There is no science in these kind of statements. Best to leave them out.

Funnily enough, if you had checked the link at the bottom of the article it could have saved you your (false) assertion.
viko_mx
1 / 5 (6) Feb 08, 2016
... and of course accessible food at one cell membrane distance, which usually is product of living organisms, because this simplest cell have self driving functionality.
viko_mx
1 / 5 (6) Feb 08, 2016
...have no self driving functionality.
relmasian
5 / 5 (4) Feb 08, 2016
Amazing that pseudo-science, Darwin fearing trolls seem to frequently post at phys.org. I suppose trying to divert others keeps their own brains busy, maybe even happy.
viko_mx
1 / 5 (5) Feb 08, 2016
The evolution theory mumbo jumbo have not scientific explanations. You also have no scientific arguments. Оnly emotional protest against truth.The main purpose the eugenics anti scientific ideology of evolution is defense of sin. In practice this ideology was born much before Darwin to became its official spokesman. The main serious problem of it is that can not rely on scientific facts. And this did not go unnoticed by observant people.
Torbjorn_Larsson_OM
5 / 5 (4) Feb 08, 2016
"Amazing that pseudo-science, Darwin fearing trolls seem to frequently post at phys.org."

They have nothing better to do while their mothers aren't looking down the cellar since they don't know they biological function of their junk or anything else as their comments attest to. But it isn't as if their stupid claims would pass a 5 year old with web access:

"Evolution is a cornerstone of modern science, accepted as one of the most reliably established of all facts and theories of science, based on evidence not just from the biological sciences but also from anthropology, psychology, astrophysics, chemistry, geology, physics, mathematics, and other scientific disciplines, as well as behavioral and social sciences."

[ https://en.wikipe...volution ]

They think their magic superstition beats rubbing two neurons together or help against natural processes like brain death taking their persons. The joke is on them.
24volts
not rated yet Feb 08, 2016
"Tet we find that A. sediba had an important limitation on its ability to bite powerfully; if it had bitten as hard as possible on its molar teeth using the full force of its chewing muscles, it would have dislocated its jaw."

That has got to be one of the stupidest statements I've ever read. What animal dislocates it's jaw just because it bites down on something as hard as it can?
yep
5 / 5 (2) Feb 08, 2016
BartV and Viko apparently you are not aware scientists have suppressed gene expression in chickens and grew embryos with dinosaur snouts!
This ability kind of confirms that whole evolution thing....
FESTtheory
1 / 5 (1) Feb 10, 2016
FINALLY SOLVED : The human evolution must consider the evolution of IQ, but I have found only "the evolution of emotions". These three processes intersect at one point - baby .That is not an evolutionary mistake, on the contrary, that is the key element. By observing his mother's behavior, a process called MSP/multi self-projection passively occurs in baby's brain when child perceives guardians body as his own. That way infant's CNS immediately learns the shortest way to get something done which enables the creation of many more similar thinking processes till the moment when a minimal number of thinking processes (Adam's number) are required in order to effect of self-consciousness arise. https://evolutionofhumanintelligence.wordpress.com/

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