Anthropologist finds explanation for hominin brain evolution in famous fossil

May 07, 2012
The soft spot and metopic suture are visible on the skull of the young human (right) and absent in the young chimpanzee (left). Those features are present, although harder to see, in the fossil of a young Australopithecus africanus (center). Image: Marcia Ponce de León and Christoph Zollikofer/University of Zürich

(Phys.org) -- One of the world’s most important fossils has a story to tell about the brain evolution of modern humans and their ancestors, according to Florida State University evolutionary anthropologist Dean Falk.

The Taung fossil — the first australopithecine ever discovered — has two significant features that were analyzed by Falk and a group of anthropological researchers. Their findings, which suggest was a result of a complex set of interrelated dynamics in childbirth among new bipeds, were published May 7 in the Proceedings of the National Academy of Sciences.

“These findings are significant because they provide a highly plausible explanation as to why the hominin brain might grow larger and more complex,” Falk said.

The first feature is a “persistent metopic suture,” or unfused seam, in the frontal bone, which allows a baby’s skull to be pliable during childbirth as it squeezes through the birth canal. In great apes — gorillas, orangutans and chimpanzees — the metopic suture closes shortly after birth. In humans, it does not fuse until around 2 years of age to accommodate rapid brain growth.

The second feature is the fossil’s endocast, or imprint of the outside surface of the brain transferred to the inside of the skull. The endocast allows researchers to examine the brain’s form and structure.

After examining the Taung fossil, as well as huge numbers of skulls belonging to apes and humans, as well as corresponding 3-D CT (three-dimensional computed tomographic) scans, and taking into account the fossil record for the past 3 million years, Falk and her colleagues noted three important findings: The persistent metopic suture is an adaptation for giving birth to babies with larger brains; is related to the shift to a rapidly growing brain after birth; and may be related to expansion in the frontal lobes.

“The persistent metopic suture, an advanced trait, probably occurred in conjunction with refining the ability to walk on two legs,” Falk said. “The ability to walk upright caused an obstretric dilemma. Childbirth became more difficult because the shape of the birth canal became constricted while the size of the brainincreased. The persistent metopic suture contributes to an evolutionary solution to this dilemma.”

The later fusion of the metopic suture is most likely an adaptation of hominins who walked upright to be able to more easily give birth to babies with relatively large brains. The unfused seam is also related to the shift to rapidly growing brains after birth, an advanced human-like feature as compared to apes.

“The later fusion was also associated with evolutionary expansion of the frontallobes, which is evident from the endocasts of australopithecines such as Taung,” Falk said.

The Taung , which is estimated to be around 21Ž2 million years old, was discovered in 1924 in Taung, South Africa. It became the “type specimen,” or main model, of the genus Australopithecus africanus when it was announced in 1925.

An australopithecine is any species of the extinct genera Australopithecus or Paranthropus that lived in Africa, walked on two legs and had relatively small brains.

Falk conducted the research with Marcia S. Ponce de Leon, Christoph P.E. Zollikofer and Naoki Morimoto of the Anthropological Institute and Museum at the University of Zurich in Switzerland.

Explore further: Divers sure of new finds from 'ancient computer' shipwreck

More information: “The metopic suture of Taung (Australopithecus africanus) and its implications for hominin brain evolution,” by Dean Falk et al. PNAS (2012)

Related Stories

'You will give birth in pain': Neanderthals too

Apr 21, 2009

(PhysOrg.com) -- Researchers from the University of California at Davis (USA) and the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) present a virtual reconstruction of a female Neanderthal ...

Peking man differing from modern humans in brain asymmetry

Jun 28, 2011

Paleoanthropologists studying the fossil endocasts of Australopithecus, Homo habilis, Homo erectus, Neanderthals, and Homo sapiens have reported that almost all brain endocasts display distinct cerebral asymmetry. ...

A fetus can sense mom’s psychological state

Nov 10, 2011

(Medical Xpress) -- As a fetus grows, it’s constantly getting messages from its mother. It’s not just hearing her heartbeat and whatever music she might play to her belly; it also gets chemical signals through the ...

Recommended for you

'Jaws' lived in Doncaster according to fossil record

Sep 15, 2014

(Phys.org) —Sharks, swamps and a tropical rainforest teeming with life – it's not what comes to mind when you think of Yorkshire. But for the first time evidence of Doncaster's 310-million-year-old past, ...

Ancient Greek tomb dig finds marble statues

Sep 11, 2014

Archaeologists slowly digging through a huge 2,300-year-old tomb in northern Greece have uncovered two life-sized marble female statues flanking the entrance to one of three underground chambers.

User comments : 12

Adjust slider to filter visible comments by rank

Display comments: newest first

verkle
1.2 / 5 (26) May 07, 2012
Explanation for evolution? Little basis for it. The article is comparing apples and oranges. No need to try to link us to chimpanzees. Let's study brains, but don't waste time trying to tag it to an unproven theory. Humans are made wonderfully different.

Turritopsis
1 / 5 (16) May 07, 2012
Brain development can be linked to external influence of many sorts. Environmental changes influence epigenetic evolvement throughout an organisms lifetime, these accumulated changes are inherited by the descendants of the lifeform. These are 2 separate drivers which merge in evolution. Inherited genes and developing alterations of genes.

Should outside forces be involved, genetic evolution could be accredited to higher dimensional lifeforms molding and reshaping organisms, a sort of genetic reprogramming if you will, Earth and the lifeforms residing on it and in it could be a running simulation driven and controlled by extradimensional beings. They may have even gifted us with self evolving abilities, like an advanced mandlebrot equation with changing fractal properties. Reality could be a self evolving simulation stemming from a singular equation.
Turritopsis
1 / 5 (6) May 07, 2012
And obviously mutations coupled with natural selection. Also, interspecies copulation can result in new genetic lineage, like species 0, the origin.
simplicio
4.9 / 5 (15) May 07, 2012
genetic evolution could be accredited to higher dimensional lifeforms molding and reshaping organisms, a sort of genetic reprogramming if you will, Earth and the lifeforms residing on it and in it could be a running simulation driven and controlled by extradimensional beings. They may have even gifted us with self evolving abilities, like an advanced mandlebrot equation with changing fractal properties. Reality could be a self evolving simulation stemming from a singular equation.

I can think much more fantastical 'maybes', but so what? Things like that is unscientific by not being testable. Do you have a test for it?
simplicio
4.8 / 5 (18) May 07, 2012
Explanation for evolution? Little basis for it. The article is comparing apples and oranges. No need to try to link us to chimpanzees. Let's study brains, but don't waste time trying to tag it to an unproven theory. Humans are made wonderfully different.

I think you are not very educated.
chardo137
3.3 / 5 (10) May 07, 2012
I am guessing that verkle has two strikes: 1. Uneducated 2. Republican. I realize that these two things are synonyms, I just thought that it needed to be said.
Turritopsis
1.7 / 5 (6) May 07, 2012
The suture may remain unfused until the 2nd year as a result of an expanding brain, and not as stated:
In humans, it does not fuse until around 2 years of age to accommodate rapid brain growth.


The theory states the cause for brain growth and expansion is the unfused metopic suture (that the brain grows into the accommodating skull), while the retardation of the fusion may be caused by the pressure of the expanding and growing brain on the skull.

The latter is much more plausible of the 2 IMO. It is because of the brains rapid expansion that the metopic suture doesn't fuse, and not, that the persistent metopic suture causes expansion of the brain.

IOW, if brain expansion persisted in other great apes as it does in humans their metopic suture would remain unfused for a longer period just as it does in humans.
Telekinetic
5 / 5 (6) May 08, 2012
verkle:
Your disassociation from chimpanzees would make you less than human:
"The (Borna) virus now turns out to have an intimate bond with every person on Earth. In the latest issue of Nature, a team of Japanese and American scientists report that the human genome contains borna virus genes. The virus infected our monkey-like ancestors 40 million years ago, and its genes have been passed down ever since."- Carl Zimmer, N.Y. Times
CHollman82
5 / 5 (8) May 08, 2012
Explanation for evolution? Little basis for it. The article is comparing apples and oranges. No need to try to link us to chimpanzees. Let's study brains, but don't waste time trying to tag it to an unproven theory. Humans are made wonderfully different.



Hi, did u go 2 colage? Wat is ur degre in? U must be smrt to say evoluton no hapen, how u know?
LordKinyambiss
5 / 5 (9) May 08, 2012
Evolution denial is very revealing of human nature. How can the majority of people in the world (6.5) Billion choose to ignore the reality regarding our origins and by implication our destiny. One of the results of 'a larger brain' is the ability to think up fantastical lands in the clouds full of all the things that evolution has created such as fruits, birds, people with wings..lol Its a side effect of a larger brain since the majority of us are unable to reconcile scientific fact with our reality choosing instead, the world of fairies.
KatLom
not rated yet May 08, 2012
I find it odd that this article makes no mention of Raymond Dart, the anthropologist who first examined this skull after its discovery, and proposed that it represented a new species of Australopithecus. However, because Dart was not part of the scientific establishment, and because he found the fossil in Africa, and not Europe or Asia, where the establishment supposed man's origins, his findings were dismissed.
IronhorseA
5 / 5 (1) May 08, 2012
Evolution denial is very revealing of human nature. How can the majority of people in the world (6.5) Billion choose to ignore the reality regarding our origins and by implication our destiny. One of the results of 'a larger brain' is the ability to think up fantastical lands in the clouds ...


Obviously a touch of madness is a side effect of a larger brain. ;P