Origin of Man: Recent Studies Challenge The Accepted Evolutionary Tree For Humans
By on September 9th, 2011

The Human Evolutionary Tree might need revision. Recent studies and analysis of the fossil of a skull discovered in South Africa in 2008 suggest that a new species, Australopithecus sediba, might have been the earliest human ancestor. The skull of the creature shows both human and ape-like characteristics. Homo habilis, the accepted earliest human ancestor, might have to be relegated to the status of a failed species.

The new species on the block

A. sediba dates back to a period two million years ago. This means that it predates Homo habilis by 77,000 years! The skeletons of A.sediba discovered are thought to belong to a female of about 30 years of age and that of a teenage male. They died together, possibly hours apart. The skeleton still shows bits of skin attached to it!

The Skull of Australopithecus sediba

Making Tools and Using them too

What makes A.sediba an exciting prospect is the fact that the species could make and use tools, a fact we can infer from the brain size and the shape of the fingers. X-ray scans of the skull of the young male fossil showed the braincast of the creature. Once the skull cast is known, scientists can work backwards, tracing the marks in the skull and location of the various artery marks to determine the shape and size of the brain. It turns out that the brain was a quarter of the size of the modern human brain, but still bigger than a chimpanzee’s or even Homo habilis‘s. What is more thrilling is the shape of the hands.

The hands of A.sediba had long thumbs, meaning they could do precision work with tools, much like us. This suggests that they could probably make tools and use them! In fact, the grip of A.sediba might have been better than our own, given the fact that the thumb was longer than ours.

The bigger brained and better tool-making A.sediba might really have been our ancestor, rather than Homo habilis. So what of Homo habilis?

What happens to our Evolutionary Tree?

Then

In the accepted view of the evolution of the human species, Homo habilis represents the first creature in the Homo lineage that leads directly to us, Homo sapiens. Homo habilis gave way to Homo erectus, which then split into Homo sapiens and Homo neanderthalensis (Neanderthals). The H.neanderthalensis species went extinct and H.sapiens came to dominate as the only species in the Homo genus. (Look at the graphic below)

The human timeline (Courtesy: National Geographic)

Now

Now, A.sediba challenges that. It aims to replace H.habilis as the first creature that bore human characteristics, rather than ape-like ones. This means that H.habilis is relegated to being a mere species which went extinct, rather being a transitional form for modern humans. It was, by all means, a failed species that just couldn’t survive the evolutionary competition. However, more research and debate needs to be done to establish this hypothesis.The final word has not been said!

One thing is for sure : We are just Children of Africa searching for our own origins, our place in the cosmos and where we came from.

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Author: Debjyoti Bardhan Google Profile for Debjyoti Bardhan
Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.

Debjyoti Bardhan has written and can be contacted at debjyoti@techie-buzz.com.
 
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