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Is This Your Long-Lost Ancestor?

The views expressed are those of the author and are not necessarily those of Scientific American.

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Australopithecus sediba skull

Skull of juvenile male Australopithecus sediba. Image: Kate Wong

In the spring of 2010, the world met Australopithecus sediba, a nearly two-million-year-old human relative whose remains were found at a site just a short drive from Johannesburg, South Africa. By all accounts, it was an extraordinary discovery: two beautifully preserved partial skeletons–a juvenile male and an adult female–with the promise of more individuals to come. The fossils exhibit a striking mix of traits combining features of the primitive australopithecines (Lucy’s ilk), such as a small brain, with features associated with our own genus, Homo—small teeth, for instance. The anatomical mash-up led the discovery team to place them in a new species and to propose that it could be the ancestor of Homo. Spirited debate ensued.

Fast forward to this past September, when the team published a second round of papers on the fossils, this time delving deeper into details of A. sediba’s anatomy. The mosaic theme continued. In that tiny brain, for example, the researchers spotted signs of a more Homo-like reorganization of gray matter; in its hand they observed gracile digits (an australopithecine-like trait) paired with a long thumb that would have enabled a humanlike precision grip; in its foot they found an apelike heel bone accompanying a humanlike ankle bone.  The list goes on and on.

The A. sediba fossils cut to the very heart of a burning question about human evolution: namely, where did Homo come from? Paleoanthropologists have lots of australopithecine fossils, and a wealth of later Homo fossils. But they have precious few clues about the origin of our genus. Could A. sediba be our long-lost ancestor? If discoverer Lee Berger of the University of the Witwatersrand and his team are right, their fossils could topple some cherished ideas about how we became human.

I’ve come to Johannesburg to get a better handle on this incredibly exciting and complex story. I’ve been visiting with Berger and his colleagues at the University of the Witwatersrand to learn about the A. sediba fossils and how the team is teasing information out of them. I’ll be hanging out with the researchers all week, checking out the fossils, interviewing team members, and visiting the discovery site (where more fossils are waiting to be unearthed). And I’ll be posting updates here in the Scientific American Observations blog. So please follow along and ask any questions in the comments section below. I’ll do my best to get you answers—and your feedback will help me write a feature article on this game-changing discovery.





Kate Wong About the Author: Kate Wong is an editor and writer at Scientific American covering paleontology, archaeology and life sciences. Follow on Twitter @katewong.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. fyngyrz 1:18 pm 11/29/2011

    My long-lost ancestor? No. But it kind of looks like my memory of my ex-wife.

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  2. 2. JohnOstrowick 1:50 pm 11/29/2011

    If you’re in Joburg (any other people on this site…) – go to the origins museum – – they’re pretty helpful and that’s where Sediba was originally displayed after her/their discovery.

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  3. 3. JacobSilver 8:53 pm 11/29/2011

    Brain size is not as important as organization. Also, if he first human had the genetic abnormality to cause neoteny, that alone would cause an increase in brain size. But, of course, the problem is not the first human, though it may have looked just like us. But with whom did he or she mate. Then the off springs would have only had recessive human traits. So, it would have taken four or six generations before we got a set of male and female humans.

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  4. 4. hemo_jr 9:43 pm 11/29/2011

    Provided that there were some way to determine if the FOX2P gene in A.sediba was the same as in modern humans, that could be the deciding point in determining whether they should be renamed H.sediba.

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  5. 5. apriljohn 10:57 pm 11/29/2011

    In discovering this our long lost ancestor which is the sediba that has stated in this article, it will help us increase our scientific knowledge and views. But for me this could not convinced me that this sediba is my long lost ancestor.

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  6. 6. Sauce23 7:07 am 11/30/2011

    Lee Berger has quite vaguely hinted about soft tissue and tools. Is there a chance that you can try to tease out something more concrete about these topics during your visit?

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  7. 7. JamesDavis 9:02 am 11/30/2011

    There is no way that can be a modern human’s ancestor, unless it is already human! And if it is human, where did it come from and how? To the knowledge on this planet, there is no animal that can metamorphose itself into another animal without something manipulating its DNA. And since you do not believe in intelligent alien life forms visiting this planet millions of years ago, that leaves a virus or bacteria that can manipulate DNA. If that is the case then, “NASA, we have a problem!”

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  8. 8. Dredd 9:00 am 12/1/2011

    Are there any inquiries yet, or even any techniques or methods, as to whether or not microbes had yet become symbiont to that species as they are to Homo today?

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  9. 9. Wayne Williamson 1:26 pm 12/3/2011

    James, I can’t tell if your post is tongue in cheek or if your anti evolutionary….I believe what they are saying is this is some where between a “lucy” and another one of our ancestors like homo erectus…

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