Posted on 09/18/2007 8:47:54 AM PDT by SirLinksalot
Surprising research based on two African fossils suggests our family tree is more like a wayward bush with stubby branches, challenging what had been common thinking on how early humans evolved.
The discovery by Meave Leakey, a member of a famous family of paleontologists, shows that two species of early human ancestors lived at the same time in Kenya. That pokes holes in the chief theory of man's early evolution — that one of those species evolved from the other.
And it further discredits that iconic illustration of human evolution that begins with a knuckle-dragging ape and ends with a briefcase-carrying man.
The old theory is that the first and oldest species in our family tree, Homo habilis, evolved into Homo erectus, which then became human, Homo sapiens. But Leakey's find suggests those two earlier species lived side-by-side about 1.5 million years ago in parts of Kenya for at least half a million years. She and her research colleagues report the discovery in a paper published in Thursday's journal Nature.
The paper is based on fossilized bones found in 2000. The complete skull of Homo erectus was found within walking distance of an upper jaw of Homo habilis, and both dated from the same general time period. That makes it unlikely that Homo erectus evolved from Homo habilis, researchers said.
It is the equivalent of finding that your grandmother and great-grandmother were sisters rather than mother-daughter, said study co-author Fred Spoor, a professor of evolutionary anatomy at the University College in London.
The two species lived near each other, but probably did not interact, each having its own "ecological niche," Spoor said. Homo habilis was likely more vegetarian while Homo erectus ate some meat, he said. Like chimps and apes, "they'd just avoid each other, they don't feel comfortable in each other's company," he said.
There remains some still-undiscovered common ancestor that probably lived 2 million to 3 million years ago, a time that has not left much fossil record, Spoor said.
Overall what it paints for human evolution is a "chaotic kind of looking evolutionary tree rather than this heroic march that you see with the cartoons of an early ancestor evolving into some intermediate and eventually unto us," Spoor said in a phone interview from a field office of the Koobi Fora Research Project in northern Kenya.
That old evolutionary cartoon, while popular with the general public, is just too simple and keeps getting revised, said Bill Kimbel, who praised the latest findings. He is science director of the Institute of Human Origins at Arizona State University and was not part of the Leakey team.
"The more we know, the more complex the story gets," he said. Scientists used to think Homo sapiens evolved from Neanderthals, he said. But now we know that both species lived during the same time period and that we did not come from Neanderthals.
Now a similar discovery applies further back in time.
For the past few years there has been growing doubt and debate about whether Homo habilis evolved into Homo erectus. One of the major proponents of the more linear, or ladder-like evolution that this evidence weakens, called Leakey's findings important, but he wasn't ready to concede defeat.
Dr. Bernard Wood, a surgeon-turned-professor of human origins at George Washington University, said in an e-mail Wednesday that "this is only a skirmish in the protracted 'war' between the people who like a bushy interpretation and those who like a more ladder-like interpretation of early human evolution."
Leakey's team spent seven years analyzing the fossils before announcing it was time to redraw the family tree — and rethink other ideas about human evolutionary history. That's especially true of most immediate ancestor, Homo erectus.
Because the Homo erectus skull Leakey recovered was much smaller than others, scientists had to first prove that it was erectus and not another species nor a genetic freak. The jaw, probably from an 18- or 19-year-old female, was adult and showed no signs of malformation or genetic mutations, Spoor said. The scientists also know it is not Homo habilis from several distinct features on the jaw.
That caused researchers to re-examine the 30 other erectus skulls they have and the dozens of partial fossils. They realized that the females of that species are much smaller than the males — something different from modern man, but similar to other animals, said study co-author Susan Anton, a New York University anthropologist. Scientists hadn't looked carefully enough before to see that there was a distinct difference in males and females.
Difference in size between males and females seem to be related to monogamy, the researchers said. Primates that have same-sized males and females, such as gibbons, tend to be more monogamous. Species that are not monogamous, such as gorillas and baboons, have much bigger males.
This suggests that our ancestor Homo erectus reproduced with multiple partners.
The Homo habilis jaw was dated at 1.44 million years ago. That is the youngest ever found from a species that scientists originally figured died off somewhere between 1.7 and 2 million years ago, Spoor said. It enabled scientists to say that Homo erectus and Homo habilis lived at the same time.
All the changes to human evolutionary thought should not be considered a weakness in the theory of evolution, Kimbel said. Rather, those are the predictable results of getting more evidence, asking smarter questions and forming better theories, he said.
I see nothing in this article, nor in such as Caesar’s posts, which has anything to do with refuting evolution generally. Thus, accusing them of “defending” is totally moot because that’s not at all what they’re doing. They’re talking about details within the ET.
The last thing I read about “Luci” was that she was an Orangutan and that her broken jaw was put together wrong to make it look like a prehuman.
I’m a conservative “scientific” God&Jesus-believer.
I don’t know if Genesis is literally true, or analogically true (searching for correct term there), or if “evolution” as postulated now is true.
I don’t think 1 necessarily precludes the other at all.
I think it’s all very interesting, but I’m not any kind of biological researcher. Neither am I a great Bible scholar, though I have read the American version completely through (the Gospels many times).
You read incorrect information.
Try scientific sites rather than creationist sites and you'll get more accurate information.
Wish I could watch YouTube here.
“Scientists usually seem to be on the side of athiests. Being a “thinker” doesn’t mean you’re thinking the right things.”
To be a “Conservative” means you have to be religious? I don’t agree!
No, he was a product of German philosophy. Darwin, like most Brits his age, was strongly influenced by German idealism , also, and Darwinism as an intellectual movement, as opposed to the theory, was also. Darwin himself was amazed by the boldness of his German supporters.
Of course they lived side by side until one competed the other out of the niche. How is this new information?
This is true of most supposed human fossils. Either these different supposed human species existed contemporaneously (judging by the dating given by paleoanthropologists themselves), the difference in skull/body shape falls within the range of contemporary human morphology, or these fossils simply represent extinct ape species.
The fossil evidence for human evolution is shockingly flimsy. I'm in the middle of reading Bones of Contention. I highly recommend it.
If you accept the underlying premise that Homo habilis and Homo erectus lived at the same time then that is a clear indication that there were multiple, distict, ape-like animals on Earth at the same time. How do you reconcile that with either Intelligent Design or Creationism?
So what does this fossil record do to Intelligent Design or Biblical creationism? How would either explain that?
Do you think a theory was proven wrong and not replaced with a better one?
By 'interact' I don't think that they mean that Homo habilis ate Homo erectus. I think they're talking about procreating.
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