Biological anthropologists question claims for human ancestry

February 16, 2011, New York University

"Too simple" and "not so fast" suggest biological anthropologists from the George Washington University and New York University about the origins of human ancestry. In the upcoming issue of the journal Nature, the anthropologists question the claims that several prominent fossil discoveries made in the last decade are our human ancestors. Instead, the authors offer a more nuanced explanation of the fossils' place in the Tree of Life. They conclude that instead of being our ancestors the fossils more likely belong to extinct distant cousins.

"Don't get me wrong, these are all important finds," said co-author Bernard Wood, University Professor of Human Origins and professor of Anatomy at GW and director of its Center for the Advanced Study of Hominid . "But to simply assume that anything found in that time range has to be a human ancestor is naïve."

The paper, "The evolutionary context of the first hominins," reconsiders the evolutionary relationships of fossils named Orrorin, Sahelanthropus and Ardipithecus, dating from four to seven million years ago, which have been claimed to be the earliest human ancestors. Ardipithecus, commonly known as "Ardi," was discovered in Ethiopia and was found to be radically different from what many researchers had expected for an early human ancestor. Nonetheless, the scientists who made the discovery were adamant it is a human ancestor.

"We are not saying that these fossils are definitively not early human ancestors," said co-author Terry Harrison, a professor in NYU's Department of Anthropology and director of its Center for the Study of . "But their status has been presumed rather than adequately demonstrated, and there are a number of alternative interpretations that are possible. We believe that it is just as likely or more likely that they are fossil apes situated close to the ancestry of the living great ape and humans."

The authors are skeptical about the interpretation of the discoveries and advocate a more nuanced approach to classifying the fossils. Wood and Harrison argue that it is naïve to assume that all fossils are the ancestors of creatures alive today and also note that shared morphology or homoplasy – the same characteristics seen in species of different ancestry – was not taken into account by the scientists who found and described the fossils. For example, the authors claim that for Ardipithecus to be a human ancestor, one must assume that homoplasy does not exist in our lineage, but is common in the lineages closest to ours. The authors suggest there are a number of potential interpretations of these fossils and that being a human ancestor is by no means the simplest, or most parsimonious explanation.

The scientific community has long concluded that the human lineage diverged from that of the chimpanzee six to eight million years ago. It is easy to differentiate between the fossils of a modern-day chimpanzee and a modern human. However, it is more difficult to differentiate between the two species when examining fossils that are closer to their common ancestor, as is the case with Orrorin, Sahelanthropus, and Ardipithecus.

In their paper, Wood and Harrison caution that history has shown how uncritical reliance on a few similarities between fossil apes and humans can lead to incorrect assumptions about evolutionary relationships. They point to the case of Ramapithecus, a species of fossil ape from south Asia, which was mistakenly assumed to be an early human ancestor in the 1960s and 1970s, but later found to be a close relative of the orangutan.

Similarly, Oreopithecus bambolii, a fossil ape from Italy shares many similarities with early human ancestors, including features of the skeleton that suggest that it may have been well adapted for walking on two legs. However, the authors observe, enough is known of its anatomy to show that it is a fossil ape that is only distantly related to humans, and that it acquired many "human-like" features in parallel.

Wood and Harrison point to the small canines in Ardipithecus and Sahelanthropus as possibly the most convincing evidence to support their status as early . However, canine reduction was not unique to the human lineage for it occurred independently in several lineages of apes (e.g., Oreopithecus, Ouranopithecus and Gigantopithecus) presumably as a result of similar shifts in dietary behavior.

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12 comments

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Sean_W
3.4 / 5 (11) Feb 16, 2011
I agree that some may be a bit too fast to call a fossil a *direct* ancestor. But "cousin" species can be useful in knowing about our lineage since they were living at the same time/climate and were probably not that far removed from our line. Anyway, I will now get out of the way so that the creationists can try to somehow spin this into a defeat for evolutionary theory.
DontBeBlind
1 / 5 (10) Feb 16, 2011
qvqoebel your comment is just a sad attempted to keep creobots from shinning a little light in your dark narrow mind.
This topic always gives me a good laugh. These educated people really think we evolved from apes. Well apes is only one of the steps in their stupid theory. But it gives the best laugh value.
arofibook
3.7 / 5 (3) Feb 16, 2011
The crappy thing is that the creationists will cherry pick some of the info from this article.
Terrible_Bohr
3.5 / 5 (6) Feb 16, 2011
This topic always gives me a good laugh. These educated people really think we evolved from apes. Well apes is only one of the steps in their stupid theory. But it gives the best laugh value.

We didn't evolve from apes; we share a common ancestor with them. If you don't even understand the _very_ basics of human evolution, it really undermines your credibility when criticizing it.

But hey: at least you're not a hypocrite when you mock people with an education!
Quantum_Conundrum
1 / 5 (8) Feb 16, 2011
Terrible Bohr:

You may share a common ancestor with them, but "we" do not.

Quit hijacking real science and biology with your crackpot psuedoscience.
LivaN
5 / 5 (1) Feb 17, 2011
Quantum_Conundrum:
Terrible Bohr:

You may share a common ancestor with them, but "we" do not.

Not all of us are lucky enough to be made of sand and dirt.
Yellowdart
1 / 5 (4) Feb 17, 2011
We didn't evolve from apes; we share a common ancestor with them.


Who's name is?

Perhaps all the "creobots" are confused when you never name what that ancestor is...

Honestly, all this article shows is the constant lack of clarity amongst anthropologists.
Terrible_Bohr
5 / 5 (1) Feb 17, 2011
You heard it here folks: Quantum Conundrum will now redefine science for us all! I hope he takes away the math component, because that shit is hard!

@ Yellowdart: Wait for it. Scientists aren't just making answers up on demand. Is it not enough to now for now that we have human ancestors in the ground AND proof of human and ape genetic similarity?

Let's get Johannes and all the others in here, too: It's easy to reach a consensus when no one's actually doing any interpertation of data, but rather are being spoon-fed the answers. You can sit there in a position of comfort with a complete and unfalsifiable creation myth, or you can accept the tangible evidence around you for evolution. You can choose to reject the idea that life evolves, but please be so kind as to offer some sort of alternative theory based on observations rather than faith.
Blue_Hat
5 / 5 (1) Feb 18, 2011
Terrible_Bohr - we not only share a common ancestor with apes and evolved from apes, humans are apes. We just happen to be the upright walking and talking ones.

As for the article - not much to argue. Until we get a more complete fossil record for the Pan/Hominin split, it's impossible to say which fossil apes are in our phylogenetic lineage.
Michael_David
not rated yet Feb 23, 2011
One thing that bugs me, is you criticize Darwin your assumed to be a creationist. I am a strong believer in evolution. I just think that evolution according to Darwin is limited. And that there needs to be many revisions.

I just think Darwin is becoming more and more outdated. And that within evolution on a galactic scale with millions of planets just in our galaxy likely capable of developing life that evolution is not exclusively local. In other words, I think evolution is scaled up to even potentially differing verities and cross pollinations in different regions of the galaxy. But that is too far ahead of potential data right now.
Ethelred
not rated yet Feb 24, 2011
One thing that bugs me, is you criticize Darwin your assumed to be a creationist.
Because it is almost always the case. Even in many of the cases where the poster refuses to admit to being a creationist such as Dogbert.
I am a strong believer in evolution. I just think that evolution according to Darwin is limited.
Have you read it? What do you think the limit is? What are your problems with it?
And that there needs to be many revisions.
He has a been dead for rather a long time so I don't think Charlie is going to revise it. Again. He wrote six editions. HOWEVER when people speak of Darwin they usually really mean moder evolutionary theory which include genetics and LOTS of revisions so I would have to say that you haven't a clue as to what you are talking about.
I just think Darwin is becoming more and more outdated.
I think you have learned anything about modern evolutionary theory that you didn't get from a Creationist.

More
Ethelred
not rated yet Feb 24, 2011
within evolution on a galactic scale with millions of planets just in our galaxy likely capable of developing life that evolution is not exclusively local.
What does that have to do with evolution on Earth and the processes that have been going on here? Nothing.
In other words, I think evolution is scaled up to even potentially differing verities and cross pollinations in different regions of the galaxy.
Have you smoking strange stuff? Reading the Book of Urantia? Do you know that we have no evidence of life on other planets yet? While it is likely there is extraterrestrial life it is unlikely to be able to interbreed with life on Earth.
But that is too far ahead of potential data right now.
Also irrelevant to the evolution of life on Earth.

So would you care to share with us some specifics on your reservations about the evolution of life on Earth and the process of natural selection? Please stick with the Earth as anything else is rampant speculation.

Ethelred

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