"Lucy" not direct ancestor of humans?

[TithonusSyndrome]

Tel Aviv researchers make a bold claim

Tel Aviv University anthropologists say they have disproven the theory that "Lucy" - the world-famous 3.2-million-year-old Australopithecus afarensis skeleton found in Ethiopia 33 years ago - is the last ancestor common to humans and another branch of the great apes family known as the "Robust hominids."

The specific structure found in Lucy also appears in a species called Australopithecus robustus. Prof. Yoel Rak and colleagues at the Sackler School of Medicine's department of anatomy and anthropology wrote, "The presence of the morphology in both the latter and Australopithecus afarensis and its absence in modern humans cast doubt on the role of [Lucy] as a common ancestor."

The robust hominids were discovered in southern Africa 69 years ago and are believed to have lived between 2 million and 1.2 million years ago. Their jaws and jaw muscles were adapted to the dry environment in which they lived.

Rak and colleagues studied 146 mature primate bone specimens, including those from modern humans, gorillas, chimpanzees and orangutans and found that the "ramus element" of the mandible connecting the lower jaw to the skull is like that of the robust forms, therefore eliminating the possibility that Lucy and her kind are Man's direct ancestors. They should therefore, the Israeli researchers said, "be placed as the beginning of the branch that evolved in parallel to ours."

Their research has just been published in the on-line edition of PNAS, the Proceedings of the [US] National Academy of Sciences.

Lucy, which means "you are wonderful" in Amharic, was discovered (40 percent of its skeleton) by the International Afar Research Expedition in Ethiopia's Awash Valley. Fitting the bones together, they said it was an upright walking hominid (Homo sapiens, which comprises modern Man and extinct manlike species). They later found its jaws and additional bones.

Further analysis led the Afar researchers to believe it was of a female, and the skeleton listed as AL 288-1 was nicknamed Lucy because the Beatles' song "Lucy in the Sky With Diamonds" was often played at the camp.

The specimen was only 1.1 meters tall, estimated to weigh 29 kilograms and look somewhat like a common chimpanzee. Although it had a small brain, the pelvis and leg bones were almost identical in function with those of modern humans, proving that these hominids had walked erect.

Although fossils closer to chimpanzees have been found since then, Lucy - which is housed in the national museum in Addis Ababa - is prized by anthropologists who study Man's origin.

Rak and his colleagues also wrote that the structure of Lucy's mandibular ramus closely matches that of gorillas, which was "unexpected" because chimpanzees are the closest living relatives of humans, and not gorillas.

Well, that kinda sucks. How many specimens like Lucy remain in favor of evolution?

[Surlethe]

What do you mean, "in favor of evolution"? If anything, this new development is simply more confirmation of evolution: it fits beautifully with the prediction that life should not be linear, but should branch like a tree.

[TithonusSyndrome]

What do you mean, "in favor of evolution"? If anything, this new development is simply more confirmation of evolution: it fits beautifully with the prediction that life should not be linear, but should branch like a tree.

That makes a lot more sense than the anti-evolution screed this article was presented to me under.

[Rye]

Yeah, it's entirely possible Lucy was just a different type of bipedal ape, rather than a member of a specific ancestral species that humans directly descended from. Could just as easily be a cousin species to our ancestor species of the time she inhabited.

[Surlethe]

What do you mean, "in favor of evolution"? If anything, this new development is simply more confirmation of evolution: it fits beautifully with the prediction that life should not be linear, but should branch like a tree.

That makes a lot more sense than the anti-evolution screed this article was presented to me under.

When you're looking at anti-evolution propaganda, you have to be sure to keep in mind what the theory of evolution really is: its central postulates and predictions. Creationists almost have no choice but to strawman evolution because they have no idea what it is; they don't understand it, and all too often don't take the time to learn about it anyway. As unfair as it is, when you're in a debate with a creationist, you have to shoulder the burden of going over everything presented and making sure that it's not a strawman of evolution, because once you accept a creationist's strawman of evolution, he's already two-fifths of the way to convincing you.

[wolveraptor]

It's extremely unlikely that we'll ever find the exact species that marks the split between the branches of hominids and the other apes. However, the numerousness of ape-like ancestors who are likely members of sister lineages to our own effectively guarantee that at some point, humans were related to apes. Besides, this discovery doesn't change anything about later Australopithecine species. It may, however, cause Lucy to be reclassified.

[Akhlut]

Interesting read, but I'm a bit skeptical that the ramus alone is 'disqualifying' Australopithecines as ancestors of modern hominids that aren't of the robust type. While I freely admit that I'm not a primate specialist, I'd think that modifications to jaw structure over a million year period would be very feasible and that the branch between robust hominids and other hominids could have come at a point later than Lucy (unless genetic studies say otherwise, of course).

On the other hand, anatomical differences between great apes are generally not that great, especially with the advent of bipedalism. Aside from the skull, I suppose there's not that much of a difference between most hominids and that the ramus would be a fairly important area of differentiation between different branches of hominids.

But I'm still skeptical that this alone would indicate that Australopithecines aren't ancestors of modern humans.