Is Australopithecus afarensis Too Derived to be a Human Ancestor

My reaction on first hearing about this paper.
Having gotten that out of the way, I sat down and read the paper – which was published in PNAS. The paper was written by Yoel Rak, Avishag Ginzburg, and Eli Geffen. The short version is that Australopithecus afarensis displays mandibular traits that indicate it is too derived to be a human ancestor. The longer version is a little bit more interesting, although I am inclined to be somewhat skeptical.

Continue reading

Australopithecus afarensis and Apes: One from the Archives

I’m currently trying to get through a rather lengthy book – which I will be reviewing in a later post – so in the meantime here is one from the archives… I wrote it back in April of 2005 and think I would write it somewhat differently today. I’ve toyed with doing a similar post on the post-crania …
One of the most aggravating things one can hear, if one has any training in paleoanthropology, is that the australopithicines were nothing but glorified apes. So let’s study the issue (hey, I have to justify the name of this blog, okay! Which means more hominids.) The first set of pictures below is a frontal view of A. afarensis, a chimp, an orang and a gorilla.

Continue reading

The Juvenile Australopithecus afarensis

Back in August, 2005, I wrote a post on Dinosaur Embryos, Growth and Human Evolution. One section of the post discussed attempts to study the growth patterns of KNM-WT 1500, in particular, and Homo erectus in general. I followed the discussion with:

More intriguing is the possibility that this type of analysis could be extended to earlier fossils. Interesting fossils have been found in Drimolen, South Africa (about five years ago). The finds consisted of the bones of two infants. One was 2-3 years of age, the other 8-10 months. One is tentatively assigned to the genus Homo, the other to Australopithecus robustus (the interesting thing about the A. robustus infant was that a lot of the robustus traits were clearly visible on the fragments – indicating that even early in life their are species differences among the australopithecines). Although the finds were fragmentary and only few bits of the crania were found one wonders if in a few years the above type of analysis could be extended to these fossils as well.

Continue reading

Juvenile Australopithecus afarensis Found

Kambiz has the lowdown…I will have something to say as soon as I get the articles in question.

What Can You Learn From Bone Fragments?

Creationists frequently like to dismiss fossils by saying they are only fragments, with the implicit idea being that nothing can be learned from them. Yet, this is frequently not the case and the idea derives from a lack of knowledge of skeletal anatomy. So what can one learn from a fragment? Since the White et al paper published in Nature dealt with skeletal fragments let’s look at that and see what we can learn. In particular let’s look at the femur and the intermediate phalanx (which is complete, but interesting none the less).

Continue reading

Evolution of Human Limb Proportions: Part One

Humans have interesting limbs. Unlike in the apes, the humerus is shorter than the femur but longer than the radius. In chimps and gorillas the humerus is longer than the femur and radius. In orangutans and gibbons the humerus is longer than the femur but shorter than the radius. There are several measures anthropologists use to make these determinations. One, the humerofemoral index ([humerus x 100]/femur) measures the ratio of humerus to femur. In humans the mean of this index is (approximately) 71, in chimps 101, gorillas 116, orangutans 130 and in the gibbon 116. To compare the humerus and radius the brachial index ([radius x 100]/humerus) is used. Mean values are: humans 74, chimps 92, gorilla 80, orangutan 100 and gibbon 110. Since humans and chimps share a, relatively, recent common ancestor presumably some evolution has occured in limb proportions. We can look at the postcranial skeletons of a few hominids to determine a rough time line. Australopithecus afarensis, for example, has a humerofemoral index of about 84 (largely attributed to a smaller femur) and a brachial index of about 91 (larger radius relative to humerus). In Homo erectus, on the other hand the humerofemoral index is approximately 73 and the brachial index is 79 or roughly the same as in modern humans. So, during the course of human evolution there have been changes in forearm proportions and in femur length. For quite a while this was interpreted as an example of gradualism in hominin evolution. Then, the fly in the ointment was found.

Continue reading

Bipedal Locomotion in Australopithecus afarensis

Although I can walk bipedally, there has always been some debate about whether Lucy could. John Hawkes provides us with a link to an interesting paper on that issue. The full paper is available Journal of the Royal Society Interface. The authors of the paper applied concepts from evolutionary robotics to an analysis of bipedalism in humans, great apes and Lucy. There is also a quicktime movie – below is a picture from the movie.

Results indicate that A. afarensis was a “fully competent biped.” As Hawkes points out, there are several unknowns with the study that need to be addressed, but it was still interesting. Perhaps the most interesting aspect was the application of robotics and genetic algorithms (something I don’t know that much about)to the study of human evolution.

When I took Paleoanthropology, my term paper was on bipedality in A. afarensis – I took the position that they were fully competent bipeds – so I was really interested in this article.

On an unrelated note, while checking out the Royal Society website I came across this article on circadian clocks. I mention in case anyone out there, who knows a lot about such things, would be interested in explaining it to us.