Tuesday, October 03, 2006

Lucy's Ancestor

There's nothing worse than having a skeleton and you don't know what it is. ~ Tim White

In 1974, Donald Johansen and his team found the bones of a hominid that they named Lucy. This turned out to be a bit informal, so they later dubbed it Australopithecus afarensis. The completeness of Lucy's skeleton enabled scientists to learn about about her. Most importantly, they learned that she was bipedal, which was a revelation. Lucy was apparently our earliest ancestor found to that time.

Hominid bones are extremely rare. Probably this is because, first, there weren't many of them relative to other species. Second, it appears that they tasted good to the various predators, so hominid bones got crunched and munched and scattered about. What bones are found are often a bit here and a bit here. A significantly complete skeleton is a find to get scientific blood coursing.

But, anthropologists are often cautious about making rash judgments. Partly, I think it's the ghost of Piltdown Man haunting them. In addition, there is the danger of making a preliminary finding that's overturned when others have a chance to review the evidence. At best, this leads to embarrassment, while at worst it can lead to divisions within the field. In a field as speculative as the study of early Man, divisions have been common enough.

So, it's not surprising that we are just now hearing about a group of bones that were initially discovered in 2000. The bones are still encased partially in a block of sandstone, but, after five years of hard work, a team led by Zeresenay Alemseged from the Max Planck Institute For Evolutionary Anthropology, has begun to free the bones. And they have revealed Lucy's little sister.

Well, not exactly. Actually, the Dikika girl (named for the area where she was found) is considerably older than Lucy, running about 3.3 millions of age. Articles are also calling the child Lucy's baby, all of which is catchy as all get out. What's important is that these are the bones of a child of about 3 years old. A. afarensis finds are extremely rare to begin with; juveniles are almost unheard of.

So why is it so important that we find young hominids? Well, it's just like finding juvenile dinosaurs; scientists can learn a great deal from juveniles by their developmental stages.

The completeness of this skeleton has already produced some interesting findings. The bones include the torso, parts of the arms and legs, and, most importantly, the skull and brain case. That last has revealed that the child's brain was smaller than that of a chimp of similar age. Why does this matter? Chimp brains grow to their maximum size more quickly than human brains (we're slow developers; what can I say?). For Lucy's baby to have a brain at a similar level of development to modern humans indicates that A. afarensis had already diverged significantly from the line that leads to modern chimps.

The find is so well preserved that the team also found a hyoid bone. This is a delicate bone found in the tongue which is necessary for speech, which is not to say that Australopithecenes were chatting among themselves about what wine to have with scavenged kill. In fact, the hyoid is similar to the one found in apes rather than the one in modern humans. What makes it important is that it's the first found in any hominid species other than a single Neanderthal hyoid.

It's becoming clear that A. afarensis was a great climber as well as an upright walker. No doubt, they felt as comfortable in the trees as they did on the ground, perhaps more so. Lucy and her kin, therefore, are not to be considered to be fully human by any stretch, but they were “stepping” in the right direction.

There's still a huge amount of work to be done on the skeleton, and it's probable that even more findings will be made as the bones are freed from their sandstone encasement.

But you can bet there's a bunch of happy anthropologists doing it.

Resources used in this article:

The amazing fossil of 'Lucy's little sister

'Lucy's baby' found in Ethiopia

Earliest Baby Girl Ever Discovered: Australopithecus Afarensis Child Sheds Light On Human Evolution

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