I have to get all anthropological today because I was looking at something really cool in the lab. I'll put a bit of non-antho stuff at the bottom so if you are bored, just skip to the end.

I was measuring talus bones to see when the change over to bipedalism happened. It would have been even better if I had had some talus bones of fossil apes, but alas, not much survives when things are 4 million years old!

What I was looking at was the divergence of the big toe, the nature of the ankle joint and the orientation of the head and neck of the talus. I first measured a chimpanzee (Pan paniscus), which was to be a sort of model for fossil apes. This isn't too exact, because chimpanzees are just as modern as we are, and it's likely that there have been as many changes in their tarsals as in our tarsals. But for our purposes this is acceptable. The other talus I measured were from Australopithecus afarensis (Lucy) and Homo habilis, and a modern H. sapiens.

Here's a drawing showing the various measurements we took.

Alpha is a measure of the divergence of the big toe. Divergent big toes are found in chimpanzees and other Great Apes, it's for grasping tree branches etc. We (H. sapiens) have gotten rid of the divergence in favour of parallel toes. This gives us a much better platform for walking on, as all the force is directed straight ahead into the toes (there are other changes in the pelvic bones and the knees etc that I'm not going to mention because I was working on the talus bones). Gamma is the measurement of the rotation of the head of the tarsal joint. In chimpanzees and early hominids, the head is small and parallel to the bottom surface. This is because the joint is more mobile than ours, again for grasping...evidence of a more arboreal environment. In humans, the head is rotated up so it is almost perpendicular. It's also really large. This is to provide more contact surface, plus the bone itself is flatter and stouter. This leads to a less mobile joint (we can only flex and extend our ankles, can't really rotate very well) but to a stronger, more efficient forward-back movement...so we can walk easier, with the force again being directed in one direction. This allows us to walk faster and be more balanced. Look at a chimpanzee walking and you can see they have a much harder time of it than we do.

The Beta measurement is a measure of the flattening of the joint. In chimpanzees and hominids, the talus is very curved and elevated. It's also smaller. This leads again to a very mobile ankle joint, which is very advantageous to tree climbers. Since the talus is curved, this leads to a curved foot, which naturally grips branches better. In modern humans, the talus has gotten very stout and flat, because we don't generally use our feet for tree climbing...we use our feet as a platform to push off on.

The other measurements I took were the length of the head of the talus and the length of the whole talus. You can distinctly see that in the chimpanzee and the hominids, the neck of the talus is quite long and delicate. The overall length of the talus is quite long as well. This showes that they had longer, slenderer feet, again, advantageous in an arboreal environment. In H. sapiens, there is a massive reduction and broadening in the neck of the talus and the talus itself.

So I found that in general, there is a progression from A. afarensis to H. habilis to H. sapiens. You can see some traits appearing, such as the rotation of the head of the talus, the flattening of the talus and the length of the neck of the talus shortening. These traits all clearly show the shift towards bipedalism. Cool, eh?

Ok I'll talk about some more interesting things now. We had fencing tonight, the last practice before the Finals. I'm getting nervous. Chief had me work on some of the moves that I spontaneously started doing last tournament. I don't know where they came from, but they appeared, I can do them so I have a chance to kick butt now. I hope they stick around. I was exhausted fencing Chief though. We went back and forth, him attacking me and I had to parry-riposte him. Over the top, from the side, retreat while parrying and then counter time the attack. Fun stuff. I thought I was going to throw up, I was so overheated. I haven't felt like that since I used to run the 3,000m in track and field.