A new piece of research tries to help answer the question of how humans became bipedal. The researchers “tested” the hypothesis that carrying became easier with a bipedal gait by observing chimps in the field under conditions where resources were depleted, and found they adopted bipedalism in order to carry things better. QED.
On the BBC report this morning, an unusally savvy interviewer suggested that those pre-humans that walked on two legs would survive better than those that did not, and so here we are. A good Darwinian question, to which the lead researcher acquiesced.
But actually the paper doesn’t show that, does it? It show that chimps (and presumably, it is assumed, our common ancestor) already possess the ability to walk bipedally, which they usually don’t use much. We have no idea at all how they evolved that ability. All the chimps in the study walked thus, so it tells us nothing about variation and natural selection at all. One would have to hypothesise (as the paper seems to) that, with prolonged resource problems leading to long-term bipedalism and lots of carrying, some individuals showedanatomical variation that was adaptive. Eventually, the process was irreversible.
That’s very plausible, but is not shown by the ape study. In fact, the most obvious interpretation of the evidence is that chimps started walking bipedally because they needed to carry things, and that this acquired characteristic was inherited. Which is rather Lamarckian than Darwinian, don’t you think? In fact, it’s a kosher “Just So Story”, straight out of Kipling.
Now I have a theory about elephants, which have an ability to stretch their trunk if, for example, it is pulled by a crocodile. If there was once a prolonged period of high crocodile populations, one can envisage that some short-trunked elephants would show anatomical variations that enabled their trunk to stay stretched, leading to better survival. The crocodiles would thus constitute a selective pressure for longer trunks. What do you think? As the researcher said in the BBC interview, science progresses just one jigsaw piece at a time, but I reckon may be on to something.