Lucy's Cousin

Nature news reports the finding of a new australopithecine in Ethiopia only 35km from the site where Lucy, Australopithecus afarensis, was discovered in 1974. Lucy marked one of the oldest examples of early hominins at that time, living as she did approximately 3.2 million years ago. She has a relatively small cranium, which means a small brain, but was clearly bipedal; thereby resolving the chicken and egg question in relation to large brain capacity and bipedalism. Her skeleton is 40% complete, which is remarkably intact for a specimen that old, and we have learnt an awful lot from her.

This new specimen is contemporaneous with A. afarensis, being 3.3-3.5 million years old, which throws up the scenario that there were possibly several early hominins all wondering around east Africa at the same period. But this shouldn't come as a surprise, it is only in very recent history that we became the only biped on the block when we finished off the last of the neanderthals; before then there had been as many as half a dozen species cohabiting in Africa and through into Asia. Part of the reason that this could happen is demonstrated in the new skeleton. It has a much sturdier and stronger jaw than Lucy does, this would imply that they had a different diet and therefore weren't competing for the same resources.

This new species has been dubbed Australopithecus deyiremeda which roughly translates as 'close relative' in the local Afar language. We shouldn't assume that she (I'm calling her a she) is our ancestor, however, many early hominins died out and weren't a part of the lineage that went on to become the Homo genus. That said, she does make for a wonderful transition fossil, which turns out to have been something of a theme on the blog this week. I shall try to transition into a new area next week.

Model of what Lucy, and possibly A. deyiremeda, may have looked like

I Love Transition Fossils

One of the many stupid arguments put forward by people trying to dispute the theory of evolution by natural selection is: if evolution is true then there should be fossils of missing links, if birds evolved from dinosaurs then show me a fossil that is half bird and half dinosaur. Now, asides from the fact that this shows a gross misunderstanding of the theory there are actually a great deal of 'missing links' out there; they're called transition fossils and there is now a quite beautiful catalogue of them. We have transition fossils for pretty much every major order of animals out there, the only exception I can think of is bats, we don't yet have a decent fossil record of their evolution - it's only a matter of time, though.

We have ambulocetus, a wonderful cetacean (whale and dolphin) precursor that could swim well and walk around on land too; we have tiktaalik, a transition fossil of a fish that had 4 primitive legs and was well on its way to being an amphibian; and we have the legendary archaeopteryx, which is quite literally half bird half dinosaur. The fossil record, by its very nature, will never be 100% complete, but it is now well stocked with a plethora of transition fossils all of which add support to the now invincible edifice that is evolution by natural selection, and, I'm pleased to say we can now welcome another strut to the structure.

Image used with permission

An article in Nature has given details of an awesome new transition fossil; it is quite clearly a snake but equally clearly it has four little legs. The legs would not have allowed it to walk, they're too small and it's body is too long, but they may have allowed it to grab prey a little easier or get a better grip when mating hence its name: Tetrapodophis amplectus which translates as four-legged hugging snake.

For a long time it was uncertain if snakes had evolved from land animals or aquatic animals. If the latter then we would expect to see a transition fossil with a tail adapted for swimming and vestigial fins; if the former then we would expect, well, we would expect exactly what this fossil shows. Another little gap in our knowledge has been filled in, leaving one less place for evolution deniers to hide.