Monday, 20 August 2012

Watch the birdy!

Charles Darwin wasn't an expert on birds, and we can forgive him that. He collected a huge pile of birds on the Galapagos, but didn't pay them much attention at the time. On his return home, they were passed to an ornithologist friend for identification. The ones that have passed into the scientific history books - later known as Darwin's Finches - aren't actually proper finches, but a group of twelve or more species of fairly dull-looking birds that turned out to be very important in demonstrating some of Darwin's ideas.

What he noticed about these finches is that while at first glance they were fairly similar, their beaks were adapted to suit their individual lifestyles and diets - adaptive radiation - and the species varied from island to island. Darwin noted "one might really fancy that one species had been taken and modified for different ends." This idea was expanded on in 'Origin'.

 A few years ago, a study of one of the group - the excitingly named medium ground finch - showed their beaks had changed noticeably over two decades, as individuals with shorter beaks were better able to cope with competition with the recently arrived large ground finch. Shortbeaks fed better and bred more successfully, meaning... well, you get the idea. Recently, the genome of of Medium (for short) has been determined, and and further adaptation will be carefully tracked at genetic level.

Thursday, 9 August 2012

A man in time

Homo rudolfensis had been known from solitary skull found by Lake Turkana in Kenya in 1972, and has seen a couple of name changes since. On discovery, it was thought the skull belonged to Homo habilis and was maybe 3 million years old, but the differences were significant enough to merit a new name, Pithecanthropus rudolfensis, in 1978. A change of heart shortly after led to its 'promotion' back to the human genus and it became Homo again, while further date testing gave an age of 1.9 million years old.

Part of the assignation problem was that the skull had to be reconstructed from lots of little bone fragments. A 3d jigsaw without all of the pieces and with the picture on the lid long since lost. The first assembly give Rudolf a flat face and a relatively large brain capacity. A computer make-over carried out in 2007 threw in some observations on mammalian facial features that had been made since the initial work and the result was quite a different face. The jaw was now far more pronounced, and the team rather cruelly shrank the brain in accordance with the slope of the jaw. This proved a controversial decision, with a few skullologists ( I made that word up. There might be such a thing as a craniologist, though. Look it up.) rushing to the defence of Rudolf. So, the 2007 lobotomy might not stand.

Recently, more H. rudolfensis material has been found, from three individuals, again in Kenya. These finds support the decision to give it a separate species name, with dental details differing from other species. They date between 1.95 and 1.78 million years old, which makes rudolfensis contemporary with not only Homo habilis, but also H. ergaster and H. erectus. It's been a while since we threw out the old idea of a single lineage of human ancestry leading back to some crouching, grunting apeman, but our understanding of the story is filling out all the time. It's nice to think our ancestors had a few related species kicking around as they considered a long walk North, and I'm sure there are still more finds to be made.