Monday, 24 November 2014

3,200.040 years BC

Forty years ago this morning 24 Nov 1974, Don Johanson wrote in his diary that he was "feeling really lucky".  A few hours later, he found a few fragments of the fossil hominid that he was looking for. He was on an expedition with two French anthropologists, Maurice Taieb and Yves Coppens, looking for 'the missing link' - fossil evidence of transitional forms between modern humans and the great apes our nearest living relatives.  At the end of the day, sitting round the camp-fire with the Beatles "Lucy in the Sky with Diamonds" playing again (there was a limited repertoire available in the middle of an Ethiopian desert), someone suggested that the fossils fragments should be named Lucy - and by breakfast the next morning it was so.  Some people claim that, as Lennon was cranked up on LSD when he wrote the song, so drugs had been taken the night our renote ancestor was discovered.  Even after weeks of intensive work in widening circles round the original find, only 40% of the skeleton was recovered and only a couple of fragments of skull.  The picture L from Patrick Clarkin, shows what we know in pink with the rest 'reconstructed' and filled in. The first bits Johansen found were crucially bits of the knee, which showed that his fossil was knock-kneed rather than bow-legged like apes, which can and do walk upright but it's a hirple for them but normal for us and for Lucy.  The other piece of crucial information was the date, which we now agree to be about 3.2 million years ago.  That came from the analysis of the relative amounts of potassium and argon (it's the radio-active decay, stupid) in nearby volcanic rocks.  There is a key leap of faith required because volcanic rocks don't have fossils, and sedimentary rocks don't have the K/Ar clock. A bit of stitch and match is required.

Lucy (AL-288-1 officially) was only 110cm tall but probably a female (the pelvis has a couple of different possible re-constructions) and definitely an adult from the complete ossification of the epiphyses of the bones and the eruption of, and wear to, the third molars aka wisdom teeth.  The skull fragments show that she was small brained like other apes and the knees show that she walked upright, so it settled a debate about brain early or bipedal early. I like this very much because I buy into the idea that the hand drove the brain.  Freeing the hand from any constraint for locomotion means that it can start sewing, flint-knapping, spear-crafting and designing fish-hooks; not to mention make jewellery and other fripperies to impress the opposite sex. It needs an ever bigger brain to cope with these ever multiplying artifacts (bangles to Saturn V rocket, say): we are Homo faber, in the coinage of Hannah Arendt, of banality of evil fame.

As it happens, I met Johanson, about ten years after Lucy changed his life entirely, when he was the guest of my friend-and-mentor Lynn Margulis at BU when I was still in graduate school.  I had just completed a catalogue of hominid teeth, including Lucy's, with another of my friend-and-mentors called Ben Blumenberg.  On the back of cranking some hundreds of tooth metrics through a mainframe computer to generate comparative statistics we said something profound about the human condition - I can't remember what it was though.  Johanson was charming and I didn't bore him too much before fading into the background and leaving him to talk to a real evolutionist like Margulis.  I haven't been there, but I've talked to the T-shirt.

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