Sunday, 30 April 2017


Although I do try to bring you sciencey news in a timely fashion, I only have limited sources for primary information and limited time to scan them, so I missed this piece about the death of Lucy, AL288-1, the most complete representative of her species Australopithecus afarensis. She is not the type specimen; that honour goes to an adult mandible LH4 discovered in Laetoli, Tanzania described by Louis Leakey in 1976. Original article. AL129-1, aka Johansen's knee, shows the angle between femur and tibia that is typical of bipedal upright walkers. I met Johansen, Lucy's godfather,  when I was in graduate school. Lucy was an adult female but by no means a strapping wench, weighing in at about 50kg and 107 cm tall. She would have come up to my navel.
JBS Haldane [prev] had a brilliant essay On Being the Right Size which speculated about the effect of various animals falling down a mine shaft: A mouse walks away, a rat is killed, a man is broken, a horse splashes. They have now worked out in excruciating detail how Lucy died: falling from a great height probably out of a tree. Analysis of fossil pollen from the same geological strata as held Lucy for 3.5 million years shows that today's desert was then an open grassland with scattered trees. Australopithecus had clearly 'come down from the trees' because their knees and the angle between skull and neck vertebrae say that they spent most of the time walking upright  in the savanna. But it is suggested that, like chimpanzees and gorillas, they returned to trees to sleep, when threatened by predators and/or to forage for fruit and nuts. Some hold that upright posture is an adaptation to seeing over the tops of the grass. Our dentition and intestines have developed into something uniquely human because of cooking. It is unlikely that Lucy was high up in a tree so that she could munch through a load of leaves: fruit and nuts are more likely because they are quality food. The paper under discussion suggests that the anatomical changes involved in the switch to bipedal walking compromised our ability to scamper about in trees

ANNyway, the poor creature stepped on a rotten branch or missed her footing or got fatally distracted and fell to earth, possibly whacking off/through branches on the way down to an unforgivingly hard ground. The diagram [above L] shows how she may have broken her knee and ankle, then her pelvis, then her ribs and finally took a tonk to the head. That final blow is known as a guardsman fracture where the point of the lower jaw hits something hard and splits there are well as shearing off the condyles where the bone articulates with the skull: ouch!. That sort of bone damage is always accompanied by destructive internal injuries. At least it wasn't lingering.  Maybe it was slippy because she was caught in a tropical downpour, maybe that same deluge caused the distributary crevasse-splay channel which covered her broken body with preserving soil. My first proper scientific paper was an analysis of neogene tooth-metrics including Lucy's; I can't help but feel a sense of loss and a twinge of pain as I imagine her final 9.8 m/s2 gravity-accelerated plunge down to earth.

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