The primitive technologies that our early ancestors left behind gradually evolve, and comparing finds dated to different times can advance understanding of our own evolutionary trajectory. ‘We think the evolution to modern humans is associated with changes in behaviour and in technology, for example in their tool use. We’ve already found evidence that they started using animal bones to make tools, which was rare in earlier populations,’ says Mirazón Lahr. ‘The people who lived around here 10,000 years ago used microliths – a form of miniaturised stone tool technology,’ adds her colleague Foley. ‘Instead of producing one or two big flakes like the earliest modern humans, they produced lots of very small flakes to make composite tools. We’ve also found a beach in the Turkana Basin from about 200,000 years ago and that has its own very different fossilised fauna, and very different stone tools. The technology and the people changed a lot during the past 200,000 years.’
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Mirazón Lahr emphasises that geography and climate played a critical role in the origins and diversification of modern humans. ‘The times when the lakes were high were periods of plenty in East Africa,’ she says. ‘When it was very wet there were lots of animals to hunt, the vegetation could grow, and you can imagine that the people would have thrived.’ East Africa had a unique mosaic environment with lake basins, highlands and plains that provided alternative niches for foraging populations over this period. ‘We think that early modern humans could live in the region throughout these long periods, even if they had to move between basins.’ With a network of habitable zones, human populations survived by expanding, contracting and shifting ranges according to the state of the environment at any given time.
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By comparing the fossil records from different basins over time, Mirazón Lahr is trying to establish a spatial and temporal image of human occupation over the past 200,000 years. She believes that the way to find novel insights is to consider each problem from various angles. Drawing on her wide-ranging interests from molecular genetics to prehistory, and combining genetic, fossil, archaeological and palaeoclimatic information, she hopes to form an accurate and complete picture of our early ancestors’ lives and the external forces that shaped their evolution, both biological and behavioural.
