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Department of Palaeontology, The Natural History Museum, London SW7 5BD, UK
One of the most serious past difficulties facing realistic tests of evolutionary models for modern human origins was the lack of widely applicable dating procedures that could reach beyond the practical limits of radiocarbon dating. Moreover, the amount of fossil material that had to be sacrificed to obtain a conventional radiocarbon date meant that human fossils could generally only be dated indirectly through supposedly associated materials. Because of these limitations, the transition from Neanderthals to modern humans in Europe was believed to have occurred about 35 000 radiocarbon years ago, but detailed reconstruction of the processes involved (for example, evolution or population replacement) was not practicable. In the Levant, the transition period from Neanderthals to modern humans was believed to lie only slightly beyond this 35 000-year watershed. Elsewhere, in Africa, east Asia and Australasia, the chronology for modern human origins was even more difficult to establish. However, over the last fifteen years, radiocarbon and non-radiocarbon physical dating techniques such as luminescence and electron spin resonance have been increasingly refined, leading to a revolution in our understanding of the timescale for human evolution, particularly for the last 200 000 years. Although each dating method has its own strengths and weaknesses, the picture that now emerges is one of a gradual evolution of Neanderthal morphology in Europe, in parallel with a similar evolution of modern humans in Africa. Modern humans also appear surprisingly early in the Levant (c. 100 ka ago) and Australia (c. 60 ka ago). However, many uncertainties still surround the process of establishment of our species globally.
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