Just over two decades ago, as the new millennium began, it seemed that tracks left by our ancient human ancestors dating back more than about 50,000 years were excessively rare.
Homo heidelbergensis. For the most part, the surfaces on which the East African tracks occur have had to be laboriously and meticulously excavated and exposed.Homo sapiens
Excavation is therefore not usually considered – and because of the sites' exposure to the elements and the relatively coarse nature of dune sand, they aren't usually as well preserved as the East African sites. While this limits the potential for detailed interpretation, we can have the deposits dated. That's where optically stimulated luminescence comes in.A key challenge when studying the palaeo-record – trackways, fossils, or any other kind of ancient sediment – is determining how old the materials are.
Given how the tracks in this study were formed – impressions made on wet sand, followed by burial with new blowing sand – it is a good method as we can be reasonably confident that the dating"clock" started at about the same time the trackway was created.Firstly, the sediments are rich in quartz grains, which produce lots of luminescence.
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