Native people in Australia have been spoiled for choice of materials from which to make superb stone tools, all kinds of silica rock being available in the bedrock and the widespread tropical soils, including multicoloured chalcedony and even opal. Their master craftsmen developed a form of heat treatment that subtly modifies silica’s internal structure so that gentle application of pressure to the edges of lumps removes small flakes to give intricate sharp edges, including barbs for fishing spears. This pyrotechnology leaves easily recognised signs in stone tools: colour changes and a pearly lustre.

A large team of archaeologists and geoscientists from South Africa, Australia, the UK and France have sifted through tools collected from the 35 to 280 ka African Middle Stone Age (defined differently from the European Mesolithic) in search of evidence for fire treatment (Brown, K.S. and 8 others 2009. Fire as an engineering tool of early modern humans. Science, v. 325, p. 859-862). Like signs of symbolic behaviour (see Technology, culture and migration in the Middle Palaeolithic of southern Africa and Deeper roots of culture in January and March 2009 issues of EPN) fire-worked silica tools appear as early as 164 ka ago. However, this is the first paper that reports a search for such technology, and since fire was definitely used by even earlier humans, such as Homo antecessor around 790 ka (see Early, microscopic evidence for human control of fire in November 2008 issue of EPN) expect earlier finds to be announced.

See also: Webb, J. and Domansski, M. 2009. Fire and stone. Science, v. 325, p. 820-821

Neanderthals few on the ground

Analysis of DNA from Neanderthal bones is gathering pace as cheaper and more reliable methods for sequencing emerge. The latest breakthrough is by a team working in Svante Pääbo’s lab at the Max-Planck Instuitute for Evolutionary Anthropology in Leipzig, Germany, which has defined full mitochondrial DNA sequences for five individuals (Briggs, A.W. and 17 others 2009. Targeted retrieval and analysis of five Neandertal mtDN genomes. Science, v. 325, p. 318-321). The samples are from almost the full geographic range known for Neanderthals, from Spain in the west to the eastern shore of the Black Sea in Russia, and are from 38 to 70 ka old; i.e. probably pre-dating the main influx of fully modern humans into Europe. The results show that the range of genetic diversity in the female line was only one third that found in humans today. That suggests that, compared with the modern human diaspora from Africa, total numbers of Neanderthals was low over the period analysed, and perhaps since their first colonisation of Europe and the Eurasian steppes around 400 ka.

See also: Wong, K. 2009. Twilight of the Neandertals. Scientific American, v. 301 (August 2009), p34-39.

Klondike gold rush pays dividends for Pleistocene

The 1896 discovery of gold in the Yukon Territory, Canada triggered the Klondike gold rush, which led to environmental wreckage that continues to this day. The placer deposits are in permanently frozen, but fragile alluvial sediments dating back as far as 700 ka. But as well as gold washed in by the Yukon’s rivers, the permafrost contains exceptionally well preserved records of the area’s late Pleistocene flora and fauna. The reason why that was possible at such high latitude (65ºN) through 6 or 7 glacial interglacial cycles is that it remained free of ice sheets for most of the Pleistocene. Fossils finds in the placer deposits therefore document the conditions on the western edge of the Bering Straits land bridge, or Beringia, which emerged each time that sea level fell during glacial maxima (Froese, D.G. et al. 2009. The Klondike goldfields and Pleistocene environments of Beringia. GSA Today, v. 19 (August 2009), p. 4-10). Beringia was the route presented to the earliest Asian human migrants into the Americas, possibly even before the Last Glacial Maximum 22 ka ago. Much of the evidence comes from wind-blown loess deposits that are prone to permafrost development. Also, being close to a number of active volcanoes the area was sporadically blanketed by ash deposits that are dateable by radiometric means, so a stratigraphy is possible even in the irregular and ice-disturbed sediments. During glacial episodes the area was steppe dominated by herds of bison, mammoths and horses; clearly a hunters paradise, despite the harsh conditions.