Pinpointing the end of Neanderthals

What caused the demise of Neanderthals in Europe, some time around 28,000 years ago? Was it climate, or the arrival of modern humans? The conundrum exists partly because of problems establishing when events in the past actually happened. Polychronis Tzedakis and colleagues report, a way to relate Neanderthal remains to the palaeoclimate record.

All living things use carbon, mostly in the form of the isotope 12C, but a small proportion of carbon in the environment is the radioactive 14C. When an animal dies, the proportion of 14C is fixed and decays at a fixed rate. By measuring the amount of 14C in a fossil, and comparing it with the proportion thought to exist in the creature when it was alive, researchers can estimate the date the creature died.

The problem is that the proportion of 14C in the environment itself varies, which means that ‘radiocarbon’ years and actual calendar years don't always match. The discrepancy was especially marked at around the time the Neanderthals went extinct, making it hard to work out the chronology of their last days. Tzedakis and colleagues got round the problem by ignoring actual chronology completely. They relate radiocarbon years directly to palaeoclimate through a deep-sea core drilled in the Cariaco Basin, Venezuela, in which records of past climate can be related directly to radiocarbon date.

The team investigate three proposed dates for the end of the Neanderthals and find that the oldest two do not coincide with any extreme climate events. The youngest, and most controversial, occurs just before the final expansion of ice sheets, but this was a several 1000-year long gradual transition rather than an abrupt cold snap that would explain a sudden extinction.

CONTACTS

Polychronis Tzedakis (University of Leeds, UK)

Tel: +44 113 343 3300; E-mail: p.c.tzedakis@leeds.ac.uk

Please note the author is travelling but will be available on his mobile:

Tel: +30 697 221 9198