The puzzle is one of the greatest surrounding our species. On a planet that bristled with different types of human being, including Neanderthals and the Hobbit folk of Flores, only one is left today: Homo sapiens.
Our current solo status on Earth is therefore an evolutionary oddity — though it is not clear when our species became Earth’s only masters, nor is it clear why we survived when all other versions of humanity died out. Did we kill off our competitors, or were the others just poorly adapted and unable to react to the extreme climatic fluctuations that then beset the planet?
These key issues are to be tackled this week at a major conference at the British Museum in London, “When Europe was covered by ice and ash,” when scientists will reveal results from a five-year research program using modern dating techniques to answer these puzzles.
In particular, researchers have focused on the Neanderthals, a species very close in physique and brain size to modern humans. They once dominated Europe, but disappeared after modern humans arrived after emerging from our African homeland about 70,000 years ago. The question is: why?
“A major problem in understanding what happened when modern humans appeared in Europe has concerned the dates for our arrival,” Chris Stringer of the Natural History Museum in London said. “It was once thought we appeared in Europe about 40,000 years ago and that we coexisted with Neanderthals for thousands of years after that. They may have hung on in pockets — including caves in Gibraltar — until 28,000 years ago, it was believed.”
In other words, there was a long, gradual takeover by modern humans — an idea that is likely to be demolished at this week’s conference, Stringer added.
Results from the five-year research program, RESET (Response of humans to abrupt environmental transitions), will show that humans arrived much earlier than previously estimated and that Neanderthals expired even more quickly. Careful dating of finds at sites across Europe suggests that Homo sapiens reached Europe 45,000 years ago. Five thousand years later, Neanderthals had disappeared. This latter finding is particularly striking.
“All previous research on Neanderthal sites, which have suggested that they were more recent than 40,000 years old — and there have been a lot of them — appear to be wrong,” Stringer added. “That is a key finding that will be discussed at the conference.”
Using radiocarbon technology to date remains that are 40,000 years old has always been tricky. Radioactive carbon decays relatively quickly and after 40,000 years there will only be a tiny amount left in a sample to measure. The tiniest piece of contaminant can then ruin dating efforts.
However, scientists working for the RESET program have set out to get round these problems. At Oxford University, scientists led by Tom Higham have developed new purification methods to prevent contamination and have been able to make much more precise radiocarbon dating for this period.
In addition, scientists have discovered that there was a devastating eruption of the Campi Flegrei volcano west of Naples 39,000 years ago. Recent studies have shown this eruption was much more destructive than previously recognized.
More than 250km3 of ash were blasted into the atmosphere and covered a vast area of eastern Europe and western Asia. This layer gives scientists a precise means of dating for this period and, combined with the new radiocarbon dating, shows there are no Neanderthal sites anywhere in Europe that are less than 39,000 years ago, a date 10,000 years older than previous estimates. It is a significant shift in our thinking about our nearest evolutionary cousins.