THE NEANDERTHALS were a type of primitive man who lived throughout much of Europe and western Asia for more than 200,000 years, but who disappeared less than 28,000 years ago. It is not known why they vanished and the latest thinking on this mystery is summarised by Kate Wong in Scientific American, August 2009. Climate change may have played a major part in the demise of the Neanderthals.
Two opposing hypotheses have vied to explain the relationship of Neanderthals to Homo sapiens. One proposed that Neanderthals were an archaic variety of our species that either evolved into or was assimilated by modern Homo sapiens. The other hypothesis proposed that Neanderthals were a separate species, Homo neanderthalensis, that were eliminated when modern humans entered their territory. Recent analysis of DNA recovered from Neanderthal remains shows little evidence of interbreeding with modern humans even though Neanderthals survived for 15,000 years after modern humans arrived in Europe a little over 40,000 years ago.
Neanderthals were more heavily muscled and larger boned than modern humans. The average Neanderthal man stood just over five feet tall. They were built to suit their lifestyle of ambush-hunting of large animals and gathering plant foods in a very cold climate. Neanderthals had longer heads (back to front) than we have, with low sloping foreheads. They had large faces and noses, and prominent brow ridges. On average, Neanderthals had slightly larger brains than we have. Their large heads and barrel- chested bodies were probably chosen by natural selection to conserve body heat in a cold climate.
Scholars now think that climate played a significant role in the demise of the Neanderthals. The Neanderthals were the only hominids (any primate of the Hominidae family including modern man and extinct precursors of man) in Europe between about 200,000 and 40,000 years ago. Climate scientists know that the climate in Europe was relatively moderate 65,000 years ago, but that ice sheets covered northern Europe 25,000 years ago. Neanderthals were the only hominids in Europe 65,000 years ago, but modern humans were the only hominids there by 25,000 years ago.
It is quite unlikely that a single swing from moderate to glacial conditions killed off the Neanderthals because they were well adapted to the cold and it is known that they survived glacial conditions before. However, it is now known that the period leading up to 25,000 years ago was climatically very unstable, swinging severely and suddenly from colder to warmer and back again. These oscillations were accompanied by ecological changes, eg forests giving way to treeless grasslands and reindeer replacing rhinoceroses. As Wong explains, within a person’s lifetime all the familiar animals and plants that he/she had grown accustomed to could be replaced by unfamiliar fauna and flora.
These sudden changes forced the hominid inhabitants of Europe to adopt new ways of life at short notice. Several successive climate changes over a relatively short period of time could also have reduced Neanderthal population numbers so severely that they simply died out.
So, how did modern humans survive these oscillating climate conditions if Neanderthals failed to beat this challenge? Wong describes research showing that early modern humans were much more flexible than the Neanderthals. Neanderthals seemed to have been fussy about what they ate. For example, some specialised in large mammals such as the relatively scarce woolly rhinoceros. When modern humans came into Neanderthal territory and began taking some of the rhinoceroses, the Neanderthals would have come under pressure. Modern humans on the other hand were not fussy and ate all sorts of plants and animals.
The Neanderthals were also probably at a disadvantage compared to early modern humans because of the way they gathered food. The Neanderthal concentration on large game probably meant that the entire community of men, women and children took part in the hunt with the women and children probably chasing the animals towards the men, who lay in wait to ambush them. On the other hand, the division of labour among early modern humans would have generated a more reliable food supply as well as providing a safer environment for rearing children. And finally, research has shown that Neanderthals required significantly more food energy to keep them going than did early modern humans, another factor that made them more fragile under pressure.
William Reville is associate professor of biochemistry and public awareness of science officer at University College Cork – http://understandingscience.ucc.ie
