Modern humans may well have evolved from hardy Neanderthals who suffered through a dramatic cold spell that descended on Europe about 40,000 years ago, according to a new study that throws another coal into the already heated scientific debate about our origins.
The report, published this week in the journal Proceedings of the National Academy of Sciences, disagrees with the widely held belief that humans' early ancestors came in waves out of Africa to overwhelm the separate and distinct Neanderthal populations of Europe.
Rather, the study suggests, scientists should revert to an earlier notion that Homo sapiens emerged from Neanderthals ( Homo neanderthalensis), who, for still unknown reasons, eventually died out.
"It seems that the Neanderthals were not completely erased," argued study author Eugène Morin, an anthropology professor at Trent University in Peterborough, Ont.
To make his eyebrow-raising conclusions, Prof. Morin examined bone beds in western France dating from 40,000 years ago to 35,000 years - considered the major transition period in the biological and cultural development of modern humans.
It was during that period when new tools began being used, artistic tendencies such as cave drawing emerged, and more modern-day anatomical features came about - things not immediately associated with primitive Neanderthals.
"These changes," Prof. Morin explained, "have nothing to do with population replacement, but rather with a population decline and an adaptation to a harsher climate."
Prof. Morin examined animal bones recovered from an area of limestone cliffs in Saint-Césaire from that transition period. It was in that region, in 1979, that a Neanderthal skeleton was recovered, and where later, a complete stratigraphy of the time period was created and eventually where thousands of artifacts and animal remains were unearthed.
Excavations uncovered everything from bison to wooly rhinos to cave lions and wolves. But what Prof. Morin discovered as he moved forward in time was a dramatic increase in the number of reindeer and narrow-skulled voles - both animals are well-adapted to cold climates - while the myriad other animals went into a sharp decline.
"During this 5,000-year time period, the landscape changed from a northern temperate climate to a sub-arctic climate," Prof. Morin said.
It would have been a tough, inhospitable existence for new arrivals, and the land would not have been able to support as many people, he surmised. When the diversity of animals decreased, leaving largely reindeer herds, the numbers of the humans who depended on them would have shrunk through a series of "population bottlenecks," he argued.
At the same time, a genetic drift, the spreading of a genetic aberration in a previously isolated group of people, would have taken place, he said. That is the process whereby certain genetic traits vanish or are passed on. During this cold snap, Neanderthals might have roamed more widely in search of food and connected neighbouring human populations, a process that would have also injected more modern traits into the Neanderthal gene pool.
Prof. Morin concluded that some groups of Neanderthals began evolving into modern humans while other groups did not, and died out.
Prof. Morin presented his findings last year to a conference, and they raised a lot of questions among his peers.
After all, in 2004, another group of scientists reported the "most concrete evidence to date" that Neanderthals were not contemporary humans' ancestors through an analysis of skulls belonging to humans, Neanderthals and non-human primates.
Two years later, a study of the Neanderthal genome concluded that while humans and Neanderthals had a common ancestry - in fact, they share a genome that is 99.5 per cent identical - the two split at one point and evolved quite separately.
Scientists widely believe that both Neanderthals and early Homo sapiens lines existed at the same time, may have done very little inbreeding, and that between 32,000 and 24,000 years ago, Neanderthals became extinct.
Evolutionary casualties or hardy survivors?
A growing body of evidence is challenging the long-held view that Neanderthals died out completely over 24,000 years ago, victims of an icy climate and competition from newly arrived modern man.
Serrated stone tools
and jewellery were found here alongside Neanderthal remains, but it remains unclear whether modern humans or Neanderthals created the artifacts.
Crude flint tools found at this site in southern France were made by Neanderthals but, until 35,000 years ago, tools made by Homo Sapiens were equally primitive.
OUT OF AFRICA
The prevailing theory is that Homo sapiens migrated from Africa into the Middle East over 90,000 years ago and pushed into Europe around 45,000 years ago.
SOURCES: HISTORY OF PHYSICAL ANTHROPOLOGY, ENCYCLOPEDIA OF HUMAN EVOLUTION AND PREHISTORY