Posted on Saturday, January 24, 2004 - 5:53 am:

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Big chill killed off the Neanderthals

It is possibly the longest-running murder mystery of them all. What, or even who, killed humankind's nearest relatives, the Neanderthals who once roamed Europe before dying out almost 30,000 years ago?

Suspects have ranged from the climate to humans themselves, and the mystery has deeply divided experts. Now 30 scientists have come together to publish the most definitive answer yet to this enigma.

They say Neanderthals simply did not have the technological know-how to survive the increasingly harsh winters. And intriguingly, rather than being Neanderthal killers, the original human settlers of Europe almost suffered the same fate.

Led by Tjeerd van Andel of the University of Cambridge, a team of archaeologists, anthropologists, geologists and climate modellers have compiled a vast new set of biological, environmental and social evidence on life between 20,000 and 40,000 years ago.

It includes data from sediment cores and 400 or so archaeological sites, and information gleaned from fossil bones and stone tools. To this they have added the most up-to-date climate models, and radiometric dates of human and Neanderthal sites and artefacts.

The result is a definitive series of maps covering climate change over time, the appearance of animal and plant populations, and how human and Neanderthal communities migrated with the seasons. The resolution is so good that, for the first time, researchers can reliably trace the movements of both hominid species.

Ice cores recovered from Greenland in the 1970s show that Europe's climate varied hugely during the last ice age, especially in the period between 70,000 and 20,000 years ago. Cold glacial periods were punctuated by warmer times, and the average temperature could rise and fall several degrees within a decade or so.

Studies of permafrost patterns, the remains of small animals and pollen grains, as well as fossil bones, show that such changes had a dramatic effect on the flora and fauna of the time, including Homo sapiens and Neanderthals.

The maps show that, facing temperatures that plummeted to -10°C in winter (see map), Neanderthals retreated south from northern Europe 30,000 years ago, a migration which coincided exactly with the southern march of the ice sheets (Neanderthal and Modern Humans in the European Landscape of the Last Glaciation: Archaeological Results of the Stage 3 Project).

It is surprising "the extent to which Neanderthals seem to have been deterred by the cold, and retreated as the going got tough," says archaeologist William Davies, a co-editor of the report based at University of Southampton, UK.


The maps also reveal that the earliest modern humans, the Aurignacian people, who appeared around 40,000 years ago, could not cope with the glacial cold either. They retreated south until 25,000 years ago when they were reduced to a few refuges, such as southwest France and the shores of the Black Sea.

The new maps show that even at the height of the last glacial period, 18,000 to around 22,000 years ago, continental Europe supported extensive grasslands which were fodder for huge numbers of migrant animals such as reindeer and bison.

The archaeological evidence strongly suggests that both hominids coexisted in southern Europe for thousands of years, but competed for ever diminishing resources. And that might have been the end for both Homo sapiens and Neanderthals but for the arrival of the technologically advanced Gravettians.

The Gravettians appeared in eastern Europe 29,000 to 30,000 years ago complete with flash new tools, such as javelin-like throwing spears and fishing nets, which allowed them to catch a greater range of prey.

They also had clothing to keep the cold out, such as sewn furs and woven textiles, and possibly more specialised social structures. Their ability to tough out the colder climes dominating Europe 18,000 to 25,000 years ago revitalised the human population.

The Neanderthals, however, without either new blood or new technology, found it impossible to survive and died out, probably around 28,000 years ago.

For Neanderthal expert Paul Pettitt of the University of Sheffield, UK, the evidence that climate adversely affected the Aurignacian people as much as the Neanderthals is fascinating. When the going got tough in northern Europe, says Pettitt, both adopted a "get out of the kitchen strategy".

In contrast, Gravettians used their technological prowess "to reorganise the way the kitchen was used". Pettitt says that step was just as revolutionary as becoming modern Homo sapiens in the first place.

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Posted on Friday, September 10, 2004 - 2:14 pm:

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Guatelli-Steinberg has spent the last decade investigating tiny defects -- linear enamel hypoplasia -- in tooth enamel from primates, modern and early humans. These defects serve as markers of periods during early childhood when food was scarce and nutrition was low.

These tiny horizontal lines and grooves in tooth enamel form when the body faces either a systemic illness or a severely deficient diet. In essence, they are reminders of times when the body’s normal process of forming tooth enamel during childhood simply shut down for a period of time.

“Looking at these fossilized teeth, you can easily see these defects that showed Neanderthals periodically struggled nutritionally,” she said. “But I wanted to know if that struggle was any harder than that of more modern humans.”

To find that answer, she turned to two collections of skeletal remains: One was a collection of Neanderthal skulls at least 40,000 years old from various sites across Europe; the other was a set of remains of Inuit Eskimos from Point Hope, Alaska. The Inuit remains, some 2,500 years old, are maintained by the American Museum of Natural History in New York.

She microscopically examined teeth from the Neanderthal skulls for signs of linear enamel hypoplasia, as well as other normal growth increments in teeth called perikymata, and compared their prevalence with those from the Inuit skulls.

“The evidence shows that Neanderthals were no worse off than the Inuit who lived in equally harsh environmental conditions,” she said, despite the fact that the Inuit use more advanced technology.

“It is somewhat startling that Neanderthals weren’t suffering as badly as people had thought, relative to a modern human group (the Inuits).”

Guatelli-Steinberg’s examination of perikymata offered snapshots of Neanderthal survival. Smaller than the linear enamel hypoplasia, perikymata are even tinier horizontal lines on the teeth surface. Each one represents about eight days of enamel growth so by counting their number, researchers can gauge the speed of tooth development – more perikymata mean slower growth of the tooth surface.

Guatelli-Steinberg counted perikymata within linear enamel hypoplasias, and was able to gauge how long these episodes of physiological stress lasted. The perikymata showed that periods of up to three months of starvation for both the Neanderthals and the Inuit were not uncommon. In fact, Guatelli-Steinberg found that Inuit teeth showed significantly more perikymata than did the Neanderthals, suggesting that the Inuit experienced stress episodes that lasted slightly longer than did those of the Neanderthals. She is looking ahead to do a similar comparison of tooth defects among the European Cro-Magnon who thrived after the Neanderthals disappeared. Coupled with the results of this project, and that of earlier work with non-human primates, she hopes to improve researchers’ understanding of just what information these tooth defects might reveal.

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