Ice Ages Caused Decline and Even Extinction in Europe’s Hunter-Gatherer Populations

A large-scale study of fossil human teeth from Ice Age Europe reveals that climate change had a significant impact on prehistoric human populations. Using the largest dataset of human fossils from Ice Age Europe to date, an international research team has shown how hunter-gatherers coped with severe climatic changes between 47,000 and 7,000 years ago. The study, published in Science Advances, highlights how population sizes declined sharply during the coldest periods, and in some regions, such as Western Europe, Ice Age populations even faced extinction.

Getting to Grips With Ice Age Demography

The research, led by Dr. Hannes Rathmann from the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen, marks a significant breakthrough in understanding the demographic history of Ice Age Europeans. Traditional methods of analyzing ancient DNA have been hampered by the limited availability and poor preservation of fossils. To overcome these challenges, the research team developed a novel method based on a machine learning algorithm, which allowed them to analyze morphological traits in teeth, the hardest tissue in the human body and the most commonly preserved fossil element.

The dataset included dental data from 450 prehistoric humans from all over Europe, covering a period between 47,000 and 7,000 years ago. The researchers focused on morphological traits—such as the number and shape of crown cusps, ridge and groove patterns, and the presence or absence of wisdom teeth. These traits, which are heritable, enabled the team to trace genetic relationships among Ice Age populations without the need for well-preserved ancient DNA.

Three human skulls from the Hohlenstein-Stadel cave in Southern Germany, dated to about 8,500 years ago, likely belonging to a family: a man (left), a woman (right), and a child (middle). (Osteological Collection, University of Tübingen)

Climate Change and Population Decline

The study revealed that during the Middle Pleniglacial period (47,000 to 28,000 years ago), populations in Western and Eastern Europe were genetically well connected, as evidenced by similarities in stone tools, hunting weapons, and portable art found across regions. The open steppe landscapes of this period supported large herds of mammals, providing ample food for hunter-gatherer communities and facilitating population interlinking across Europe.

However, during the Late Pleniglacial period (28,000 to 14,700 years ago), this connectivity broke down. The researchers found no genetic connections between Western and Eastern Europe during this time, and both regions experienced significant population declines and a loss of genetic diversity.

This demographic collapse coincided with the Last Glacial Maximum, when ice sheets reached their greatest extent, covering much of northern and central Europe. The harsh climate led to a shift from steppe to tundra vegetation, severely affecting the habitats of prey animals and the hunter-gatherers who relied on them.

The study also uncovered evidence that populations in Western Europe went extinct during the transition from the Middle to the Late Pleniglacial, likely due to the deteriorating climate. These populations were eventually replaced by new groups migrating from Eastern Europe, highlighting the profound impact of climate change on human survival and migration patterns during the Ice Age.

Recolonization and Population Recovery

The press release explains, as the climate began to warm after the Late Pleniglacial period, glaciers retreated, and steppe and forest vegetation returned, creating more favorable conditions for human habitation. The study found that the previously isolated and diminished populations in Western and Eastern Europe began to grow again, with migration between regions resuming.

The research team’s use of a machine learning algorithm, dubbed Pheno-ABC, enabled them to reconstruct complex prehistoric demographic events using dental morphology data. This approach, which represents a significant advancement in the analysis of fossil skeletal morphology, allowed the researchers to identify the most likely demographic scenarios among many possibilities.

Lessons for the Future

The findings of this study provide important insights into the demographic history of Ice Age Europeans and underscore the profound impact that climate and environmental changes had on prehistoric human populations. As Dr. Rathmann concludes:

“We should urgently learn from our past if we want to address the complex environmental problems of the future.”

Top image: Artistic reconstruction of a hunter-gatherer group from the Ice Age.                Source: Tom Björklund/University of Tübingen

By Gary Manners