A large-scale study of fossil human teeth from Ice Age Europe reveals how climate change significantly shaped the demography of prehistoric humans. This groundbreaking research utilized the most extensive dataset of human fossils from Ice Age Europe, covering the period from 47,000 to 7,000 years ago. The study, published in the journal Science Advances on August 16, offers new insights into how hunter-gatherers adapted to the changing climate during the Ice Age.
The research, led by Dr. Hannes Rathmann from the Senckenberg Center for Human Evolution and Palaeoenvironment at the University of Tübingen, developed an innovative method to analyze the fossils. Collaborating with experts from the University of Tübingen, the University of Ferrara in Italy, and New York University, Rathmann’s team employed a machine learning algorithm to examine the demographic changes of Ice Age humans.
Around 45,000 years ago, modern humans first migrated to Europe during the last Ice Age, marking the start of the Upper Paleolithic era. Despite the harsh conditions, these early human groups managed to inhabit the continent continuously, even during the Last Glacial Maximum around 25,000 years ago, when glaciers covered much of northern and central Europe.
The study highlights the challenges faced by archaeologists in understanding the impact of climate change on prehistoric human populations. With limited fossils available and poor molecular preservation for ancient DNA analysis, it has been difficult to determine how climatic factors influenced migration, population growth, decline, and extinction. Dr. Rathmann notes, “Due to the limited number of fossils available and their often poor molecular preservation for ancient DNA analysis, it has been very difficult to draw conclusions about the impact of climatic factors on migration, population growth, decline, and extinction.”
To address this challenge, the researchers adopted a novel approach by analyzing teeth, the hardest tissue in the human body and the most common fossil skeletal element. The team compiled an extensive dataset of dental data from 450 prehistoric humans across Europe, spanning a period of 40,000 years.
By focusing on “morphological” tooth traits—such as the number and shape of crown cusps and ridge and groove patterns—the researchers were able to trace genetic relationships among Ice Age humans without relying on well-preserved DNA. Dr. Rathmann explains, “These traits are heritable, which means we can use them to trace genetic relationships among Ice Age humans without requiring well-preserved ancient DNA.”
One of the study’s most exciting aspects was the examination of historical photographs of fossils, including those lost or destroyed during World War II. By analyzing these images, the team could include important fossils in their research.
The findings reveal that from 47,000 to 28,000 years ago, populations in Western and Eastern Europe were genetically interconnected. This period, known as the Middle Pleniglacial, was characterized by open steppe landscapes that supported large herds of mammals, the primary food source for hunter-gatherers. These favorable conditions likely facilitated the interlinking of populations across Europe.
However, during the Late Pleniglacial period, between 28,000 and 14,700 years ago, the researchers found no genetic connections between Western and Eastern Europe. Both regions experienced a significant population decline, leading to a loss of genetic diversity. This drastic demographic change coincided with severe climate shifts, including the Last Glacial Maximum, when ice sheets covered vast areas of northern and central Europe.
The deteriorating climate caused a shift in vegetation from steppe to tundra, impacting the habitats of prey animals and the hunter-gatherers who relied on them. Dr. Beier notes, “Our results support the long-held theory that populations were not only driven southward by advancing ice sheets but also separated into largely isolated refugia with more favorable environmental conditions.”
One of the study’s remarkable discoveries is that populations in Western Europe went extinct during the transition from the Middle to Late Pleniglacial. They were later replaced by new groups migrating from Eastern Europe. As temperatures began to rise and glaciers retreated, steppe and forest vegetation returned, allowing previously abandoned areas to be recolonized. During this period, migration between Western and Eastern Europe resumed, and populations began to grow again.
The new method used in this study, known as Pheno-ABC, enabled the researchers to reconstruct complex prehistoric demographic events using morphological data. Dr. Maria Teresa Vizzari from the University of Ferrara, a co-first author of the study, explains, “Our new method—which is based on a machine learning algorithm we call Pheno-ABC—has enabled us for the first time to reconstruct complex prehistoric demographic events using morphological data.”
This pioneering analytical tool could revolutionize the analysis of fossil skeletal morphology, allowing researchers to identify the most likely demographic scenarios among many possibilities. The study’s findings provide crucial insights into the demographic history of Ice Age Europeans, emphasizing the profound impact of climate and environmental changes on prehistoric human populations.
Dr. Rathmann concludes, “Our study provides important insights into the demographic history of Ice Age Europeans and highlights the profound impact of climate and environmental changes on the lives of prehistoric humans. We should urgently learn from our past if we want to address the complex environmental problems of the future.”
Source: University of Tübingen