Ancient DNA shows first farming impacts
An international research project featuring Australian experts says the introduction of agriculture may have changed the DNA of ancient humans.
When agriculture emerged in Europe about 8,500 years ago it not only changed the very way that people lived, but may also have modified their DNA, according to the report published in the journal Nature.
The study used advanced DNA-mapping techniques to look at the relationships between complex genetic traits from samples of people who lived ages apart.
The researchers say they have found the direct results of adaptation to changing diets, environments, disease-causing organisms, social organisation in the DNA of ancient European farmers.
The report includes evidence of natural selection on specific locations on DNA related to milk digestion, pigmentation and disease immunity.
Indirect evidence of this adaption can be detected in the patterns of genetic variation in today’s populations, the study shows, but modern genomes are “just echoes” of the past and cannot directly be connected to specific events.
But now, the experts say, the study of ancient human DNA makes it possible to watch how natural selection happened in real-time.
“We’ve been able to take advantage of improved DNA extraction techniques and the largest collection of genome-wide datasets from ancient human remains. This has allowed us to identify specific genes that changed during and after transition from hunting and gathering to farming in Europe,” says co-author Professor Alan Cooper, Director of the University of Adelaide’s Australian Centre for Ancient DNA (ACAD).
The DNA came from the remains of 230 ancient individuals who lived between 3,000 and 8,500 years ago at different sites across what is now Europe, Siberia and Turkey.
A comparison of the ancient genomes to one another and to those of present-day Europeans revealed 12 positions on the genome where natural selection related to the introduction of farming appears to have happened.
Many of these changes (variants) occurred on genes that have been associated with fatty acid metabolism, vitamin D levels, light skin pigmentation and light eye colour, which are important given the decreasing exposure to sunlight in northern latitudes.
Two variants appear on genes that have been linked to higher risk of coeliac disease, but that may have been important in adapting to an early agricultural diet.
Other variants were located on immune-associated genes.
“The Neolithic period involved an increase in population density, with people living close to one another and to domesticated animals,” says Dr Wolfgang Haak, from the Max Planck Institute for the Science of Human History in Germany.
“Although that did not come fully as a surprise, it’s great to see it confirmed in ‘real-time’.”
Being able to look at numerous positions across the genome also allowed the team to examine complex traits for the first time in ancient DNA, showing the evolution of height across time.
“Some of these traits have been studied before,” says Harvard Medical School’s Professor David Reich, one of the senior authors.
“This work with ancient DNA enriches our understanding of those traits and when they appeared.”