Hunter-gatherers
were absorbed into farming communities
A newly-published genetic study of
ancient DNA obtained from prehistoric human remains in Sweden has provided a
fresh insight into the transition to agriculture in Scandinavia.
The ability to obtain DNA from the
remains of prehistoric people has in recent years added a new dimension to the
long-running quest to understand the demographics of the transition from
hunter-gathering to farming in Neolithic Europe. Studies based on living
populations have been unable to provide definitive answers, as ancient genetic
signals are often blurred by far more recent events.
Researchers at Stockholm University
and Uppsala University obtained genetic material from the remains of six
hunter-gatherers and four farmers from the Scandinavian Neolithic, dating to
around 5,000 years ago, together with a late Mesolithic hunter-gatherer from
7,500 years ago. The samples were obtained from mainland Sweden and the Swedish
island of Gotland.
It was found that the genetic
diversity of the hunter-gatherers was far lower than that of the farmers and of
any present-day Eurasian populations, suggesting that their population sizes
were very small. Fluctuating climatic conditions and/or restricted carrying
capacities might have affected hunter-gatherer population sizes. It is also
possible that the genetic diversity of the hunter-gatherers never recovered
from population crashes occurring during the Last Glacial Maximum when European
populations were confined to a few ice-free refugia.
A significant finding was that the
hunter-gatherer and farming populations were genetically distinct from one
another, confirming the view that agriculture was spread across Europe by
migrating farmers, rather than by indigenous hunter-gatherers simply taking up
farming. In other words, it was farmers and not just farming that spread.
The researchers also found evidence
for genetic admixing between the hunter-gathering and farming communities – but
it was one way. Hunter-gatherers apparently married into the farming communities,
but not the other way round. Thus the expanding farming communities assimilated
indigenous hunter-gatherers.
The study, published in the journal
Science, is part of a
recently-launched initiative to investigate ancient human remains in
Scandinavia. Known as the Atlas project, it is being conducted by researchers
at Stockholm University and Uppsala University.
References:
1. Skoglund, P. et al.,
Genomic Diversity and Admixture Differs for Stone-Age Scandinavian Foragers and
Farmers. Science (2014).
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