Mega study explored: This is why genes influence our diseases

Immigration was and still is very important

Willerslev’s team found that the genomes of modern-day Europeans were influenced by three major waves of migration. The first humans, Stone Age hunters and gatherers, migrated from Africa to Europe 45,000 years ago. A second migration of farmers occurred 11,000 years ago from the Middle East and Anatolia (present-day Turkey, Iraq and Syria). They settled mainly in southern Europe. And 5000 years ago, shepherds from the Black Sea region and the Eurasian steppes (modern-day Ukraine, southern Russia and Kazakhstan) came to northern and eastern Europe.

With each wave of migration, people brought certain gene variants to Europe. For example, cattle breeders in Eurasia were taller than people living in Europe at the time; this was probably because larger body sizes brought evolutionary advantages and their diet allowed for greater growth overall.

Larger northern Europeans, smaller southern Europeans

Since shepherds settled mainly in the north of the continent (e.g. Scandinavia), the people there are now even more numerous than in the rest of Europe. Originally from the Middle East, farmers in Southern Europe lived under different evolutionary conditions. Their diets were different and height did not seem to be an advantage, so they were shorter. That’s why people in today’s Italy, Spain or Greece are smaller than those in Central and Northern Europe.

Regions that remained isolated for long periods of time, settled long-term by neither Middle Eastern farmers nor Eurasian herders, now show the greatest genetic similarity to Stone Age hunter-gatherers. According to Willerslev, this situation particularly affects Eastern Europe. This is why the incidence of modern civilization diseases such as Alzheimer’s or type 2 diabetes is higher today than in the rest of Europe. Researchers suspect this is due to Stone Age gene variations that may be less responsive to modern diseases.

Origins of multiple sclerosis explained

One finding of the research team is particularly revealing: Willerslev showed a link between human DNA there and the spread of multiple sclerosis (MS) in Northern Europe. Today, MS primarily manifests itself with an overreaction of the immune system, which leads to the destruction of the nervous system. Such an overreaction of the immune system may have been necessary for survival in the past, especially among Eurasian shepherds. 5,000 years ago, this overreaction led to a strengthened immune system and thus better protection against diseases from shepherds’ sheep and cattle.

Today this protection is unnecessary. What remains is a genetically determined overreaction of the immune system. And with this, the risk of developing MS also increases. This is almost twice as much in Northern Europe as in Southern Europe. Precisely because pastoralists with the corresponding gene variant settled in Northern Europe. According to the researchers, this finding takes us a big step forward in understanding the development of MS and other autoimmune diseases.