Knowledge of cultivation first entered Sweden about 6,000 years ago with people moving here from northern Europe.

In the Middle East, people had been farming and keeping livestock for about 10,000 years. In the area that is now Sweden, people still lived as hunters and gatherers.

"The knowledge spread surprisingly slowly from Central Europe and into the Nordic countries. Perhaps it finally came here because there was unbroken land to cultivate here, in combination with human curiosity," says Elin Fornander, doctor of archaeology.

Farmers settled

Agriculture allowed families to live in the same place instead of being on the move, which also led to them having significantly more children.

"A big difference between hunter and farmer is that the farmer can produce a surplus. Not only does this mean that you can save for a rainy day, but you can also help people around you. Peasant life requires much greater cooperation between different groups and therefore we also get a society that is perhaps more similar to the one we have today," says Björn Nilsson.

Immigration led to the population of southern Sweden doubling in just a few generations.

Lived segregated in the Stone Age

But it took a long time before the two groups of hunter-gatherers and farmers began to mix their populations. They did exchange objects with each other, but when the researchers look at the skeletons' DNA, they see that the two groups did not have children with each other at all, for about a thousand years.

"There are 40 generations, so there must have been very strong barriers to meeting and mixing," says Mattias Jakobsson, professor of genetics.

Watch the first episode of The History of Sweden on SVT Play or or 5/11 at 21 pm on SVT1.