As David Reich explains in his recent book, genetic studies provide evidence for the westward spread into central Europe of the Yamnaya
people from the stepes of Central Asia about five thousand years ago. This event is credited with the introduction of Indo-European languages. But exactly how the Yamnaya spread is uncertain. New Scientist has an interesting article on this by Colin Barras, with a rather sensationalist reference to the Yamnaya as ‘the most murderous people’.
Drawing largely on work by the archaeologist Kristian Kristiansen, Barras suggests that the arrival of the Yamnaya was a violent affair. The existing populations were already shrinking by this time, possibly as a result of epidemics of plague. The Yamnaya were probably physically stronger than the indigenous people and were more warlike. There is also a suggestion that they were mostly male.
This scenario reminds me of a poem by Robert Graves, who was influenced by the theory that an earlier matriarchal society had been replaced by a patriarchal one.
Swordsman of the narrow lips
Narrow hips and murderous mind
Fenced with chariots and ships,
By your joculators hailed
The mailed wonder of mankind,
Far to westward you have sailed.
As Barras remarks, these ideas are quite new and are based on evidence from only a few sites. But at present it seems likely that “the steppes migrants were largely male and violent”. This idea is supported bu a finding that mitochondrial DNA, which is maternally inherited, changedrelatively little at this time, while the paternally-inhrited Y-chomosome changed a great deal.