Haplogroup distribution in Europe began approximately 33,000 BC with the influx of haplogroup IJ from the Middle East. After around 10,000 years, mutations caused the creation of the distinctly European haplogroup I. Most scientists believe that the Cro-Magnon populations belonged to this genetic group. This division is still predominantly located in Northern Europe, particularly Scandinavia.
One of the most common population groups in Europe is haplogroup J. It descended from Mesopotamia into the areas of Greece, Italy, France and Spain sometime during the Bronze Age.
The last influx of genetic variations from Africa occurred sometime after 7,000 BC. Haplogroup E1b1b migrated from the Horn of Africa 25,000 years ago and ultimately made its way through the Middle East and into Europe, settling in Greece and the Balkans.
Haplogroup G descended into Europe from the Caucuses, primarily responsible for genetic variations found in the Russian and Eastern Europe regions. A mutation of the haplogroup, G2a, however, is found in Switzerland, Greece and Italy. A number of theories exist as to why this gene came to Europe, most notably the use of eastern populations as fighters for the Roman Empire. This is supported by the fact that haplogroup G is less prevalent the further away one gets from Rome.