It’s enticing but usually pretty dumb to entitle anything The X Gene, like I just did, because genetics generally work more according to statistically complex interminglings of multiple causal factors.
But Razib Khan has a blog post about the skin color gene SLC24A5. Much of the world’s population, both African and East Asian, has the ancestral darker version, while Caucasians in Europe and the Middle East tend to almost all have the new lighter version. South Asians fall in-between.
It’s hardly the only gene contributing to what we recognize as racial differences between Caucasians and others, but it’s rather striking.
Here are percentages of the old dark version by group (note, some are based on small sample sizes so don’t get too worked up over small differences):
Samaritans, whether Good, Bad, or Ugly, live on a couple of hills in Israel.
The Basque live on the coast of Spain and France and speak a pre-Indo-European language isolate.
The Burusho or Hunza (zero percent in sample of 25 people) are a North Pakistani mountain tribe who speak a pre-Aryan language isolate.
First Indian prime minister Nehru was a Pandit Brahmin from Kashmir in the far north of the Subcontinent.
The Mbuti are a Pygmy people.