A minor hobby of mine is to collect examples (or possible examples) of gene-culture coevolution.
Here are a few for the collection (inspired by an interview with Joseph Henrich at edge.org)
Some early examples:
1-Brains expanded (genes) which enabled learning and accumulation of ideas (culture) which selected for larger brains (genes)
2-Use of tools (culture) selected for manual dexterity (genes) to throw objects (seemingly selected for in males more strongly) or to thread a needle (selected more strongly in females?) which allowed for more use of tools .
3-Fire and cooking (culture) selected for smaller stomachs, less robust teeth, shorter intestines (genes)
Some more speculative later ones:
4-Cultural evolution created cultural prestige: the status that arises from being admired for having knowledge or a skill. Did cultural evolution (culture) selects for cultural prestige (genes)?
5-Agriculture made possible population growth. Did agriculture (culture) select for groups that could scale-up, expand without fracturing, that is groups that were cooperative and high-trust among strangers (genes)?
6-Did moralistic religions (culture) select for greater cooperativeness and trust of strangers (genes)?
7-Did polygyny (culture) select for more competitive risk-taking males (genes)?