This maintaining lactose digesting in adulthood gene spread through populations unconnected with whatever ‘culture’ this mutation first appeared in. You don’t speak that cultures language I bet. nor believe in their gods.

You confusing plasticity of behaviour with ‘culture’. The more an animal has to learn rather than have hardwired behaviour set ingenes then it’s more likely to play and explore new territories and behaviours and be able to take advantage of any benefit a mutation may allow.

Maintaining a culture is also outcome of our large human behavioural plasticity. But cultural practices do not go through a genetic bottleneck and cannot be selected for.

EG I can digest milk as an adult but my Y chromosome is that of the original hunter-gathers in Europe and not the johnny-come-lately farmer types and cattlemen who prob brought the milk digesting gene in.

Also while the population grew with that new ability to drink milk as well as eat cheese, the populatin splintered into various cultures we know in Europe today. The is no singular domniant milk-drinking culture continuing in a thousand year reich for example.

Not that I would run over a cow in India you understand, even if I was tempted by my hunter-gather culture genes.