Not my field, but I don't think it's even possible to really pinpoint "the" most recent evolutionary step, not to mention being able to define "step" in an incredibly slow variable with multiple layers of continuity (individual, population, and whole species levels).

But I would say that it is very recent for sure, as lactase persistence is a trait that really only started (above "noise" level stochastic mutations in the population) when we started using dairy some 6000 years ago because of selection pressure.