You could always ingest other bacteria that can digest and break down lactose and rely on probiotics to digest the lactose for you instead of having a gene. Th

You could always ingest other bacteria that can digest and break down lactose and rely on probiotics to digest the lactose for you instead of having a gene. That's what ruminents do anyways, you need a steady colony of these helpful bacteria or you lose the tolerance. While that seems troublesome, for many animals that's how metabolism works for their entire life.