Most people are lactose intolerant as adults, but nearly everyone produces sufficient lactase as an infant. however, in some cases, genetic mutations can occur that make an infant lactose intolerant. from an evolutionary perspective -- over thousands of years -- why would lactose intolerance in infants be very rare in the population?

Lactose intolerance in infants is very rare in the population.

 This is because lactose intolerant in infants cannot digest breast milk and therefore it dies.
 They don't have a chance to pass the mutation on to their children.

Lactose is found in dairy items like yogurt and drain. In today's life, lactose intolerance in infants is more common in the population because today there are alternatives to breast milk.
For example, Soy milk, and lactose-free formula. Therefore lactose intolerant in infants can survive.

Grape jelly so a y did you ask this question