[AndrewC]

Why waste resources making an enzyme (lactase) that would never be of any use?

So you are saying that lactase is of no use?

[allmendream]

My answer was not so lengthy that you needed to abridge it. It was clear from my context that lactase is only of no use to something without access to a ready supply of milk.

Most adult mammals will never get an opportunity to drink milk, so no, a lactase gene would be of no use.

To a nursing mammal it is of primary importance.

To a human with cattle it is a distinct advantage to have this mutation.

So much for the ‘no advantage to any change in DNA’ idiocy.