[nerevarthelame]

You're right that they should present the evidence, but "How many millions of years" isn't an especially convincing counterargument either. For most of those millions of years, mammals have been drinking strictly the milk from their species only during their infancy.

[bluGill]

About 1/3rd of adult humans have genetic mutations to make drinking milk safe. (by coincidence most of those adults speak English). Because of that adaptation the other species argument is invalid.