Chromosomes.

Apes have a greater number of chromosomes than does man. This is the principal reason why a dog may be crossed with a wolf, a lion with a tiger, a donkey with a zebra. There is a chromosome match which does not occur between man and ape in the natural world. So if apes and humans are unable to interbreed, it seems highly improbable to me that X million years ago man descended from apes.