[Ruy Dias de Bivar]

And just how did they do that as the offspring would be sterile just as a horse and donkey can breed but the offspring mule is sterile. Same for other species.

[PapaBear3625]

And just how did they do that as the offspring would be sterile just as a horse and donkey can breed but the offspring mule is sterile. Same for other species.

If two "species" can inter-breed, then they are not distinct species, but rather just different races or breeds.

Consider canines. The various dog breeds can look very different from each other, with different temperaments and levels of intelligence, but still produce viable offspring with each other.

[FrogMom]

And just how did they do that as the offspring would be sterile just as a horse and donkey can breed but the offspring mule is sterile. Same for other species.

The offspring weren't sterile, or there'd be none of their DNA around today.

[JimRed]

And just how did they do that as the offspring would be sterile just as a horse and donkey can breed but the offspring mule is sterile. Same for other species.

Less differentiation, perhaps. Enough to detect, not enough to affect. Kind'a like negroid, oriental and caucasian are detectably distinct, but their interbreeding is not affected. If the human race is around in half-a-billion years we'll probably all be a pleasant shade of beige.