[Soliton]

Silliness. If we lock a bunch of people up in a dark cave and their eyes begin to adapt to the dark so that they see better in the dark does that mean they're a new species? It's like saying that blacks and whites are different species because of pigment adaptation in skin.

No it is like saying black prople can't see white people and white people can't see blck people so there is no interbreeding between the two. Once two populations stop interbreeding, the first step of the speciation process has begun. Imagine that all of the dogs in the world except Great Danes and teacup chihuahuas remained. It would be chemically possible for them to interbreed, but virtually impossible for them to mechanically interbreed. Their differences in size speed and strength would place different evolutionary selection pressures on the two populations. The little dogs might evolve to be smaller to adopt a stealth lifestyle. They may become nocturnal. The big dogs may become under pressure to become bigger to access larger prey. Who knows? The separation of the two through sexual selection is the first fork in the road with many forks ahead.

[raygunfan]

but the black humans remain humans, the white remain white humans, and the dogs remain dogs...

LIKE IN THE BEGINNING....LIKE TOMORROW....

[DouglasKC]

Once two populations stop interbreeding, the first step of the speciation process has begun. Imagine that all of the dogs in the world except Great Danes and teacup chihuahuas remained. It would be chemically possible for them to interbreed, but virtually impossible for them to mechanically interbreed.

Your argument is filled with a lot of supposition and fortunate circumstances none of which can really be debated. I say that the fish will eventually breed and can never become different species.