>>475985Species don't just suddenly pop up out of another species. Entire populations, which can be huge in number, will slowly change over time and eventually there's enough of a distinction that humans might stumble across them and go "Wow, two different species!"
You can get small populations which are separated from the main population which then go by this same process yeah, but many populations will not. What about shoaling fish? Populations of fish numbering in the millions, or even hundreds of millions, are a clear case where you might get 1.2 million fish cut off from the rest of the population and then they will evolve separately to the main population they were once a part of.
Have you ever heard of minimum viable population? It's the minimum number of individuals of a species required for the species to continue, not dwindle to nothing; a population where the death rate does not exceed the birth rate. Yes, you can get species starting as a small number but that's a pretty subjective word. What's small? 100? 1,000,000? Depends on the animal, mostly. For fish, especially shoaling fish, I'd say that 'small' is much bigger than you think it is and it is very reasonable to suggest that we might drop a species' number below the MVP line.
>we could repopulate the fucking planet with rabbits from 1 matting couple if we wanted.And then they'd become a bottleneck species, fraught with problems. Look at cheetahs, who are also a bottleneck species. This means their gene pool, as a species, is reduced and they are much more susceptible to being killed off by a disease. As well as this, any genetic defections that the original mating couple had? Maybe they're more susceptible to cancer or maybe their hips aren't quite the right shape. That's going to be seen in the entire population created afterwards. And sure, we could create lots of rabbits from just two... but that's ideal conditions. How about you put them in the woods?
