I'm curious, what are the uppoer/lower bounds of permitted gentic change in a species? What happens when it reaches the maximum allowed changes in that species? Does some flag get set off that says, "Woah there! You can't have any less body hair than that!" Or, "You can't have teeth any sharper than that ... no meat-eating scavenging for you!" At what point do non-harmful mutations somehow get edited out as being too far beyond a (man-made) "species" delimiter?
I mean this to be a legitimate question ... I'm curious as to the answers ...
Not sure what you mean, but if the population of a single species gets seperated (say by geology -- earthquake or flood or something), and are seperated long enough with no cross-breeding, the seperated species often eventually change into two species.
This can be chance --- like, say if the population was 50% black and 50% white --- then the "event" (say flood with a new river) occurs, and you end up with a population that is 60% white on one side and 60% black on the other --- you'd generally get two distinct populations of black and white whatevers.
(They recently found a population of frogs where this happened that recently go re-mixed --- they generally don't cross breed, although physically very similar, apparently b/c cross-bred offspring are not very viable -- croaks being the only ready distinction)
Or, to use the more typical form of evolition, if one type of predator is one one side and not on the other, that population would start to pre-dispose whatever trait helped avoid that preditor (assuming any live, that is).
As far as "how far can they go" and not be the same species? (which I think is the question) --- the answer is, it depends.
The simplified definition of a species is usually: can they have viable children?
And the answer to that is: just depends on how far the DNA changes, on a case-by-case basis.
Well it works like this. First you decide you don't like the idea of one type of animal turning into another type. Then you decide to draw the line at species because...well because you have heard the word species and that sounds like it will do.
That's it - sorry