 Purred: Tue May 10, '11 10:53pm PST |
 | |  | | Buddy: actually, the shape of an animal's teeth can evolve over time. 
This may have already been said, but didn't have time to do more than skim...
Evolution doesn't only take place over the course of thousands of years -- you can see it in action with fruit flies (a favorite test subject for scientists studying evolution given their short life span) and bacteria.
Some of the factors that influence how quickly it happens are the strength of the environmental pressure and how quickly the organism in question reproduces.
With cats specifically, females begin producing in their first year or life, tend to go into estrus in the spring (so generally one litter a year), and the African Wild Cat (the closest relative of the domestic cat) lives an average of 12-15 years.
One can view individual breeds as a form of evolution -- the environmental pressures to evolve were manmade, and the "natural" selection was in fact human selection, but as far as the development of certain genetic traits and the extinction of others, that's happening right before our eyes as new breeds are created.
That said, changes in digestive tracts and tooth configuration take longer. Commercial catfood feeding wasn't widespread until after WWII, and even after that, there were still quite a few barn cats living off what they caught and interbreeding with more domesticated domestic cats. That's a mere eyeblink in evolutionary time -- I'm not sure that's enough time for major changes to how cats absorb nutrients, process carbs, or anything like that. Allergies, maybe.
But it's also worth noting that evolution isn't really being allowed to happen naturally with domesticated cats -- or at least it's pretty severely constrained, in that many of the cats who are best-positioned to survive to reproduce (those with happy homes, health care, protection from predators, and a steady supply of food) are the ones that we're spaying and neutering.
We are increasingly controlling which cats are allowed to reproduce, and -- since, increasingly, the cats allowed to reproduce are purebreds -- we're choosing which traits are selected for.
In natural selection, the traits that are selected are generally those that give organisms an advantage in surviving to reproduce. They may be traits that allow them to survive on less specialized food sources, that give them advantages in escaping from predators, etc.
We're not selecting for traits that have much to do with survival; we're selecting for coat length and eye color and ear size. There may be cats out there that have mutations that allow them to better process carbohydrates, or give them partial immunity to toxins, but those mutations are undetectable to us, and not likely to be linked to the sort of traits that we do select for, so whether any of the cats who have them are being allowed to reproduce (i.e. whether they're happening among purebreds or the other group most likely to reproduce -- ferals) is anyone's guess.
This isn't an argument against spaying and neutering, incidentally. But the fact that we're in essence creating our own evolutionary pressures to replace natural ones, and selecting for traits that don't have anything to do with nutrition, means that it's that much more imperative to feed cats a diet that corresponds to what we know about where their nature left their digestive systems before we took over their evolution. |  |  | |  |
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