Thank you to Silas and Nosy Ned. I see that evolution is happening now and I'm OK with that. Silas, yes I see that we follow the evidence. I learned from talk origins about all the changes over so many millions of years. The two heads is just an example. I can't think of what we would evolve next so I used that example.
Yes Nosy Ned that was my question. So there is no rule. So see, this is my question. We can be basically the same for a very long time and then there's this mutation. An important one. One that gives a good advantage. I can see that the basic body plan is the same for all of the animals. Even for the whale.
So someone can have webbed feet or whatever - this can happen in one generation - and then forever the webbed feet people swim better than the ones without.
Anyway thank you.