Thank you for your last two posts these are very enlightening and show me that I can't generalize about environmental influence on speciation.
A good example would be found in the aquatic ape hypothesis of Sir Alister Hardy. These apes separated from the savannah-type apes and followed fresh river water and its food sources to the ocean where they found year round food.
This isolation from their group speciated them. The seafood they ate benefited the developement of the brain. And the bouyancy of the ocean led them to stand upright... as well as lose body hair and develop a nose more efficent for keeping out water while swimming in it.
Not much to do with instant mutation. But imagine the gradual mutations taking place over, say, a million years while these bi-pods hung-out on the beach!
I'm glad this theory has gained some acceptance in the real world since it pretty well answers every question to do with our evolution, adaptation and appearance. The nay-sayers are, for the most part, closet "creationists" who possess a dash of "intelligent design" for good measure.
The Aquatic Ape idea also holds the potential to become the "missing link". This is because the only evidence of this species would be their descendents. They're personal remains are no longer available... having been mostly washed out to sea or eaten by seagulls and Orcas.