You are reporting the following comment to the PledgeBank team:
All life originated as you know from simple organisms, and because of this simplicity, mutations were much easier.
Simple life became more and more complex, until species started to become divided into specified groups. These differences in species made the definite divisions that determined which types can compatibly breed with each other. Splitting the groups of species in this way ensured that no further change of that species was possible. Humans are not compatible with any other species for mating purposes, and that ensures we remain totally human, this goes for all other animals of a specific type.
It is at a very early stage of all lifes evolution that changes occur, and once all possible mutations have occurred it is up to each type of life to strive for its own survival. Only superficial adaptations and learned skills are possible once the species has been determined and developed fully. Breeding also alters species somewhat, and hybrids often occur within a single species.
When a species is successful at survival, it remains. When it is not successful it becomes extinct.catherine souter, 12 years ago.