Jedi Council Member
One thing we discussed during a break in the session was the idea that new species might appear simply be being born to existing mothers. Essentially, one species would give birth to another species, due to an influence similar to that that produces viruses and the first cell(s). In this case, either the mother, or the zygote perhaps, would incorporate the eternal object, or thought-form, of the new, desired species into its own being, rearranging its DNA to bring a new form into existence.
As it happened 300,000 years ago when humanity incarnated in the third density ... seeking to experience a more physical reality.