that hadn't evolved both genders would die out,
I see that we are back to the basics. A new species does not just jump one day it is a horse, the next child is a donkey. It's a matter of changes adapting to the environement. A horse would not change if it is in the family of many other horses, instead it becomes isolated, because it (and some small herd) crossed a mountain that had never before been crossed, or the continents drifted apart, or certain circumstances that can effect reproduction.
(Just-So story)
The new herd, with both genders, now lives and breeds in isolation from the ancestral herd. Over time the chromosomes change such that they can no longer breed with the original stock. Through the adaptations of survival in their new habitat they may take on characteristics different, but not too different, from the original population.
Many potential new species die with a single member.
TP |
