WherruT o e in a nutshell is all down to sex/reproductionIf you...

Wherru
T o e in a nutshell is all down to sex/reproduction
If you are strong/smart/attractive enough to live until breeding age you get a shot, those that have attributes to support this will breed earlier faster and longer and eventually outnumber the weaker species
Throw in mutation for occassional rapid change

Thanks Goatskinner

I hope we get responses from those who think the the theory of evolution is a fairy tale so I can understand what they reject.