Originally posted by JadeMantis
This would be micro-evolution. I don't think there is much debate over this. It is macro-evolution that is questioned by many. Perhaps once H5N1 evolves into a kind of bird we can talk again...
Peripheral isolates of any species is the thing to grasp if you actually do want to understand how new species arise. "Natura non facit saltum" was the classic dictum that nature does not make leaps implying a solely gradualistic mode for evolution.
We now know that macroevolutionary events appear to happen in an episodic pattern rather than this exclusively slow gradualistic pattern. The Cambrian explosion and the laying down of all the major body plans (bauplan) for the subsequent radiation of metazoans is a good example of a macroevolutionary event with just these properties. Climate crisis or catastrophism appears to wipe out large numbers of species leaving new niches to be exploited is a recurring theme in the story of how life evolved on this planet.
Gould and Eldredge's punctuated equilibrium model is often contrasted against the old Darwinian idea of phylectic gradualism but this is not a problem with the accepted fact that macroevolution has occurred merely a refinement of how these macroevolutionary events took place.
The creationists have of course seized on this to play to a scientifically uneducated crowd as catastrophism appears to atavistically feed into the psyche of these folk. Punctuated equilibrium was a development of Mayr's models of allopatric and sympatric speciation events where geographic isolation is crucial to how new species arise. Inbreeding and the accumulation of genes through consanguineous matings and the presence of rare alleles in new combinations very likely plays a major role in the genetics of how new species arise by deconstructing complex genotypes and regulatory/transcriptional networks unfurling new developmental programmes. This is very likely fatal in most instances but when selection favours a viable and reproducing entity by this mechanism it is destined to propagate further and on and on and over eons we begin to see how the original replicator of a self-replicating nucleic acid species could give rise to a sequoia, paramyxoviruses and apes all from a common ancestor in a unbroken ever branching tree.
A large interbreeding population has a homogenising effect however over geological deep time isolated populations can develop properties of "incipient species" and eventually become reproductively isolated and incapable of being homogenised back into the parental bauplan.
A wealth of evidence supports the "Out of Africa" model for human evolution. Educated people all accept evolution exists and we evolved from a primate-like ancestor. This is the greatest story humans know in my opinion. Again I go through life thinking science is how the heavens go and religion how to go heaven if that suits you. The essential thing is not to step on each others toes and Gould put this forward nicely in the concept of NOMA = Non-Overlapping MAgisteria.
Misrepresentations of this healthy, interesting and important debate on the origins of species by ill-informed creationists are not helpful.