Not really. A genetic defect is a precursor to evolution. If the trait doesn’t benefit the animal and isn’t passed on with reproduction there is no evolutionary process, just a dead mutant.
That what you described is part of the evolutionary proces, just because it doesn't last doesn't mean it is not part of the proces. Failures breed succes.
This isn't that, though. If this chick lived long enough to breed, it would not have four-legged offspring. This is a defect, likely from birth. Evolution doesn't happen with a single generation. Millions of years of variations made genetics diverge. Not random mutations of extra limbs.
This is like throwing a book in a fire and saying it's part of the cooking process. Just because it has some of the same aspects, doesn't make it the same thing.
You're thinking about multiple kinds of evolution. Evolution operates all the time, and does not need millions of years or even thousands of years. It also doesn't need to make a population more traditionally "fit". We saw an evolution within humans in Africa recently after people having the bad trait of sickle cell anemia gave them higher rates of survival due to the external force of Malaria, leading to more people in the population having sickle cell anemia from birth. This is usually considered a bad change anywhere else in the world, but this is a rapid evolutionary shift that has lead to worse health overall for the population. Still evolution.
Too many people keep comparing evolution to a refined process e.g cooking, someone else said painting the mona lisa, but it's not like that all of the time. Also see: defects in dogs being passed on rapidly due to cuteness to humans that would otherwise make 'strong' dogs easy prey 99% of the time in the wild.
It is only a defect because of your judgement. It is a mutation and mutations are a part of evolution.
If this chick bred, it might have four limbed offspring or maybe it just raises the chance of mutations of this kind by some percentage in any offspring down the line. You might not see another mutation for many generations. That doesn't mean that there is no evolution going on.
It is about the genes not about the individual looks or characteristics of one animal.
If this isn't detrimental to the survival of the genes then it will most likely stay in the genepoool. If the environment changes or the mutations add up to something that makes this benefitial for survival (of the offspring) then it might become a new variation or even a new species over time.
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u/Lou_LL_11 29d ago
Genetic defect is just another word for evolution.