Sounds/IS very messy, as I've said many times.
Trial and error. Most mutations meaningless or negative.
No 'design' in sight.
One need not have (Fallacy) two individuals to pass on a mutation, one can do it, as we see in many birth defects/diseases.
90% of humans are born with (now, due to Evolution of environment/diet/body/skull) counterproductive Wisdom teeth.
This would eventually have become 0% were it not for Modern dentistry because those with no longer need wisdom teeth could get infections and even die.
They were on their way out, however slowly.
Messy biz that evolution/NATURAL selection.
see ie,
Another Evidence of Evolution. Just part of an Overwhelming body of such. One rarely mentioned but very telling. Life can be traced to a continuum, with many creatures, including us, having anatomical vestiges of our evolutionary ancestors. An 'immaculate creation' event wouldn't leave useless...
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