quote:
Rather, the first question I have in mind runs as follows: if a great many mutations fail (whatever the percentage of disadvantageous mutations, it is still, I presume, rather high, or at least it was at the beginning of evolutionary history), then would we not expect to find a high degree of examples of these failures in the fossil and skeletal records?
It is always a good idea to clarify the question, and see what it means. For a start, we are obviously talking about phenotypic rather than genetic variations - simply because the latter are not visible in the fossil record. That in itself makes quite a difference.
So, what we are looking for is mutations that would be seen in fossils, that would be obvious as mutations, and can be identified as "failures". (And the question of what it means to be a "failure" is also of interest - how long can it persist, and in how many individuals ? And given the sparseness of the fossil record how can we tell if a particular variation falls below the threshold ?)
Remembering that the fossil record is a sampling of life, we would expect such mutations to be as common in the fossil record as they are in living populations.
(Note that we would expect the biggest failures to be rare because they would not be passed on - the more successful a variation the more likely it is to be found)
So, at this stage I will turn the question around. Since you, presumably, have a decent idea of your criteria for "failure" how common are failed mutations in living or historic populations ? What proportion would be visible in a fossil ?