absolutely not, I'd say this is an extremely common flaw in our 'anticipatory' logic that computer modelling exposes
a rabbit could be born with a mutation that grants rabbit superpowers; could run twice as fast, jump twice as high- and still die of disease before reaching sexual maturity and passing that mutation on.
the Darwinian algorithm cares not a jot if it wasted a great advantage- it has no goal to improve the species.
In the context of evolution, which is a population-level multi-generation process, we talk about the general case of individuals that reproduce. If an individual doesn't reproduce, their heritable mutations are irrelevant, and those individuals themselves are generally only significant in those species where they have explicit roles (e.g. eusocial insects with sterile worker castes).
preserved, but in the wild most genetic lines die out regardless- so what mechanism would be preserving this small advantage meanwhile if natural selection has not had time to pay off yet?
If a mutation provides an advantage, it means that it makes the associated genes more likely to persist and propagate through the population. If the advantage is very slight, the genes of that individual and its offspring have only a very slightly better chance of persisting and propagating through the population than those of an average member of the population.
If you have an example an advantageous mutation where natural selection has 'not had time to pay off', please describe it to clarify what you had in mind.
there's the catch 22, significant advantages are extremely hard to come by accidentally, and insignificant advantages are simply.. insignificant. meanwhile of course the vast majority are deleterious
Not really. It depends on the species and how you count the mutations. The more deleterious the mutation, the less chance it has of being propagated - many are lethal during development, so are not seen even in immature individuals; the remainder will be selected out over subsequent generations. The majority of accumulated mutations are likely to be effectively neutral at any given time (having been either historically neutral or beneficial, and now fixed) the few novel advantageous mutations will tend to propagate to fixation, and the novel neutral mutations will tend to drift.
However, that is an overly simplistic description, the mutation-selection balance is complicated by genetic drift and the tendency for persistence & accumulation of deleterious recessive mutations, n other considerations.
A mutation that has an 'insignificant advantage' is neutral. A mutation is beneficial if it provides a selection advantage, i.e. it is significant. Beneficial mutations are
relatively rare, but frequent enough to enable rapid and significant changes under strong selection - selective breeding is an excellent example; in a few thousand years we've changed our agricultural flora and fauna beyond recognition by strong selection of natural variants.
this matches what we see in the fossil record - very little evidence of any gradual improvement occurring over time
It is not a case of 'improvement' over evolutionary timescales. Evolutionary adaptation responds to changing environmental conditions; what is successful in some conditions is less so in others. But the more fossil discoveries that are made, the clearer the lineages and their relationships become. We don't have many detailed examples of rapid diversification or change because of the limitations of the fossil record, but what we have is conclusive enough that we can predict the location of and time period of strata where we expect to find transitional fossils of a particular clade - and find them.
