RE: How long does evoluution take.
November 25, 2018 at 4:41 pm
(This post was last modified: November 25, 2018 at 5:24 pm by Anomalocaris.)
(November 25, 2018 at 2:51 pm)Jörmungandr Wrote:(November 25, 2018 at 12:19 pm)Gawdzilla Sama Wrote: Evolution is based on the reproductive cycle of the creatures experiencing said evolution, right? Bacteria with a reproductive cycle of hours would experience more evolutionary chances in a year than, say, a grey whale.
I've been under that impression, but one thing stops me from embracing that explanation. Mutation rates are relatively constant, and not affected by rates of reproduction. So it doesn't seem as simple ultimately as more reproduction, more mutations (not saying that is your position, but that seems a logical way to interpret the relationship between reproductive frequency and mutations. Thinking about it now, I suspect the frequency of reproductive cycles likely simply amplifies differences in reproductive fitness, resulting in more efficient and therefore quicker selection, but I'm just spitballing).
The reason why rate of reproduction is important is only mutations that occurs in viable reproductive cells matter. A mutation that occur in your skin cell may give you skin cancer, but you can’t pass it on. So it doesn’t matter if you live a long life and develop a million mutation in other parts of your body during your life. None of them matter because if they were not in your egg cells, then you can not pass them onto your offspring. Your offspring will receive from you a set of relatively prestine genes without any of the mutations that happened elsewhere in your body.
So you might argue if you lived a long life, then your egg cells individually also has a long time in which to accumulate mutations. Well, not entirely true. Mutations do occur in a fully formed cell that’s just sitting there. But majority of the mutations in any cell occurs during cellular division, when the cell was first formed. In human females the egg cells form only once, before you were born, and then stored and rationed out for use during your entire life. So majority of the mutations you can possibly pass on to your offspring happens only once during your own embryo development. Hence, amount of evolution through mutation that originate with the female is closely correlated the number of generations of fetuses, and not closely related to how long each generation lives or how many years lapse between generations.
This is a somewhat different mechanism for evolution through mutations that originated with man. In man, unlike in woman, sperms are continuously produced through cell reproduction throughout the life of the man. So each generation of new sperm cells contain all the mutations the gem cells developed since the last generation of species cells, plus all the mutations the gem cells acquired during all the previous generation of species cells, in addition to errors that crept in when the sperm cell itself is produced. So as a man get older, his sperm cells also contain progressively more mutations that can be passed on.
So men, particularly fertile older men, are mutation machines for the purpose of reproduction and evolution, where as women tend to be genetically conservative for the purpose of reproduction and evolution, even though men and women accumulate mutations in other cells of their bodies at identical rates.
Another thing about the common colloquial image of evolution is if you develop a mutation that is beneficial to you then you have a higher chance of passing it on to your offspring’s.
Absolutely false.
The only mutation that develops in you that you can pass on has to be in your reproductive cells. Changes to the genome of your reproductive cells has zero possibility of affecting your personal chances of survival. The genome of your reproductive cells cannot affect any of your physical traits.
What mutations in your reproductive cells will do is to pass the mutation and cause it to express itself not in you but your offspring‘s. So it is upon your offspring‘s that survival of the fittest acts upon the consequences of the mutations that occurred in you.