And here's the problem - gametes are haploid and have a harder time repairing DNA damage than diploid cells due to having only one set of chromosomes (that's also the reason why radiation damage is more of a problem for females - oocytogenesis takes place just once in a female's life and then all the egg cells are held in a state of division in which they are very vulnerable to radiation damage).
Ah, but that's a different, although related, problem. I was treating sterility as the inability to produce gametes of any sort. For example if environmental radiation blocks spermatogenesis. As soon as fertilization takes place you are into the "is the zygote viable?" issue, which is obviously dependent on the amount of damage to the DNA and size and redundancy of the genome. There is a subtle difference between being completely sterile and simple never producing viable offspring. The from the outside it may appear the same, but in one case the probability of population survival is exactly 0 and in the other it is somewhere between 0 and 1, tending towards 0 as the amount damage increases.
... oocytogenesis takes place just once in a female's life and then all the egg cells are held in a state of division in which they are very vulnerable to radiation damage...
While ova are all produced at one time, they are better shielded from alpha and beta radiation than spermatozoa due to not swinging wild and free behind a few mm of skin and flesh.
Unfortunately, radiation presents a fairly catastrophic hazard to our reproductive system by the very nature of some basic principles of the latter
But at lowish levels it can promote rapid diversification in a population, by the same argument. Which will lead to increased survivability over time.
You probably can't "evolve" a means of not being sterile after being exposed to enough radiation. Just like you most likely cannot "evolve" a means of not being sterile after your reproductive organs have been smashed with a sledgehammer.
Really? Both of those are incredibly strong selection pressures, although I would imagine the first is more common than the second.
Provided the radiation does render the entire population sterile, then only those with a higher "resistance" of some form (eg. better cellular repair pathways, higher fission rate of cells to gametes, natural lead codpiece, whatever) can possibly reproduce. This would in some cases be passed down to their offspring. The next generation would therefore contain a much higher proportion of fertile individuals.
Equally the sledgehammer to the 'nads (if it became common enough) would promote individuals with methods to mitigate the damage (say, bony plates over them or, more likely, behaviours that don't lead to angering mentalists with hammers:)).
Non-universal catastrophic environmental damage to the reproduction mechanism is one of the fastest acting selectors in any form of natural selection. It can produce a rapid change in overall population fitness in a single generation.
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Ah, but that's a different, although related, problem. I was treating sterility as the inability to produce gametes of any sort. For example if environmental radiation blocks spermatogenesis. As soon as fertilization takes place you are into the "is the zygote viable?" issue, which is obviously dependent on the amount of damage to the DNA and size and redundancy of the genome. There is a subtle difference between being completely sterile and simple never producing viable offspring. The from the outside it may appear the same, but in one case the probability of population survival is exactly 0 and in the other it is somewhere between 0 and 1, tending towards 0 as the amount damage increases.
While ova are all produced at one time, they are better shielded from alpha and beta radiation than spermatozoa due to not swinging wild and free behind a few mm of skin and flesh.
But at lowish levels it can promote rapid diversification in a population, by the same argument. Which will lead to increased survivability over time.Really? Both of those are incredibly strong selection pressures, although I would imagine the first is more common than the second.
Provided the radiation does render the entire population sterile, then only those with a higher "resistance" of some form (eg. better cellular repair pathways, higher fission rate of cells to gametes, natural lead codpiece, whatever) can possibly reproduce. This would in some cases be passed down to their offspring. The next generation would therefore contain a much higher proportion of fertile individuals.
Equally the sledgehammer to the 'nads (if it became common enough) would promote individuals with methods to mitigate the damage (say, bony plates over them or, more likely, behaviours that don't lead to angering mentalists with hammers :)).
Non-universal catastrophic environmental damage to the reproduction mechanism is one of the fastest acting selectors in any form of natural selection. It can produce a rapid change in overall population fitness in a single generation.