Why aren’t people with beneficial versions of these traits aging less, living longer, and having more children?
Even if people with less active transposons have slightly more children that’s only one part of the evolutionary equation.
The frame I was taught is evolution= natural selection + mutation + gene drift. Mutations are a force for increased transposon count (and if there’s more DNA repair there are less mutations). Natural selection is a force for decreased transposon count. You would expect those two forces to find an equilibrium so that the amount of transposons isn’t a problem at the age where an animal bears children. If you have very effecitve germline transposon suppression transposon also evolve to escape the transposon suppression.
When it comes to DNA repair I would expect that it’s simply a cost for a cell to put resources into DNA repair.
more vigilant germline transposon suppression
Without evolutionary pressure that prevents individuals with more active transposon to reproduce less that just gets the transposons to express themselves more and you have +/- zero.
Sure, but wouldn’t a hunter that stayed physically 25 until the age of 45 have a higher inclusive genetic fitness, all else being equal? (edit circa 2022-07-02: Wow, I was dumb. Red Queen hypothesis, baby.)
All else isn’t equal. Transposons replicate. That’s what transposons are about.
The genetic fitness of the hunter doesn’t really matter (that’s basically the insight Dawkins wrote about in the selfish gene). You have to look at the fitness of the transposon and what’s good for the transposon.
If a transposon copies itself into another chromosome it can increase the chance of being inherited to a child from 50% to 100%. That’s highly useful to the fitness of the transposon and worth slightly reduced lifespan of the child.
Both of those forces are at an equilibirum. Transposons copy themselves till the reduced lifespan/health isn’t worth it to double the chance of being inherited.
Even if people with less active transposons have slightly more children that’s only one part of the evolutionary equation.
The frame I was taught is evolution= natural selection + mutation + gene drift. Mutations are a force for increased transposon count (and if there’s more DNA repair there are less mutations). Natural selection is a force for decreased transposon count. You would expect those two forces to find an equilibrium so that the amount of transposons isn’t a problem at the age where an animal bears children. If you have very effecitve germline transposon suppression transposon also evolve to escape the transposon suppression.
When it comes to DNA repair I would expect that it’s simply a cost for a cell to put resources into DNA repair.
Without evolutionary pressure that prevents individuals with more active transposon to reproduce less that just gets the transposons to express themselves more and you have +/- zero.
Sure, but wouldn’t a hunter that stayed physically 25 until the age of 45 have a higher inclusive genetic fitness, all else being equal? (edit circa 2022-07-02: Wow, I was dumb. Red Queen hypothesis, baby.)
All else isn’t equal. Transposons replicate. That’s what transposons are about.
The genetic fitness of the hunter doesn’t really matter (that’s basically the insight Dawkins wrote about in the selfish gene). You have to look at the fitness of the transposon and what’s good for the transposon.
If a transposon copies itself into another chromosome it can increase the chance of being inherited to a child from 50% to 100%. That’s highly useful to the fitness of the transposon and worth slightly reduced lifespan of the child.
Both of those forces are at an equilibirum. Transposons copy themselves till the reduced lifespan/health isn’t worth it to double the chance of being inherited.