It’s worth starting by noting, that male and female births are not 50-50. While conceptions are 50-50, births aren’t and there are mechanisms that terminate pregnancies unsuccessfully that have different likelihoods based on gender.
While it makes sense that the value is near 50% for humans it’s not exactly both in reality and in computer models I did for human evolution (and it surprised me).
Sexual selection is very useful. In humans, mitochondrial DNA is only passed maternally and we see that evolution reduced the number of mitochondrial genes to a minimum.
For each of the chromosomes we get one from our mother and one from our father. There’s no easy way to give 1.25 from the mother and 0.75 from the father. If we get two of one of the chromosomes or none from one parent in most cases the pregnancy terminates unsuccessfully and in the few remaining cases, it produces severe harm (like down syndrome).
What asymmetries did you introduce into your simulations that lead to a difference? Models with no gender differences but with mandatory sexual reproduction usually tend to be 50⁄50 in my experience.
My models had humans with their full 46 chromosomes and multiple genes per chromosome. In addition, I have transposons on those chromosomes. I also tried to have a model of mating behavior where males and females obviously have different roles.
Mutations on the x-chromosome lead more frequently to pregnancy termination in male offspring. This is pretty obvious given that female offspring have more redundancy when it comes to the X chromosome.
The transposon-related pregnancy terminations that in turn terminate more female pregnancies than male ones are less obvious. I think I have some insight there that could be publishable. If anyone wants to collaborate on a paper I’m happy to say more privately.
Transposons and their effects get often not taken as seriously as they should.
I think this makes sense because eggs are haploid (already only have 23 chromosomes) but a natural next question is: why are eggs haploid if there is a major incentive to pass more of the 46 chromosomes?
It’s worth starting by noting, that male and female births are not 50-50. While conceptions are 50-50, births aren’t and there are mechanisms that terminate pregnancies unsuccessfully that have different likelihoods based on gender.
While it makes sense that the value is near 50% for humans it’s not exactly both in reality and in computer models I did for human evolution (and it surprised me).
Sexual selection is very useful. In humans, mitochondrial DNA is only passed maternally and we see that evolution reduced the number of mitochondrial genes to a minimum.
For each of the chromosomes we get one from our mother and one from our father. There’s no easy way to give 1.25 from the mother and 0.75 from the father. If we get two of one of the chromosomes or none from one parent in most cases the pregnancy terminates unsuccessfully and in the few remaining cases, it produces severe harm (like down syndrome).
What asymmetries did you introduce into your simulations that lead to a difference? Models with no gender differences but with mandatory sexual reproduction usually tend to be 50⁄50 in my experience.
My models had humans with their full 46 chromosomes and multiple genes per chromosome. In addition, I have transposons on those chromosomes. I also tried to have a model of mating behavior where males and females obviously have different roles.
Mutations on the x-chromosome lead more frequently to pregnancy termination in male offspring. This is pretty obvious given that female offspring have more redundancy when it comes to the X chromosome.
The transposon-related pregnancy terminations that in turn terminate more female pregnancies than male ones are less obvious. I think I have some insight there that could be publishable. If anyone wants to collaborate on a paper I’m happy to say more privately.
Transposons and their effects get often not taken as seriously as they should.
I think this makes sense because eggs are haploid (already only have 23 chromosomes) but a natural next question is: why are eggs haploid if there is a major incentive to pass more of the 46 chromosomes?
If you would say that there are two copies of chromosome 11 in the egg and none in sperm, you would lose sexual selection for chromosome 11.