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> For instance there is a condition in mice that lives on the male chromosome. It causes all of it's offspring to be male. So all of them also carry this condit

> For instance there is a condition in mice that lives on the male chromosome. It causes all of it's offspring to be male. So all of them also carry this condition. Thus the condition spreads itself twice as much as the competing genes. And so it quickly fixes itself in the population and then there are no more females. It is not at all guaranteed that this condition would lead to the extinction of a population unless that population was of trivial size (and therefore unstable). Consider that as the fraction of males in a population goes to 1, the reproductive success of males goes to 0 and the reproductive success of females goes to 1. Therefore we should expect that there will be an extremely strong selective pressure on producing female offspring in greater and greater proportion.

3pt14159 10y ago
Only on the first order. Say population is 90% conditioned male (ie, only male children), 5% normal male, and 5% normal female. Only 1 in 19 males mate, while 100% of females mate. Only those females that mated with normal males produce female children. Which means that barring some sort of mutation or drift, the population will eventually go extinct. One possible solution is that a normal male may have a distinctive feature that a percent of females find attractive which could be selected for.
- AstralStorm 10y ago
  Another solution is that the broken males will engage in some sort of discernible behaviour. Yet another is that smaller populations with this issue will survive in places that couldn't be reached by the damaged one and will repopulate.
Houshalter 10y ago
But the males without the gene are indistinguishable from those with it. They reproduce at exactly the same rate - there is no selection pressure for normal males. You can try it in computer simulations if you like. It would be trivial to set up. Each generation the percent of normal males decreases. Eventually they are all gone.

3pt14159 10y ago

Only on the first order. Say population is 90% conditioned male (ie, only male children), 5% normal male, and 5% normal female. Only 1 in 19 males mate, while 100% of females mate. Only those females that mated with normal males produce female children. Which means that barring some sort of mutation or drift, the population will eventually go extinct. One possible solution is that a normal male may have a distinctive feature that a percent of females find attractive which could be selected for.

AstralStorm 10y ago
Another solution is that the broken males will engage in some sort of discernible behaviour. Yet another is that smaller populations with this issue will survive in places that couldn't be reached by the damaged one and will repopulate.

Houshalter 10y ago

But the males without the gene are indistinguishable from those with it. They reproduce at exactly the same rate - there is no selection pressure for normal males. You can try it in computer simulations if you like. It would be trivial to set up. Each generation the percent of normal males decreases. Eventually they are all gone.