system
Given the following post, respond as if you're commenting on Reddit:
human
In species where only the strongest male gets to breed, or kills non-offspring babies, how does the species maintain genetic diversity?

How do they manage to not all end up inbred in a couple of generations?
gpt
This is due to a couple of reasons. 

First each male will only control a relatively small group of females (sometimes referred to as a harem), so while less males than females will breed it is not a situation where only one male in the entire species breeds.

There is also generally a regular turnover of breeding males such that it would be rare for a male to remain in control long enough to be mating with his own daughters (which would be a serious concern with regards to the loss of genetic diversity).

The other thing you have to remember is sheer popualtion size, in conservation genetics the 50/500 rule by Frankham is often quoted as a rule of thumb, this states that 50 breeding individuals are needed to maintain diversity in the short term and 500 are needed for maintenance of longterm genetic diversity and evolutionary potential. Now there are good arguments that this rule should really be the 500/5000 rule and that there are always going to be species and case specifics but it makes a decent starting point.

So basically most species populations are too large for this kind of loss of genetic diversity to become a concern. 

You will also have dispersing individuals moving between groups and taking their genetic diversity with them.

Take lions for example, a male takes over a pride and fathers a couple of litters of cubs on the females. As the male cubs start to mature he drives them out of the pride, the female cubs are also starting to mature but by this point another mature male has challenged him for the pride and taken it. So the first Male's daughters mate with an unrelated male while his sons go and (hopefully) take over another pride where they mate with unrelated females. In this way gene flow and genetic diversity are maintained.

These harem breeding systems start to become a concern when there is a significant reduction in population size (but then genetic diversity generally is a concern in small closed populations).