2
$\begingroup$

in this world, it's a number of small communities with a postindustrial level of technology where the male minority rules over the female majority with only one male born per a 100 females, with males making up only 1% of the total population. With this ratio, how would this species avoid genetic stagnation? like for example, with the genes these males not causing hereditary illnesses and disabilities down the road due to lack of genetic diversity?

And how would they avoid such problems without outside intervention?

$\endgroup$
5
$\begingroup$

Low estimate: 2,525. High estimate: 25,250

A scenario like this is fine as long as the population is above a certain manageable size. Let's say that given a 1:1 male-female population, the community is required to be above the population n in order to avoid inbreeding. In this hypothetical population of 1:100 male-female, the way breeding pairs work is that every member of the population has 99 sets of half-siblings (though mostly sisters). The females just need to find a male which isn't related to them, which is simple enough to find, as any their family structure will still work the same way backwards, so all they have to do is check the prospective male's parents, grandparents, and possibly great-grandparents, and if that checks out, than it's fine. That means that this population will still need the same number of males that a 1:1 population has, but will require 100x the females. We take the '50/500' rule, which says that a population of 50 is necessary to prevent inbreeding, and 500 is needed to reduce genetic drift and apply our requisite formula - in humans it's 25 males, 25 females, so in this species its 25 males, 2,500 females; or 250 males, 25,000 females, depending on how secure you want to be. The 50/500 rule, by the way, is a very loose rule of thumb - the number itself greatly differs from species to species based on a lot of different factors but 50/500 is a good starting ballpark estimate.

Naturally avoiding inbreeding would be difficult, but for the most part it doesn't matter as long as direct incest is avoided and indirect incest (i.e. cousins) doesn't repeatedly happen, which is usually possible. (As in it doesn't matter solely from a health perspective.) If you wanted to be gimmicky about it, you could have everyone wear family crests, or something of that nature so that the other members would know whether or not they're from the same family.

$\endgroup$
2
$\begingroup$

The big step to prevent the bottle neck of male genetics is stern incest taboos. You must marry someone more distantly related than a first cousin. Which, given the number of half-siblings your parents had, will be hard. Travel and relations with other communities will be vital.

On the other hand, it's not a stable situation. If they have a postindustrial level, they could probably do something to increase the number of boys, and furthermore, they would. And if they could not do it, the number would increase anyway, albeit more slowly. Fisher's principle ensures it. Let us assume that every woman in this world has two children. Biology ensures therefore that every man (on average) has two hundred children.

If they are daughters, a woman has four grandchildren. If one is a boy, she has two hundred and two grandchildren. If both are boys, she has four hundred grandchildren.

Likewise, a man who had two hundred daughters would have four hundred grandchildren. A man who had even ten sons would have two thousand, three hundred and eighty grandchildren.

The slightest tendency to have more sons would be so rewarded evolutionarily that the shift would be inevitable.

$\endgroup$
1
  • $\begingroup$ Clearest explanation of that principle I ever remember seeing. When I've tried to explain it myself, I've become so baffled that I started to doubt whether I understood it myself. $\endgroup$
    – A. B.
    Jul 8 '20 at 2:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.