I'm working on creating a species that favours small families for a number of reasons, and have no interest in 'breeding as much as possible'. As a consequence, their population size is small. But how small can a population be, without running (ever) into problems with genetic diversity? I'm interested in more than 'survivability'; the species' gene pool should not degenerate (some margin allowed). I'm looking for some well-founded answers or directions.
Assume that genetics for this species works similar to that of humans, and that their gene pool is of good quality at the start. You can also assume that they choose partners wisely, but there is no designation of partners, so margin is necessary. They have good health care and low child mortality rates. Assume that at least 90% of the population reaches at least fertile age.
- Average number of children born is two (might be increased to three if that is necessary to sustain the population)
- Species is monogamous
- No genetic manipulation
This question differs from the question What is the minimum human population necessary for a sustainable colony? because:
- It is assumed (for a population of 80 / 160) that the population will mingle with a larger population after ten generations
- The population of 350 still resulted in some genetic issues (of which some disastrous)
This question differs from the question How many humans do you need to maintain a population indefinitely? because of the given context that everyone in the group is the genetic parent of exactly two children each with a different partner which is violating above assumptions.
This question differs from the question Minimum Population For a High Tech Society? because it is not about genetic diversity, but the skills and intelligence needed to run a high tech society (which is possibly a follow-up question).
Some other questions touch this topic, but they are (slightly) different in either the assumptions or the direction of the question.