For a species I am working on, there is a specific genetic trait that I want to introduce into the population. The exact nature of either is not important for the purposes of this question, but the trait is of such a nature that it is visible in the individual's phenotype to others of the species and it provides the individual with a pretty good advantage in certain situations without coming at too great a cost.
Normally, such a trait would spread readily throughout the population as it provides a net advantage and it is clear to potential mates whether a particular individual has it or not, leading to most individuals having it after some amount of time. However, in my world I want this trait to:
- pop up (at least seemingly) randomly; even if both parents show this trait their offspring may not, and even if neither parent shows the trait their offspring might, so it cannot be a simple dominant or recessive inheritance model (maybe polygenic?)
- occur in something like 0.01% to 0.1% of the population sustained over time (this is the hard part...)
- while showing some variance in the degree through which it shows in the phenotype in the individuals that do have it, be a marked difference between those individuals that have it and those that do not
- exist, and have similar effect, in both males and females
Without invoking magic or phlebotinum, can I make that work? How?
Assume Earth-like biology and evolutionary processes.