I have thought that the Ocampa have multiple births, that's the only way they wouldn't die out in a few generations with only one pregnancy per female. Her single birth with Lynnis (and her son in String Theory novels) could be due to them being hybrids, or just that single births are rare but still happen.
Good point. I never thought of that. If single births were the norm. The Ocampa population would be halved (at best) every generation (what, say 4 years?) and go extinct pretty fast. Let's do some fun math.
That can be represented as an exponential growth problem: A=Pe^(rt), where A=accumulate population (let's say, to reach a final population of 1% of the original), P=the beginning population (let's just say 100 to represent 100%), e=exponential e (about 2.718), r=rate of decline (-.5 in this case), and t=time (measured in generations).
If we do the math, t=9.2 generations. Assuming an average 4-year generation, the Ocampa population would dwindle down to almost nothing in less than 40 years.
Good theory. The Caretaker must have been imposing external forces to manage the population, maybe even more so towards the end as he got weaker.