I once was hiking in the Tatras and upon reaching a part that was more difficult, heaved a sigh and said “Pizdec”. Everybody laughed, even people from further away.
That’s only if you assume male-to-female ratio of 1:1 if they had, say, 10 women for each man, they would only lose 10% of their population per generation. However, if roughly one in ten pregnancies were with twins, the population would be stable.