At least this is what the observations on the fertility of insects and other animals and viability of their posterity tell us. Scientists have noticed that the denser is the population of insects on a given area, the more times they mate with each other, which leads to the lower amount of eggs laid per individual, but the higher is the viability and adaptability of these eggs, larvae and imago hatched and developed from them. Sometimes this interesting phenomenon can be observed not only in the first, but also in the second generation. And vice versa, the scarcer is the insects’ population, the less copulation they have. It results in weaker posterity, but the larger amount of it.
So, there seems to be a certain natural mechanism of regulating populations. Scarce population with fewer opportunities of mating tends to have relatively weak posterity. In order to survive organisms there need to lay more eggs / give birth to more children. Dense population, on the contrary, offers more opportunities for copulating, which increases the viability of future generations. So, its members do not need to have high fertility to survive. And in fact it should be reduced to prevent overgrowth of the population beyond certain limits.
But, of course, the Nature always has a number of exceptions to make life more diverse and interesting. For example, the fly Rhagoletis likes to have it all at once: to be in large numbers, to have “sex” many times, to lay highly viable eggs and in very large quantities. Basically, it lives by the principle “If to do anything, then do it a lot”.
And we, humans, are subject to the same regulatory mechanism with some exceptions in our communities, aren’t we?
Note: The post is based on the book by Marikovskii, P. I. “Insects Defending”.