Life history is a collection of hypotheses that explain why animals differ in so called life history traits which include size at birth, growth and developmental schedules, age and size at maturity, number, size, and sex ratio of offspring, reproductive schedules, sex drive, mortality schedules and extent of investment in the offspring and cultural sophistication. These traits are explained as a result of the specific properties of the ecologies the species evolved in.
r/K-selection[edit | edit source]
r/K selection was the predecessor of the life history theory which superseded it, adding additional mechanisms explained in the sections below (tbd). At the core of r/K selection is a distinction between two kinds of ecologies which are opposed on the spectrum of ecological harshness:
- Unpredictable, but easy ecologies, e.g. tropical regions are full of competing animals, but food is readily available. Animals in such ecologies are said to be r-selected, where r is the growth rate and r-selected means maximizing growth rate. This means making as many offspring as possible and not investing much in them, hoping they will make their way through the unpredictable but easy environment, i.e. requiring little guidance on part of the parents. R-strategists have a fast life history (speed).
- Predictable, but harsh ecologies, e.g. cold regions have relatively low population counts as food is hard to attain through the winter. Animals in such ecologies are said to be K-selected, where K is the carrying capacity of the environment. In harsh ecologies this capacity is low, so species produce few offspring and care for them, and maintain the population size near the maximal carrying capacity. K-selected species evolve "K-strategies" that emphasize high levels of parental care, resource acquisition, kin provisioning, and social complexity. The K-strategy requires more complex nervous systems and larger brains. K-strategists have a slow life history.
Sex differences[edit | edit source]
Even though women's sexual strategy is often purported to be slower, this really only seems to apply to their more coy, passive and choosy sex drive and much more limited reproductive rate. In truth, women lose interest in long-term romantic investment a lot sooner than men and yield nearly the same rate of affairs. In fact, biochemical research points to a natural four-year sexual cycle for the human female. A woman’s natural tendency is to “liberate” herself from her mate after that point. This is in line with divorce statistics where women are the initiator 75% of the time. Moreover, women mature sooner than men, with early maturation being a key aspect of fast LH predisposition. This, however, may simply be a result of men selecting for neoteny for paternity assurance or due to women getting easier access by looking cute.
So, even though women's life history speed is slower in terms of reproductive rate and choosiness, their long-term strategy seems to be actually less r-selected than men's, implying less long-term investment in the offspring and hence less compatible with modern, highly ordered and structured civilization.
This sex difference may also stem from the fact that women have overall been less subject to selective pressures as they reproduced twice as often as men. For this reason, women's sexuality may be stuck in a more r-selected past. Women's tendency to switch mates has also been explained by the mate switching hypothesis as a means to ensure a suitable provider and protector all the time, which women are thought to depend on by bodyguard hypothesis. Another explanation could be that modern requirements are simply a an evolutionary mismatch that only emerges when women are economically independent and liberated such that their hypergamy, choosiness and fickleness becomes more exposed.
Women's lower capacity of forming long-term friendships, as evidenced by their higher rate of gossipy and destructive intrasexual competition, is also indicative of a faster life history speed, as such behavior is not aimed at furthering long-term investment and social cohesion.
References[edit | edit source]
- https://toqonline.com/archives/v7n2/v7no2_Devlin.pdf (Langley 2005)