[belorn]

I can highly recommend Behavioral evolution and in particular robert sapolsky writings, but to give a summery, a common categorization in behavioral evolution is pair-bonding species vs tournament species.

In tournament species it is the observed strategy of males to devote as little as possible on offspring and to maximize impregnate as many females as possible, while the female strategy is to maximize the gene quality as that is the only contribution to the success that the male gives to the offspring (and the continuation of her genes if one view natural selection to be about the continuation of genes). Males tend to be large then females, and usually evolve disadvantaging traits for survival in favor of traits that increase competitiveness against other males. A typical example would be Elephant seals. Common traits among tournament species is a large difference life expectancy among male and females, and only a short portion of the male population that successfully reproduce.

Pair-bonding species create a balance where both the male and female spend approximation the same amount of energy (resources) on offspring. A big benefit is the extra insurance that two parents provide, and there is a directly associated chance for twins in pair-bonding species. A typical example is most birds who spend approximating similar amount building nest, brooding, collecting food and feeding the offspring. Many people think when they see a bird sitting on eggs that it must be the female, or when one is carrying nest material that it must be the male, but that is just us projecting our culture onto nature.

And to answer the question on where humans fit in this categorization, the answer is somewhere in the middle and it is unclear why we have not settled on a single strategy.

[n4r9]

Thanks. If I remember rightly this is also touched on in the Selfish Gene, though it's been over a decade since I read that.