Success, therefore, comes from producing as many offspring as possible who go on to produce offspring of their own. Merely producing many offspring is no guarantee that some of them will survive; human babies require parental investment in the form of food, shelter, protection from predators, education, etc. to ensure that they survive to sexual maturity and are able pass on their parent’s genes to future generations. So there is a trade off between energy spent reproducing and energy spent investing; energy spent investing cannot be used for reproduction and energy spent reproducing cannot be invested.
Evolutionary explanations of parental investment concern the conflicts that arise over the amount of parental investment provided. These conflicts can occur between parents (which sex invests more) and between parents and offspring (how much investment each offspring gets compared with its siblings).
