The evolution of parental optimism.

In choosing how many offspring to rear per cycle, parents commonly starts with more than they really can afford, then allow/encourage some to die. Multiple incentives for overproduction exist. By creating marginal young, parents may: (1) capitalize when unpredictable resources prove unusually rich; (2) supply these as food or servants for core brood members; and/or (3) have a stock of replacements for any core offspring that either fail to survive or develop poorly.