Behavioral Ecology Blog

Published in 1974, this paper is arguably Bob Trivers 2nd most influential paper behind the paper describing reciprocal altruism… Because very few people read long blog posts, and the idea is to introduce these ideas to people that might not already be familiar, I’l go ahead and list the main points/finding, and then go into some brief discussion about a few of the.

The setup, AKA why is there conflict:

• Parental investment (PI) is any activity that increases the survival of offspring. By definition, investment in current offspring decreases investment in future offspring.

• Parents are expected to allocate PI in a manner that maximizes total number of surviving offspring.
• The offspring will attempt to extract the amount of PI that maximizes it’s own survival.
• The amount that optimizes parents reproductive success is necessarily less that that which optimizes individual offspring survival.

Triver’s novel contribution:

• The amount of conflict depends critically on the relatedness between current and future offspring. (Trivers is thinking about inclusive fitness here)

Other points:

• Care is expected to be opposed by natural selection when cost of care exceeds 2 times the benefit (C>2B)
• As relatedness decreases between current and future offspring, the intensity and duration of conflict increases. (inclusive fitness benefits decrease)
  • The side point here is that…

  

• The intensity of conflict increases as the period of PI continues
• Conflict may begin before birth

Maybe it’s obvious, but I’d just like to point out that a similar line of argument can be extended to explain sibling conflict (sibling rivalry) and subsequent parental attempts to mitigate it. Briefly, because siblings compete for the same limited resource (PI), conflict is expected. The interesting part, ad directly relevant to this paper (in fact Trivers mentions it) is that parents will encourage altruistic behavior at a level that is greater that what maximizes offspring fitness.

In summary, this is a classic paper as measured by it’s relevance to multiple different fields. While Hamilton gave us inclusive fitness theory- Trivers gave us a way to apply it.
TRIVERS, R.L. (1974). Parent-Offspring Conflict. Integrative and Comparative Biology, 14(1), 249-264. DOI: 10.1093/icb/14.1.249