Tuesday, December 1, 2009

Parent-Offspring Conflict

This morning I read Robert Triver's article "Parent-Offspring Conflict" that appeared in the journal American Zoologist way back in 1974. It is a very important article on the subject of evolution, and identified the process from which the article takes its title.

The article is divided into several main subsections:
  1. Parent-offspring conflict over the continuation of parental investment
  2. Conflict throughout the period of parental investment over the amount of parental investment
  3. The time course of parent-offspring conflict
  4. Disagreement over the sex of the offspring
  5. The offspring as psychological manipulator
  6. Parent-offspring conflict over the behavioral tendencies of the offspring
  7. Conflict over the adult reproductive role of the offspring
  8. The role of parental experience in parent-offspring conflict
According to evolutionary theory, each organism attempts to maximize its reproductive success and perpetuate copies of its own genes. Since the genes of the parents and offspring are different, though at the same time related, this creates and undercurrent of competition in an otherwise nurturing relationship. Conflict between parent and offspring occurs in any sexually reproducing organisms, and the parental investment in the offspring either positively or negatively affects the fitness of both in different ways. Offspring are not "passive vessels into which parents pour the appropriate care. Once one imagines offspring as actors in this interaction, then conflict must be assumed to lie at the heart of sexual reproduction itself."
I found several sections in the paper particularly interesting. This one underscores the situation of children in relation to their parents:
Throughout the period of parental investment the offspring competes at a disadvantage. The offspring is smaller and less experienced than its parent, and its parent controls the resources at issue. Given this competitive disadvantage the offspring is expected to employ psychological rather than physical tactics.
And this describes why parents want their children to be nice to each other, though the children are more likely to fight among themselves:
An individual is only expected to perform an altruistic act toward its full-sibling whenever the benefit to the sibling is greater than twice the cost to the altruist [because they are only half related to their siblings]... But parents, who are equally related to all of their offspring, are expected to encourage all altruistic acts among their offspring in which the benefit is greater than the cost, and to discourage all selfish acts in which the cost is greater than the benefit.

Source:  Trivers, Robert L.  "Parent-Offspring Conflict" American Zoologist 1974 14(1):249-264

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