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Caledonian2 comments on The Tragedy of Group Selectionism - Less Wrong

36 Post author: Eliezer_Yudkowsky 07 November 2007 07:47AM

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Comment author: Caledonian2 08 November 2007 12:15:24PM 2 points [-]

To get group selection out of this scenario, you would have to have one fox group with a lower-than-optimal breeding rate, which let the rabbit population expand, which lessened the chance of a crash in food supply that would wipe out the population. Then that fox group would survive, and the neighboring groups would perish. But there is no way to enforce this pact of lower-than-optimal breeding rates in the first place.

Enforce? You don't need to enforce something that's build into organism's biology - and in the scenario you describe, their reduced rate would be the 'optimal' solution.

Even if a trait offers serious advantages in between-group competition, if it's a disadvantage in within-group competition, it will often dwindle and die out over time. What matters is whether the trait can make more copies of itself than will be eliminated; if it can't, there's no mechanism for it to persist, but if it can, one way or another, its frequency will increase. There has to be replication on the level of the group, not just on the level of the individual, for group-level benefits to cause traits to persist.

In an environment where new groups are frequently formed from randomly-selected subsets of previous groups, and groups compete with each other, the founder effect can amplify the frequency of traits that benefit the group but are disadvantageous for the individuals carrying them. Now groups are acting as a unit of replication, and so selection forces can maintain traits on this level.

This is why mice don't go extinct even though they're parasitized by the replicator gene. Sure, the gene rapidly dominates any group it's introduced to, and prevents successful reproduction within that group, but there are enough obstacles to divide the total mouse population into smaller groups in the short term. Inside any one group, not having the gene loses out to having it every time. But the constant establishment of new groups, and the temporary limits to gene spread between groups, together make it possible for the gene-absense to persist. If you removed the restrictions on gene flow the parasite gene would spread throughout the entire mouse population and they'd all die out. If there aren't enough distinct groups, group-level selection doesn't 'work' - just as individual-level selection doesn't 'work' when there aren't enough individuals.