Short answer: we’re adaptation executors, not fitness maximizers.
I fully get the point, but this doesn’t by itself explain why superior adaptations haven’t come along. Basically, we need to consider a “constraint on perfection” argument here, and ask what may be the constraints concerned in this case. It is generally possible to test the proposals.
Some obvious (standard) proposals are:
1) Mutations can’t arise to turn TFT into TFT-1
This is a bit unlikely for the reasons I already discussed. We do seem to have slightly different behaviour in the one-shot (or last-round) cases, so it is not implausible that some “mutant” would knock out co-operation completely on the last round (or on all rounds after a certain age—see my Grumpy-Old-Man idea above). There is a special concern when we allow for “cultural” mutations (or learned responses which can be imitated) as well as “biological” mutations.
2) Additional costs
The argument here is that TFT-1 has an additional cost penalty, because of the complexity overhead of successfully detecting the last round (or the only round), and the large negative cost of getting it wrong. Again it faces the objection that we do appear to behave slightly differently in last (or only) rounds, whereas if it were truly too difficult to discrimate, we’d have the same behaviour as on regular rounds.
3) Time-lags
This is the argument that we are adapted for an environment which has recently shifted, so cases of single-round (or known last-round) Prisoner’s Dilemma are much more common than before and evolution hasn’t caught up.
This might be testable by directly comparing behaviours of people living in conditions closer to Paleolithic versus industrialized conditions. Are there any differences in reactions when they are presented with one-shot prisoner’s dilemmas? If one-shot PD is a new phenomenon, then we might expect “Paleo-people” to instinctively co-operate, whereas westerners think a bit then defect (indicating that a learned response is overriding an instinctive response). This strikes me as somewhat unlikely (I think it’s more likely that the instinct is to defect, because there is a pattern-match to “not a member of my tribe”, whereas industrialized westerners have been conditioned to co-operate, at least some of the time). But it’s testable.
A variant of this is Randaly’s suggestion that true last-rounds are indeed new, because of the effect of retaliation against family (which has only recently been prohibited). This has a nice feature, that in cases where the last round truly was the last (because there was no family left), the mutant wouldn’t spread.
4) Side effects
Perhaps the mutations that would turn TFT into TFT-1 have other undesirable side effects? This is the counter-argument to Grumpy-Old-Man mutants invading because they have other positive side effects. Difficult to test this one until we know what range of mutations are possible (and whether we are considering biological or cultural ones).
I fully get the point, but this doesn’t by itself explain why superior adaptations haven’t come along. Basically, we need to consider a “constraint on perfection” argument here, and ask what may be the constraints concerned in this case. It is generally possible to test the proposals.
Some obvious (standard) proposals are:
1) Mutations can’t arise to turn TFT into TFT-1
This is a bit unlikely for the reasons I already discussed. We do seem to have slightly different behaviour in the one-shot (or last-round) cases, so it is not implausible that some “mutant” would knock out co-operation completely on the last round (or on all rounds after a certain age—see my Grumpy-Old-Man idea above). There is a special concern when we allow for “cultural” mutations (or learned responses which can be imitated) as well as “biological” mutations.
2) Additional costs
The argument here is that TFT-1 has an additional cost penalty, because of the complexity overhead of successfully detecting the last round (or the only round), and the large negative cost of getting it wrong. Again it faces the objection that we do appear to behave slightly differently in last (or only) rounds, whereas if it were truly too difficult to discrimate, we’d have the same behaviour as on regular rounds.
3) Time-lags
This is the argument that we are adapted for an environment which has recently shifted, so cases of single-round (or known last-round) Prisoner’s Dilemma are much more common than before and evolution hasn’t caught up.
This might be testable by directly comparing behaviours of people living in conditions closer to Paleolithic versus industrialized conditions. Are there any differences in reactions when they are presented with one-shot prisoner’s dilemmas? If one-shot PD is a new phenomenon, then we might expect “Paleo-people” to instinctively co-operate, whereas westerners think a bit then defect (indicating that a learned response is overriding an instinctive response). This strikes me as somewhat unlikely (I think it’s more likely that the instinct is to defect, because there is a pattern-match to “not a member of my tribe”, whereas industrialized westerners have been conditioned to co-operate, at least some of the time). But it’s testable.
A variant of this is Randaly’s suggestion that true last-rounds are indeed new, because of the effect of retaliation against family (which has only recently been prohibited). This has a nice feature, that in cases where the last round truly was the last (because there was no family left), the mutant wouldn’t spread.
4) Side effects
Perhaps the mutations that would turn TFT into TFT-1 have other undesirable side effects? This is the counter-argument to Grumpy-Old-Man mutants invading because they have other positive side effects. Difficult to test this one until we know what range of mutations are possible (and whether we are considering biological or cultural ones).