Hidden Games

There is no single human nature.   This is obvious enough – people vary strongly in their psychology and behavior. The differences show up early in life and don’t seem to be affected much by parental rearing style.   It would be nice to understand more about the ultimate causes of variation in human personality,  partly because of practical implications, mostly because we find ourselves very interesting.

To some extent, the ultimate source must be forces other than natural selection:  mutational pressure, infectious disease, and new environmental insults.  Mutations happen, viruses get into the brain, you may even have a steel rod fired through your skull, like Phineas Gage.  Such things can affect your personality.  In general, one would expect that these are the causes behind obviously maladaptive behavioral syndromes, like homosexuality and schizophrenia.

 Most human behavior is universal and adaptive, or used to be in past environments .  We eat when we’re hungry, fear spiders and snakes, love our children – these essentially universal behaviors are the products of natural selection.   Behavioral patterns of this sort exist because they have worked over the long haul, worked in the sense that their bearers left descendants.   Such patterns can be thought of as strategies  –  patterns or rules of conduct that, on average, led to reproductive success in the human past.

But to what extent is variation in human behavior adaptive? Why shouldn’t there be a single best strategy?  Often there  is, but not always.  It depends on whether the payoff of a particular course of action is frequency-dependent – in other words, depends on what other individuals do.  Running from a  forest fire pays off whether anyone else runs or not, but the payoff of running for tribal chief decreases as the number of candidates increases. If everyone is passive (a ‘dove’), aggressive individuals (‘hawks’) prospers, but as hawks becomes more common, they increasingly run into and fight other hawks, so their payoff decreases.  If the cost of fighting among hawks are high enough,  the equilibrium solution is a mixed state consisting of both hawks and doves.  Thus there is no single best solution, no single optimal behavior – this is often the case with social interactions.

The next question is whether adaptive variation in behavior/personality  is fixed or flexible, heritable or not.   In other species,  we see both. Sometimes an individual can pick one or another life strategy based on exterior clues.  If a female bee larvae is fed royal jelly, she becomes a  queen, otherwise she becomes a sterile worker.  The capability to assume those different roles is adaptive and presumably a result of natural selection, but it is not noticeably heritable, because all females bees have it.  In other cases, like those pesky fire ants that  exhibit single-queen and  Los Angeles-style multi-queen colonies, the two morphs are determined by the two alleles of a single gene, and the behavior difference is heritable as all get out –  and also shaped by natural selection.

 Since we are arguably a lot smarter than ants or bees, you might think that most adaptive personality variation in humans would be learned (a response to exterior cues) rather than heritable.  Maybe some is, but much variation looks heritable. People don’t seem to learn to be aggressive or meek – they just are, and in those tendencies resemble their biological parents.   I wish I (or anyone else) understood better why this is so, but there are some notions floating around that may explain it.  One is that jacks of all trades are masters of none: if you play the same role all the time, you’ll be better at it than someone  who keep switching personalities.  It could be the case that such switching is physiologically difficult and/or expensive.  And in at least some cases, being predictable has social value.  Someone who is known to be implacably aggressive will win at ‘chicken’. Being known as the sort of guy who would rush  into a burning building to save ugly  strangers may  pay off, even though actually running into that blaze does not.
Also, if a particular role or personality type only became viable recently – say,  20,000 years ago –  a mutation that induces that personality will spread.  Initially it will not be part of some super-flexible system; the required modifier genes, that would  turn those tendencies on when they pay and off when they don’t,  would take  a long time to evolve.

hn Tooby and Leda Cosmides, leading evolutionary psychology mavens, have argued strongly against the possibility of heritable, adaptive behavioral  variation in humans.  In fact  their arguments imply  that no such thing should exist in any  species, and  since we’ve found genetic morphs in lizards, birds, crustaceans, ants,  and butterflies, it’s safe to say that John and Leda  are wrong on this. But at least one of their arguments is interesting: they argue that adaptations, including behavioral adaptations,  are usually generated by complex,  co-adapted sets of genes (true), and that such gene complexes would be broken up by sexual reproduction (also true):  even if Dad had a set of alleles that made him a natural blacksmith or tap dancer,  his kids would never  inherit that whole set and the talent should disappear.  I think they’re on to something with this argument, because it seems that in a significant numbers of cases, these genetic morphs are determined by a single gene: different alleles of that gene specify different morphs. Maybe the heritable variant is in some way a simple trait: I can imagine a number of ways in which that could work. For example, what if simply losing a particular complex adaptation is adaptive when rare?  I can easily believe that a complex behavioral adaptation could be stopped cold by a  single mutation.  Or, for that matter, what if greatly intensifying a particular behavior or drive – turning up the volume knob –  was adaptive when rare? Can I imagine a simple mutation that turns up the volume in some way? Surely.  And, of course, such simple initial changes can be gradually refined by natural selection.

People underestimate the information that can be packed into a  single protein. A protein 200 amino acids long could express (21)**200 difference sequences: that’s a lot of possible messages.  21 instead of 20, because of seleno-cysteine.  I’m not even counting the impact of sequence variation in the promoter region.

There is another way in which a whole different life-strategy can be packed into a single variant allele: the gene can act as a switch. The sex-determining gene SRY is the best example of this.  There are many genes  that are fully expressed only in one sex while existing (of course) in both. Modifier genes sense the state of the switch and turn other genes on and off accordingly.  Every guy has the necessary genes for a uterus, but they just sit there, waiting for a chance to show their stuff in a female descendant.  The same thing could happen with morphs: probably does happen.  It would be interesting to check for genes that are highly expressed in the single-queen fire ant morph but not in the multi-queen morph.  There has been plenty of time for this to happen,  since the polymorphism is millions of years old and predates the species.
This kind of game-theoretic genetic variation, driving  distinct behavioral strategies, can have some really odd properties.  For one thing, there can be more than one possible stable mix of behavioral types even in identical ecological situations.  It’s a bit like dropping a marble onto a hilly landscape with many unconnected valleys – it will roll to the bottom of some valley, but initial conditions determine which valley. Small perturbations will not knock the marble out of the valley it lands in.   In the same way, two human populations could fall into different states, different stable mixes of behavioral traits, for no reason at all other than chance  and then stay there indefinitely.  Populations are even more likely to fall into qualitatively different stable states when the ecological situations are significantly different.
In some cases, the states are not even time-stable.  There could be periodic oscillations.  Consider those crazy cichlids. There is a kind of cichlid in Lake Tanganyika that lives by eating the scales of larger fish.  It attacks by swimming up from behind and snatching a scale or two from the side of its prey. Its mouth is twisted to the side, which aids in this specialized form of attack.  Some individuals have mouths twisted to the right ( right-handed fish) and others are left-handed.  Right-handers attack their prey from the left and left-handers from the right. Prey do their best to avoid these attacks, but they cannot be vigilant simultaneously against attacks from the left and from the right.  The handedness of the scale-eating cichlids is heritable and can evolve, as ids the tendency of other fish to be  protect their left or their right sides.   When most fish are defending against right-handed scale-eaters, southpaws have an advantage, and vice versa.  It appears that these two forms cycle over time, never reaching an equilibrium.

Barry Sinervo’s lizards have three male morphs: aggressive orange males that dominate blue males but that cannot compete with yellow males that imitate females – yellow males that  are successfully kept out by territorial blue males.  Scissors, paper, rock – but there is more since the same alleles in females results in r-females that lay many small eggs and k-females that lay a few large eggs.   Not too far away, the same species has only one male morph, the blues: either by chance or because of a different ecological situation,  the species has fallen into an entirely different societal pattern.

 What this means,  think, is that it is entirely possible that human societies fall into  fundamentally different patterns because of  genetic influences on behavior that are best understood via evolutionary game theory.  Sometimes one population might have a psychological type that doesn’t exist at all in  another society,  or the distribution could be substantially different.  Sometimes these different social patterns  will be predictable results of different ecological situations, sometimes the purest kind of chance. Sometimes the  internal dynamics of these genetic systems will produce oscillatory (or chaotic!) changes in gene frequencies over time, which means changes in behavior and personality over time.   In some cases, these internal genetic dynamics may be the  fundamental reason for the rise and fall of empires.    Societies in one stable distribution, in a particular psychological/behavioral/life history ESS, may simply be unable to replicate some of the institutions found in peoples in a different ESS.

Evolutionary forces themselves vary  according to what ESS you’re in.  Which ESS you’re in may be the most fundamental ethnic fact, and explain the most profound ethnic behavioral differences

 Look, everyone  is always looking  for the secret principles that underlie human society and history, some algebra that takes mounds of historical and archaeological  data  – the stuff that happens – and explains it in some compact way, lets us understand it,  just as continental drift  made a comprehensible story out of geology. On second thought, ‘everyone’ mean that smallish fraction of researchers that are slaves of curiosity…

This approach isn’t going to explain everything –  nothing will.  But it might explain a lot, which would make it a hell of a lot more valuable than modern sociology or cultural anthropology.  I would hope that an analysis of this sort might help explain  fundamental long-term flavor difference between different human societies, differences in life-history strategies especially (dads versus cads, etc).  If we get particularly lucky, maybe we’ll have some notions of why the Mayans got bored with  civilization,  why  Chinese kids are passive at birth while European and African kids are feisty.  We’ll see.

Of course we could be wrong.  It’s going to have be tested and checked:  it’s not magic. It is based on  the realization that the sort of morphs and game-theoretic balances we see in some nonhuman species are if anything more likely  to occur in humans, because our societies are so complex, because the effectiveness of a course of action so often depends on the psychologies of other individuals – that and the obvious fact that people are not the same everywhere.