The Psychological Unity of Humankind

Fol­lowup to: Evolu­tions Are Stupid (But Work Any­way), Evolu­tion­ary Psychology

Biolog­i­cal or­ganisms in gen­eral, and hu­man brains par­tic­u­larly, con­tain com­plex adap­ta­tions; adap­ta­tions which in­volve many genes work­ing in con­cert. Com­plex adap­ta­tions must evolve in­cre­men­tally, gene by gene. If gene B de­pends on gene A to pro­duce its effect, then gene A has to be­come nearly uni­ver­sal in the gene pool be­fore there’s a sub­stan­tial se­lec­tion pres­sure in fa­vor of gene B.

A fur coat isn’t an evolu­tion­ary ad­van­tage un­less the en­vi­ron­ment re­li­ably throws cold weather at you. And other genes are also part of the en­vi­ron­ment; they are the ge­netic en­vi­ron­ment. If gene B de­pends on gene A, then gene B isn’t a sig­nifi­cant ad­van­tage un­less gene A is re­li­ably part of the ge­netic en­vi­ron­ment.

Let’s say that you have a com­plex adap­ta­tion with six in­ter­de­pen­dent parts, and that each of the six genes is in­de­pen­dently at ten per­cent fre­quency in the pop­u­la­tion. The chance of as­sem­bling a whole work­ing adap­ta­tion is liter­ally a mil­lion to one; and the av­er­age fit­ness of the genes is tiny, and they will not in­crease in fre­quency.

In a sex­u­ally re­pro­duc­ing species, com­plex adap­ta­tions are nec­es­sar­ily uni­ver­sal.

One bird may have slightly smoother feathers than an­other, but they will both have wings. A sin­gle mu­ta­tion can be pos­sessed by some lucky mem­bers of a species, and not by oth­ers—but sin­gle mu­ta­tions don’t cor­re­spond to the sort of com­plex, pow­er­ful ma­chin­ery that un­der­lies the po­tency of biol­ogy. By the time an adap­ta­tion gets to be re­ally so­phis­ti­cated with dozens of genes sup­port­ing its highly re­fined ac­tivity, ev­ery mem­ber of the species has some ver­sion of it—bar­ring sin­gle mu­ta­tions that knock out the whole com­plex.

So you can’t have the X-Men. You can’t have “mu­tants” run­ning around with highly de­vel­oped ma­chin­ery that most of the hu­man species doesn’t have. And no, ex­tra-pow­er­ful ra­di­a­tion does not pro­duce ex­tra-po­tent mu­ta­tions, that’s not how it works.

Again by the na­ture of sex­ual re­com­bi­na­tion, you’re very un­likely to see two com­plexly differ­ent adap­ta­tions com­pet­ing in the gene pool. Two in­di­vi­d­ual alle­les may com­pete. But if you some­how had two differ­ent com­plex adap­ta­tions built out of many non-uni­ver­sal alle­les, they would usu­ally as­sem­ble in scram­bled form.

So you can’t have New Hu­mans and Old Hu­mans ei­ther, con­trary to cer­tain sci­ence fic­tion books that I always found rather dis­turb­ing.

This is like­wise the core truth of biol­ogy that jus­tifies my claim that Ein­stein must have had very nearly the same brain de­sign as a village idiot (pre­sum­ing the village idiot does not have any ac­tual knock­outs). There is sim­ply no room in re­al­ity for Ein­stein to be a Homo no­vis.

Maybe Ein­stein got re­ally lucky and had a dozen not-too-un­com­mon kinds of smoother feathers on his wings, and they hap­pened to work well to­gether. And then only half the parts, on av­er­age, got passed on to each of his kids. So it goes.

“Nat­u­ral se­lec­tion, while feed­ing on vari­a­tion, uses it up,” the say­ing goes. Nat­u­ral se­lec­tion takes place when you’ve got differ­ent alle­les in the gene pool com­pet­ing, but in a few hun­dred gen­er­a­tions one allele wins, and you don’t have com­pe­ti­tion at that allele any more, un­less a new mu­ta­tion hap­pens to come along.

And if new genes come along that de­pend on the now-uni­ver­sal gene, that will tend to lock it in place. If A rises to uni­ver­sal­ity, and then B, C, and D come along that de­pend on A, any A’ mu­ta­tion that would be an im­prove­ment on A in iso­la­tion, may break B, C, or D and lose the benefit of those genes. Genes on which other genes de­pend, tend to get frozen in place. Some hu­man de­vel­op­men­tal genes, that con­trol the ac­tion of many other genes dur­ing em­bry­onic de­vel­op­ment, have iden­ti­fi­able analogues in fruit flies.

You might think of nat­u­ral se­lec­tion at any given time, as a thin froth of vari­a­tion fran­ti­cally churn­ing above a deep, still pool of uni­ver­sal­ity.

And all this which I have said, is also true of the com­plex adap­ta­tions mak­ing up the hu­man brain.

This gives rise to a rule in evolu­tion­ary psy­chol­ogy called “the psy­cholog­i­cal unity of hu­mankind”.

Don­ald E. Brown’s list of hu­man uni­ver­sals is a list of psy­cholog­i­cal prop­er­ties which are found so com­monly that an­thro­pol­o­gists don’t re­port them. If a newly dis­cov­ered tribe turns out to have a sense of hu­mor, tell sto­ries, perform mar­riage rit­u­als, make promises, keep se­crets, and be­come sex­u­ally jeal­ous… well, it doesn’t re­ally seem worth re­port­ing any more. You might record the spe­cific tales they tell. But that they tell sto­ries doesn’t seem any more sur­pris­ing than their breath­ing oxy­gen.

In ev­ery known cul­ture, hu­mans seem to ex­pe­rience joy, sad­ness, fear, dis­gust, anger, and sur­prise. In ev­ery known cul­ture, these emo­tions are in­di­cated by the same fa­cial ex­pres­sions.

This may seem too nat­u­ral to be worth men­tion­ing, but try to take a step back and see it as a startling con­fir­ma­tion of evolu­tion­ary biol­ogy. You’ve got com­plex neu­ral wiring that con­trols the fa­cial mus­cles, and even more com­plex neu­ral wiring that im­ple­ments the emo­tions them­selves. The fa­cial ex­pres­sions, at least, would seem to be some­what ar­bi­trary—not forced to be what they are by any ob­vi­ous se­lec­tion pres­sure. But no known hu­man tribe has been re­pro­duc­tively iso­lated long enough to stop smil­ing.

When some­thing is uni­ver­sal enough in our ev­ery­day lives, we take it for granted; we as­sume it with­out thought, with­out de­liber­a­tion. We don’t ask whether it will be there—we just act as if it will be. When you en­ter a new room, do you check it for oxy­gen? When you meet an­other in­tel­li­gent mind, do you ask whether it might not have an emo­tion of joy?

Let’s go back to biol­ogy for a mo­ment. What if, some­how, you had two differ­ent adap­ta­tions which both only as­sem­bled on the pres­ence, or al­ter­na­tively the ab­sence, of some par­tic­u­lar de­vel­op­men­tal gene? Then the ques­tion be­comes: Why would the de­vel­op­men­tal gene it­self per­sist in a poly­mor­phic state? Why wouldn’t the bet­ter adap­ta­tion win—rather than both adap­ta­tions per­sist­ing long enough to be­come com­plex?

So a species can have differ­ent males and fe­males, but that’s only be­cause nei­ther the males or the fe­males ever “win” and drive the al­ter­na­tive to ex­tinc­tion.

This cre­ates the sin­gle al­lowed ex­cep­tion to the gen­eral rule about the psy­cholog­i­cal unity of hu­mankind: you can pos­tu­late differ­ent emo­tional make­ups for men and women in cases where there ex­ist op­posed se­lec­tion pres­sures for the two sexes. Note, how­ever, that in the ab­sence of ac­tu­ally op­posed se­lec­tion pres­sures, the species as a whole will get dragged along even by se­lec­tion pres­sure on a sin­gle sex. This is why males have nip­ples; it’s not a se­lec­tive dis­ad­van­tage.

I be­lieve it was Larry Niven who sug­gested that the chief ex­pe­rience hu­man be­ings have with alien in­tel­li­gence is their en­coun­ters with the op­po­site sex.

This doesn’t seem to be nearly enough ex­pe­rience, judg­ing by Hol­ly­wood scriptwrit­ers who de­pict AIs that are or­di­nar­ily cool and col­lected and re­pressed, un­til they are put un­der suffi­cient stress that they get an­gry and show the cor­re­spond­ing stan­dard fa­cial ex­pres­sion.

No, the only re­ally alien in­tel­li­gence on this planet is nat­u­ral se­lec­tion, of which I have already spo­ken… for ex­actly this rea­son, that it gives you true ex­pe­rience of the Alien. Evolu­tion knows no joy and no anger, and it has no fa­cial ex­pres­sions; yet it is nonethe­less ca­pa­ble of cre­at­ing com­plex ma­chin­ery and com­plex strate­gies. It does not work like you do.

If you want a real alien to gawk at, look at the other Pow­er­ful Op­ti­miza­tion Pro­cess.

This vi­sion of the alien, con­veys how al­ike hu­mans truly are—what it means that ev­ery­one has a pre­frontal cor­tex, ev­ery­one has a cere­bel­lum, ev­ery­one has an amyg­dala, ev­ery­one has neu­rons that run at O(20Hz), ev­ery­one plans us­ing ab­strac­tions.

Hav­ing been born of sex­u­al­ity, we must all be very nearly clones.