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.