In sich sexuell vermehrenden Arten müssen komplexe Adaptationen fast universal sein. (zumindest in einem Geschlecht; natürlich kann es gravierende Unterschiede zwischen Männern und Frauen geben,
was ja in der Tat der Fall ist was natürlich nicht auf Homo Sapiens zutrifft, sondern nur auf alle anderen bekannten Spezies.)
(Ich weiß nicht, warum das Folgende nicht für asexuelle Arten gilt, aber ist auch nicht so wichtig.)
Wenn für eine Adaptation 6 Gene notwendig sind, und jedes von ihnen nur zu 10% in der Population vorkommt, dann tritt diese Adaptation nur in einem von 1Millionen Organismen auf, und die durchschnittliche Fitnesssteigerung ist vernachlässigbar.
Erst wenn Gen A, B, C, D, E schon fast universal sind, ist es möglich, dass auch Gen F, das nur in Kombination mit diesen Genen von evolutionärem Vorteil ist, eine starken evolutionären Vorteil mit sich bringt, somit hohem Selektionsdruck ausgesetzt ist, und sich in relativ kurzer Zeit ausbreiten kann.
Daraus folgt, dass wir Menschen einander sehr ähnlich sein müssen, und wenn man die Liste universaler menschlicher Eigenschaften (von D.E. Brown) durchforstet, wird diese Hypothese auch bestätigt.
Ich bin zwar nicht besonders bewandert in evolutionärer Biologie, aber die Kommentare von Razib Khan und Tim Tyler entkräften, meiner unbedeutenden Meinung nach, Yudkowsky’s These einer angeblichen “psychologischen Einheit der Menschheit”:
hm. there’s a lot to this…but let’s just say that when it comes to *psychology* the residual of non-universality seems really important to focus on in the area of individual differences. specifically, it seems entirely possible that frequency dependent personality morphs abound; e.g., all the stuff about drd4 that i’ve been posting on my weblog. of course, this is single-locus, but i think it’s just the locus of biggest effect. i suspect that what evolutionary psychology misses is that after you account for the substrate of human universals you’ve got personality morphs which are playing “games” with each other, and in particular there are a host of low frequency morphs running around. these morphs are “complex” to my way of thinking, though perhaps not complex in the way you’re implying (i know the evo psych argument against a lot of variation on traits). i happen to think epistasis might also be pretty significant in the transient.
second, i’m also getting curious about variation in traits we perceive as on-off, where those who are “off” are purely pathological. e.g., it turns out that 2% of the population might be “face blind” but have been cryptic because they develop techniques to mask this problem and don’t talk about it. i don’t think it is just a 2% vs. 98%, i think there are a few other steps “in between”, though there’s a skewness toward the “normal” facial recognition ability side. on the basis of this i’m willing to dig a little deeper into “human universals” to see what might crop up on the margins.
The theme of this post isn’t very accurate, as large phenotypic polymorphisms in various other species demonstrate – e.g.:
From a strategic point of view we are especially interested in those species that have two kinds of males. It’s almost like having a third sex. In fact the winged males look far more like females than they look like wingless males. Both females and winged males are almost believable as wasps, although they are tiny. But the wingless males are nothing like wasps to look at. Many have savage pincer jaws which make them look a bit like miniature earwigs going backwards. They seem to use these jaws only for fighting â€” lacerating and slicing to death other males that they encounter as they stalk the length and breadth of the dark, moist, silent garden that is their only world. – Climbing Mount Improbable, Richard Dawkins.
Where did the reasoning go off the rails?
It isn’t just the case of males and females where different alleles can form a truce. There’s the whole phenomenon of frequent-dependent selection. Most people are familiar with this from blood types, and sickle-cell anaemia. Alleles with phenotypic effects involving disease resistance can be advantageous when rare and disadvantageous when common – resulting in them never going near extinction or fixation.
Also, this premise is inaccurate:
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.
Gene B can spread if gene A is present at a frequency of 20% in the population – provided it is not deleterious in the absence of gene A. Sure, then the selection pressure maintaining it is reduced by a factor of five, but that’s not necessarily enough to kill it off.
Finally, phenotypic variation does not necessarily depend on genetic variation. There’s also the influence of the environment to consider. In general, the environment is quite capable of sending some organisms down different developmental paths depending on the circumstances in which they find themselves. This is known as phenotypic plasticity.
There are plenty of examples of phenotypic plasticity in humans – e.g. the effect is an important part of the reason why a Sumo wrestler and a racing jockey have different phenotypes.
Tim Tyler again (fast zwei Jahre später):
The supposed psychological unity of human kind seems to be part of the “CEV” idea – since it suggests the intersection of human desires might be large.
However, if humans frequently want conflicting things – due to them all wanting to selfishly promote their own ends – the intersection of all human desires seems as though it would be smaller and of less interest.
CEV scheint mir der schwächste Punkt in Yudkowsky’s Weltanschauung zu sein. Viele der Top-Commenter sind ebenfalls anderer Meinung als Yudkowsky was CEV angeht.
(Wedrifid geht sogar davon aus, dass es nichts weiter als ein gelungener Marketing-Trick ist. Scheint unwahrscheinlich, aber man weiß ja nie.)
(On a more personal note: It looks like my contempt for hypocrisy exceeds my hatred of violence and suffering. E.g. psychopaths like Bridget Gregory (Last Seduction) or Mickey and Mallory (Natural Born Killers) seem to me less despicable than hypocritical signaling-machines gone wild, like, um, 90% of all humanity. I don’t think that’s a common trait, but it’s of course possible that after reflection, increased intelligence, etc. I (or humanity) will see the light. OTHO, hypocrisy is one of the defining traits of our species, which makes me less optimistic about CEV, to put it mildly. )