"you are unable to explain to a competent person why you believe what you believe."
I'm trying to be patient here, but I don't know how much better I can explain this. You either get it, or you don't. If you don't, you're not as competent as you believe; you either don't really understand the basic concepts we're talking about or have mental blocks when it comes to applying them to humans, and this is something you need to deal with yourself.
No matter how many times I explain this, you don't want to get it. Your starting point is that Salter can't be right; so when I explain to you how your reasoning is flawed, regardless of how many times we go through this or how many times I address a particular objection, your response is just to throw out additional confused reasoning, often forgetting things you previously agreed I was correct on and switching back to objections that have already been addressed.
The benefit of the ethnocentric altruism alleles comes from between-group selection, not within-group selection. Even in the first generation, an allele for ethnocentric altruism can potentially boost its odds of representation in future generations by, for example, reducing the chance of extinction of the group it's found in (whether by contributing to avoiding defeat and extermination by rival groups in an ancestral environment, or resisting replacement-level immigration in the modern world).
It makes no difference whether there is enough between-group relative to within-group competition at modern scales to maintain or grow this sort of variation in the long run (and certainly Hamilton speculated that self-sacrificing altruism would be found at higher levels in tribal people than in the long-civilized). In a particular instance of intergroup competition of the sort we're discussing, ethnocentric altruism alleles attuned to Hamilton's rule would by definition be adaptive.
This will always be true, regardless of scale, and regardless of how often the group is actually faced with the threat of intergroup competition. In the face of such a threat, the alleles (ones that enhance group competitiveness in a generalized fashion and are sensitive to cost, benefit, and relatedness) will be adaptive.
Your argument is somewhat analogous to claiming sickle-cell alleles can't be adaptive (or even exist in the first place!) in a malarial environment because their frequency would not increase in the long run in the absence of malaria. Even if malaria is nearly wiped out and the frequency of sickle-cell alleles begins to decline, this does not prove that if a mosquito with malaria does land on you you'd be better off not having a sickle-cell allele.
"Yes, the behaviors are polygenic. But all genes have to start at low frequency, and you have not explained how they get to high frequency"
Again: positive selection will come from intergroup competition. If your argument is that all relevant variants would be snuffed out immediately, leaving no variation on which group-level selection could act, this is of course absurd. Yet again: we're talking about very large numbers of weakly-selected variants, and a large surface on which new mutations can arise.
Crow and Aoki modeled group selection for polygenic behavioral traits. Again, it boils down to Hamilton's rule.
Group selection for a polygenic behavioral trait: a differential proliferation model [pdf]
Group selection for a polygenic behavioral trait: estimating the degree of population subdivision [pdf]
Our general approach is to use molecular markers, which are selected very weakly at most, as neutral indicators of population structure. GST gives us an appropriate description of the relevant aspect of the structure. By using Eq. 3 we can state the maximum value of cost/benefit of a quantitative trait if that trait is to increase in average value or frequency in the population. GST describes the present structure of the population; it does not tell us how it got that way. If this value has been roughly stable in the past, we could expect that traits with c/b up to this value would have increased in the population, assuming of course that such traits exist and have heritability greater than zero.
Empirically, ethnocentrism exists, and no doubt has since before we were humans. Empirically, ethnocentrism has heritability greater than zero.
Nature, nurture, and ethnocentrism in the Minnesota Twin Study [pdf]
Common Heritable Effects Underpin Concerns Over Norm Maintenance and In-Group Favoritism: Evidence From Genetic Analyses of Right-Wing Authoritarianism and Traditionalism [pdf]
- Genetic evidence for multiple biological mechanisms underlying in-group favoritism [pdf]
Your issue is with reality, not with Salter or me.
"Of course, ethnic altruist genes could be maladaptive relics of the past, when groups were small. But Salter says they are adaptive now."
Again, see above.
And Salter never claims we are well-adapted to ethnic competition in the modern world. If he'd believed that to be the case, he would have had little reason to write the book. From the introduction:
On Genetic Interests is an attempt to answer the empirical question: How would an individual behave in order to be adaptive in the modern world? I adopt the neo-Darwinian meaning of adaptive, which is to maximize the survival chances of one’s genes. I begin by describing humans as an evolved species and thus as creatures for whom genetic continuity consists of personal reproduction or reproduction of kin. [. . .]
Humans can no longer rely on their instincts
There is nothing immutable or necessarily perfect about adaptations or the understanding, appetites and preferences they organize. Natural selection is constrained by evolutionary history and environment. It shapes bodies and behaviours in small increments by modifying existing species. Much in nature is badly designed, if one examines it from an engineer’s viewpoint. [. . .]
Like adaptations that advance them, proximate interests can be imperfect in promoting genetic interests. The main problem is the slowness of natural selection compared to the rapidity of technological and social change since the Neolithic. The inertia of adaptations can cause them to continue to promote proximate interests that no longer serve fitness. For most of humans’ evolutionary history, adaptations tracked slow-moving environmental change, including technological advances. In the species’ distant hominid and pre-hominid past, proximate interests that reduced an actor’s fitness were valued less and less as the genes that coded for such valuation failed to reproduce. For this reason, at most moments in time proximate interests have correlated with ultimate interests because the environment has changed so slowly that physiology and behaviour could keep track with it. Proximate and ultimate interests have been in equilibrium except where rapid changes in environment occurred. The equilibrium applying to humans has been upset in recent generations, so that we can no longer rely on subjectively designated proximate interests to serve our ultimate interest. We must rely more on science to perceive the causal links between the things we value and formulate synthetic goals based on that rational appraisal.
Proximate interests, often reflected in consciously held values, have become increasingly fallible guides to ultimate interests because modern humans live in a rapidly changing world. Humans evolved in small bands consisting of a few families, sometimes grouped into tribes numbering in the hundreds. For most of their evolutionary history humans made a living by hunting and gathering in largely natural environments. They lacked formal organization and hierarchy. Adults coordinated activities by negotiating simple demographic role specializations — by age and sex — on an egalitarian basis with familiar band members. Most information was common. Humans now live in societies numbering in the millions where the great majority of interactants are strangers or acquaintances. They make their living through a great diversity of occupations resulting in radical asymmetries in information. They live and work in largely man-made urban environments. They are formally organized into states administered by extended hierarchies of rank and resources actuated by authoritative commands, impersonal contracts enforced by the state authority, and powerful forms of indoctrination performed by universal education, centralized media and entertainment.
However, to the extent we are able to correctly reason about what would be adaptive in the context of intergroup competition, and act in accordance with this, we have the equivalent of our generalized ethnocentric altruism alleles.