Thank you,my friend @litguru! If you look at the comments here you will see disagreements continue. That's wonderful. When a blog, a science blog, becomes a forum for discussion: that's ideal.
You are kind, and I will continue to read about Wallace. A fascinating discussion.
It looks like disagreement in the forum is on how much credit Wallace should get. I was referring to the idea of whether or not natural selection applies to humans. When it comes to disagreements on the theory itself, it's research and experimentation that can settle the matter. The theory of natural selection as first espoused by Darwin was based on direct selection- the notion that individual traits raise that individual's reproductive success. The theory, however, has undergone a few mutations to account for some complex behaviors that perhaps Darwin was not familiar with at the time of publication. We know that altruistic behavior exists, in which animals including humans use resources for the benefit of non-descendant relatives, but which eventually may (indirectly) benefit an individual's fitness. This is a form of evolutionary selection called indirect selection, which contrasts with direct selection- the idea that individual traits confer the advantage.
Marshall Sahlins (1976) critiqued the idea that indirect selection applies to human by discussing the issue of adoption in islands of the South Pacific. Cultures in that region are big on adoption so that up to 30% of children are adoptees. Sahlins argued that given that people adopted children who were not their kin, then evolutionary theory did not apply to understanding this behavior. He (mistakenly) thought that indirect selection was the only theory that could be applied in this case, and he was not aware that research on altruism had several possible explanations for the adoption case in Oceania. Moreover, the theory of indirect selection did not necessarily require that the adoptees were closely related in order to raise the fitness of the adopting parents. It only requires that they be genetically related.
An analysis conducted by Joan Silk of 11 cultures in Oceania showed that adoptions in the region were not genetically random (as Sahlins had surmised). The majority of adopters and adoptees were genetically related. Adopters tended to adopt cousins, nieces, nephews, etc. In other words, the process of adoption was not unselfish and random, as Sahlins believed, but was motivated by the fitness gained by the adopters. This provided support for the theory of indirect selection and is evidence that natural selection is at work in humans.
We know that people in that region also adopt non-genetically related children. So, how does natural selection deal with this? Adopted children could contribute to the family and thus raise the fitness of the adopters. This leads to the hypothesis that a family with few or no children would be more likely to adopt children, who would then help with the family work. An analysis by Silk showed that indeed small families tended to adopt children more frequently than large families. Thus, providing further support for the theory of natural selection in humans.
There is more to this than what I have outlined here, but the key point is that when it comes to settling the argument about whether natural selection applies to humans, as Darwin conjectured, or not, as Wallace believed, the issue needs to be settled in the realm of scientific research and analysis. Easier said than done when you start dealing with topics like monogamy, polygamy, coercive sex, etc.
Resources
Sahlins, M. 1976 The use and abuse of biology. University of Michigan Press, Ann Arbor.
Silk, J.B. 1980. Adoption and kinship in Oceania. American Anthropologist. 82: 799-820.
Silk, J. B. 1990. Human adoption in evolutionary perspective. Human nature 1: 25-52.
John, A. 1993. Animal Behavior: An evolutionary approach. Sinauer associates, inc.
Finally I have had time to put everything aside and focus on your informative reply. Funny thing is, it never occurred to me that natural selection did not operate with humans. I see you enlist valid studies to support that view. My 'opinion' is more casual than that, and therefore less valid.
I think I feel this way for several reasons:
However, I am fascinated by your research. If you don't write a science blog about this, I may have to. Always my blogs are driven by curiosity. Questions, such as this one, arise and I want to know more.
Thanks for taking the time to share this with me.
I'm in agreement with you that it seems to me that the same rules would apply to all of us, but this topic is mine field of controversy. The issue is that human behavior is extremely complex when compared to that of a non-human animal. So, it's hard to get clean data out of humans. If I wanted to study human mating behavior, I would not be able to get ethics approval to put secret cameras in people's bedrooms to see how they behaved sexually in their natural environment. This would not be a problem, if I wanted to study squirrels. :)
Don't tempt me, or I may yet take a bite of that fruit.
Please do?!!!
I might just do it. Natural selection can be a dry subject, but if I can find a way to add a little spice, I'll be on it quicker than you can say survival of the fittest for reproductive success.
Oh yeah, just add an affair or something, or a perchant for wierdness. it'll be great.