Monday, November 29, 2010

New blog

Content on this blog will remain unchanged, but please see my new blog, Signal Selection, for updated posts. 

Wednesday, November 17, 2010

Reproduction, altruism, and evolution

Haplodiploid sex determination operates within the hymenopterans, eusocial insect species used as living proof of Hamilton's theory of kin selection as an explanation for the origin of altruism.  But there are other eusocial species where this is not a factor, most notably termites and mole rats.  Why should these animals be apparently altruistic as well?  I can only conclude that haplodiploid sex determination is an incomplete explanation for eusocial kin selection and altruism.  It is hard to explain what a soldier termite gets from suicidal altruism, autothysis - it can only be that this self sacrificing behavior benefits kin selection all the same.  There are less extreme examples of cooperation, such as cooperative breeding - "if we work together, more offspring will survive to reproduce".  The Handicap principle is another explanation for altruism - "I can afford to be impressively wasteful with my resources, therefore I have better genes than most".  The Handicap principle is altruism as a demonstration of fitness, a signal, and not entirely for its own sake as it is with the soldier termite whose altruism is not a signal, or means to an end, but an end in itself!  "I die that the colony may live."  I think that any animal capable of using altruism as a signal can also use altruism for its own sake, but not vice versa, as signals require a certain level of cognitive ability to decode that not all animals possess.

Let's tackle this from another angle and change our perspective - consider the situation from the level of individual cells.  A multicellular organism such as a human is composed of billions of cells that are "born" and die, most of which are non-reproductive.  So we may easily consider eusocial species to operate as a super-organism, as the single organism and the single insect colony are largely similar.  Kin selection operates within my body just as it does clearly in the insect colony.  If an animal cannot physically reproduce, how is it any different from a non-reproductive cell within my body?  Each, colony and human, operates as the basic unit of sexual reproduction.  E.O. Wilson earlier made this same comparison.  Are my body cells therefore altruistic, just like the soldier termite?  I think so.  This analogy allows me to make the following proposition: altruism as an end in itself is something that primarily occurs within the basic unit of sexual reproduction, whereas altruism as a means to another end (as a signal, or handicap) primarily occurs between units of sexual reproduction.  Although some have suggested that humans are eusocial, that society forms a super-organism, we are no where near the borg-like eusocial insects, the hymenopterans and termites.  Our altruism is at least as well explained by the handicap principle as it is by kin selection.  (Besides, if you're helping someone closely related, is it really altruism?)  But more to the point I think kin selection and the handicap principle are capable of operating in parallel due to the different processes they affect.  Kin selection is natural selection, whereas the handicap principle, so far as altruism is concerned, is sexual selection (a special case of natural selection).

Tuesday, November 16, 2010

Sexual Selection

Over this last weekend I read Tor Norretranders' book The Generous Man: how helping others is the sexiest thing you can do. No, it wasn't because I was browsing the sex/self help section of the library. I found a reference to it after searching for more information about Zahavi and altruism online. (Another book about the evolutionary origins of altruism, The Altruism Equation, was not as engaging.) The main point Tor makes is that Darwin developed two ideas concerning the evolution of species: natural selection and sexual selection. Darwin published On the Origin of Species in 1859, but later published The Descent of Man and Selection in Relation to Sex in 1871. The second part of this second work contains 550 pages about sexual selection. (This is something I really should read.) Zahavi's work a hundred years after Darwin's publication of his ideas spurred a re-examination of the field, which has produced an ever-accelerating number of theories.

Tor makes the case that as humans, we owe what makes us truly unique among species to the process of sexual selection, which operates according to Zahavi's Handicap principle; natural selection alone could never account for humanity. The first part of the book seemed to confirm much of what I already knew. Part of the fun was recognizing the names of scientists that I had come across before and seeing them joined together in common cause to elucidate a single idea between the covers of one book. But the last few chapters contained some interesting predictions. Take this one for example: "Computers and robots will have to learn about hau, about generosity, and in the final analysis, about sex." (p293). Definitely thought provoking!

Tor is a Danish author of books about science and its role in society.  The Generous Man was published in 2002 and later translated into English in 2005 after enjoying success in Europe. He writes in an easy to read and engaging style. The book is basically an homage to Zahavi's Handicap principle as it applies to sexual selection and altruism. And that is what makes it GREAT! He applies the concept to ideas that even Zahavi might be reluctant to pair it with, but that is all part of the fun.

Wednesday, November 3, 2010

Amotz Zahavi

I haven't forgotten the importance of Amotz Zahavi's contribution to our understanding of evolution, which I only mentioned in passing earlier.  Evolutionary concepts are fascinating when one realizes the powerful and wide ranging implications they have.  Take for example Gould's paper "The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme" (1979) or Trivers paper "Parent-Offspring Conflict" (1974).  To these add Zahavi's "Mate selection - a selection for a handicap" (1975). 

Amotz Zahavi elaborates this theory even more in his book The Handicap Principle: a missing piece of Darwin's puzzle.  Specifically in chapter 12 "Babblers, competition for prestige, and the evolution of altruism", he demonstrates that when an animal acts altruistically, it handicaps itself - assumes a risk or endures a sacrifice - not primarily to benefit its kin or social group but to increase its own prestige within the group and thus signal its status (and fitness) as a partner or rival.  "Altruistic acts obviously demonstrate - and are perceived as demonstrating - the abilities of those who perform them." (p225) 

What does this say about religion, which may be a handicap itself?  Or Aristotle's virtue of magnanimity, or Guy Laliberté (known for throwing the best parties), or romantic overtures (whose goal is often copulation)?  I think it sheds light on all of them.

It is interesting to note that the two competing theories explaining the origin of altruism are Zahavi's Handicap principle, and W. D. Hamilton's "kin selection" theory.  It appears that Hamilton's theory is more popular among evolutionary biologists, although it is not without problems.  The subject remains unresolved.  Here is a video of Arabian babblers, and a lecture by Zahavi.