266 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”own genes. Hamilton’s idea is called “kin selection theory” or “inclusive
fitness theory.”
Hamilton’s equation was taken as the rule for many years, until the
genetic makeup of termites came to light in the 1990s. It was found unex-
pectedly that termites, which are incredibly successful eusocial insects
like bees and ants, are actually diploids rather than haplodiploids. In other
words, all members of a termite colony, male and female, are uniformly
diploids, so the relatedness of a sterile worker to a sibling and to a daugh-
ter are no different (both being ½). Furthermore, it is now known that
there are many haplodiploid insects that do not live in a eusocial struc-
ture. Hamilton’s idea became problematic — haplodiploidy is neither a
necessary nor sufficient condition for eusociality, though it may be a con-
tributing factor. Recently, D.S. Wilson and E.O. Wilson pointed out the
inadequacy of Hamilton’s theory, which is based on selection at exclusively
individual level, and proposed to replace it with a dynamic mechanism
based on selection at the group as well as individual levels — called mul-
tilevel selection.^9 In short, the success of social insects is the outcome of a
combination of group and individual selections. Altruism plays an impor-
tant role in group selection as well as kin selection. As Wilson and Wilson
suggested, within the same group, selfish members survive better than the
altruists; but in a competition between groups, those with altruist mem-
bers fare better than those without.10,11 Interestingly, this is essentially the
revival of Darwin’s original idea laid down in The Descent of Man in 1871.
In learning the lesson from social insects, we must not forget that
their group behavior is stereotyped and genetically programmed, with
very little individual variation. They rely on group rather than individ-
ual identity. Their social determinants are mainly odors (pheromones),
carried by a group of volatile, small hydrocarbon molecules produced
endogenously or acquired from the environment (over twenty of these
are known for ants). An odor, or an orchestration of odors, defines a caste
status and nest identity. When two ants come in contact, the odors they
“wear” can tell a friend from a foe, and the outcome is a matter of life
or death.