Unit of selection (in defense of "group" selection)

arlin at ac.dal.ca arlin at ac.dal.ca
Sat Jan 15 13:13:42 EST 1994


In article <2h5hu4$mmr at news.u.washington.edu>, mpmartin at u.washington.edu (Michael Martin, esq.) writes:
> that I haven't).  While it is true that the gene and the individual are 
> now seen as the most likely units of selection (the "selfish gene" idea 
> of the gene as the unit of selection is essentially the same as the idea 
> of the individual as selection with a few minor but important 
> differences), it has been close to a decade since any serious evolutionary
> biologist has seriously considered the possibility of "group selection."

Michael Martin is probably correct to the extent that "no serious
evolutionary biologist" today believes the fanciful proposal of
Wynne-Edwards (that pervasive group selection results in communities of
species that restrain their reproduction in such a way as not to stress
their non-specific comrades, explained in his 1962 book _Animal Dispersion
in Relation to Social Behavior_).

However, the failure of community-level group selection to create a happy
gaia-world and make us love and cherish other species should not be taken as
a general reproach to all attempts to consider supra-individual selection.
Natural selection at levels of organizational higher than that of the
individual is an entirely logical extension of individual selection, and it
cannot be ruled out on theoretical grounds, therefore it should not be
dismissed lightly.  For a brief recent discussion of this issue, see 
chapters 2-4 of

Williams, G. C.  1992.  _Natural Selection: Domains, Levels, and
Challenges_ (Oxford Univ. Press; ISBN 0-19-506933-1).

in which a theoretical framework for considering levels of selection is
developed, and the evidence for specific types of clade selection (e.g.,
against large body size, or against loss of sexual reproduction) is
discussed.

Arlin Stoltzfus 
Dept. Biochemistry 
Dalhousie University



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