From: barkow@ac.dal.ca
Newsgroups: sci.anthropology
Subject: BREASTS AND EVOLUTION
Date: 25 Aug 92 19:57:35 -0300
Organization: Dalhousie University, Halifax, Nova Scotia, Canada

It is rather embarrassing to cite one's own work but I don't
have anyone else's stuff on disk.  The debate over the evolution
of the permanently enlarged female human breast is an on-going
one and the paragraphs below at least illustrate that point.
Presumably, large breasts and concealed ovulation (the
replacement of the usual primate estrous cycle with a menstrual
cycle) evolved for related reasons.  The material below
discusses the work of physical anthropologist Sue T. Parker, who
assumes that our distant ancestors engaged in chimpanzee-type
communal mating and that males seek to control female sexuality.
The important question here is that enlarged breasts mean
pregnancy, not fertility, among our relatives, so how is it that
many human males find breasts sexually attractive?  For those
who want some bibliography, most university libraries have the
book from which the excerpt is taken (see especially the
footnote on p. 340).  I would suggest a look at Helen Fisher's
new book on sex differences, as well (though I haven't seen a
copy yet, myself).



_______________________________
| Jerome H. Barkow            |
| Department of Sociology     |
|  and Social Anthropology    |
| Dalhousie University        |
| Halifax, Nova Scotia        |
| Canada B3H1T2               |
| Office: (902) 494-6747      |
| INTERNET = BARKOW@AC.DAL.CA |                 
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-------------------------------





Excerpt from: 
Barkow, Jerome H.  1989.  Darwin, Sex, and Status: Biological Approaches to
Mind and Culture.  Toronto: University of Toronto Press, pp. 339-340.



     Breasts. Parker accepts an argument that appears to have originated with
Desmond Morris (1967:62) concerning the sexual significance of large breasts.
Smith (1984), however, makes the point that large breasts could not have
evolved back during our hypothetical period of communal mating.  Selection
would have favored males who were not attracted but repulsed by large 
breasts, since they would have been a sign of pregnancy or  lactation -- and
therefore of the female's not ovulating. Smith (p. 641) suggests that they
evolved later.

     But even after we no longer mated communally, why should large breasts
have evolved? Smith believes they were selected for  as a means of confusing
males about a female's lactatory and  therefore ovulatory status, in order to
circumvent male control  over female sexual activities. To the extent large
breasts are  now a sexual attractant, he argues, this development would have 
occurred only after they had already become firmly established.  Smith does
not, however, explain why the swollen abdomen of  pregnancy, like the enlarged
breasts, did not also become a  permanent female secondary sexual
characteristic. Nor does he  account for breasts becoming sexually attractive.

     Neither Smith nor Parker discuss the argument made by Cant  (1981) and by
Mascia-Lees, Relethford and Sorger (1986) that the  breasts enlarged initially
because they were storage areas for  fat. Presumably (though this is not part
of Cant's argument),  storage in this region could have been selected for only
after  the ending of communal mating. Since pregnancy and lactation make 
heavy physiological demands upon the body, large breasts would  have been
reliable indicators of female ability to bear young  successfully. Males would
therefore have been selected to prefer  females with enlarged breasts. Such a
preference would in turn  have resulted in the sexual selection of females who
tended to  have (deceitfully) large breasts even when their fat reserve 
levels were low. We might then amend Parker's scenario with  regard to breast
enlargement in this manner: Large breasts  evolved only after the ending of
communal mating and because (a)  they were a site at which to deposit adipose
tissue (that is, to  store fat); (b) males were selected to prefer large
breasts  because these indicated a nutritional reserve; (c) females were  then
selected for relatively large breasts even when this reserve  was low, and
(arguably) also (d) because the enlarged breasts  confused males about
ovulatory status and so weakened male  control over female sexual activity.
Newsgroups: sci.anthropology