A new paper published in Philosophical Transactions of the Royal Society B by a group of University of Nebraska at Omaha (UNO) scientists has clearly shown that 'science' has no rigid proscriptions for what male and female roles are or what they should be in nature.
In a recent interview on Fox News, conservative political blogger Erick Erickson responded to a recent Pew survey (that showed in 40 percent of American households with children, women were the major breadwinners) by stating that it was "anti-science" for society to accept this role for women. "When you look at biology, when you look at the natural world—the roles of a male and a female in society and in other animals, the male typically is the dominant role. The female, it's not antithesis, or it's not competing, it's a complementary role," Erickson said.
The UNO group, led by Jeffrey French, Varner professor of Psychology, Biology and Neuroscience at UNO, reviewed the published literature on species of mammals (the taxonomic group to which human beings belong) in which females are not only more aggressive than males, but in many cases are socially dominant over males.
"In a host of species, females are clearly dominant to males in feeding competitions, in access to preferred locations for resting and sleeping and in many other facets of social life," French said. Species in which females "rule the roost" include spotted hyenas, rock hyrax (a close relative of elephants), ring-tailed lemurs, marmosets and hamsters.
In the paper, The influence of androgenic steroid hormones on female aggression in 'atypical' mammals, French and his group, which includes graduate students Aaryn Mustoe and Jon Cavanaugh and research technician Andrew Birnie, present information on the biological origins of this sex-reversed pattern of dominance and aggression. In many cases, exposure to high levels of androgen hormones (like testosterone) during gestation or shortly after birth can 'program' the brain centers involved in regulating aggression and dominance in females, thus shaping the nature of aggression later in adulthood. Additionally, the ability to form complex coalitions among females, particularly among related individuals (mothers, daughters and granddaughters) can provide an important social route to female dominance in some species.
"In contrast to Mr. Erickson's characterization of male and female roles, our work shows that simply having XX or XY chromosomes (the sex-determining chromosomes in female and male mammals, respectively) does not dictate what an individual's social role, social status or aggression level will be," French said. "Evolution has shaped multiple manifestations of sex roles in mammals, and our review shows that many of these differences have, at their root, hormonal mechanisms. This includes diversity in sex differences in patterns of dominance and aggression, including many cases where females are both more aggressive and more dominant than males."
For more information, contact Jeffrey A. French at firstname.lastname@example.org or at 402.490.1256.
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