Ryan Schacht, Utah – Sexual Ratios

The nature of your surroundings might dictate your desires.

Ryan Schacht, post-doctoral research fellow at University of Utah, is studying our reproductive goals in relation to availability.

Ryan Schacht‘s research explores variability in behavior within and between groups. Currently, Ryan is studying how people make reproductive decisions and how individual and contextual differences influence behavior. For example, what are the traits people look for in partners? What types of relationships do people pursue? How do social norms influence these decisions?

Through his work, he questions generalizations about human behavioral universals that have arisen from research conducted primarily on Western populations and conventional assumptions regarding gender differentiated behavior.

His dissertation research was conducted over a sixteen-month period across eight Makushi communities in Guyana, South America where he used a combination of surveys and ethnographic methods to assess partner choice preferences, relationship styles, parental investment and social norms driving expectations of men and women within a relationship.

Sexual Ratios

Popular wisdom and common evolutionary arguments hold that the sexes seek fundamentally different relationships: men want short-term, uncommitted flings, while women seek longer-term, loyal partnerships. The explanation for this generally comes down to fundamental differences between men and women. Women invest more in reproduction than do men. They conceive, gestate and breast-feed babies. So being picky is important for women because choosing poorly can lead to going it alone.

For men, reproduction may require no more investment than a brief sexual encounter – there are potentially no long-term costs.

However, a developing theory challenges these sexual stereotypes. According to mating market theory, relationship preferences are not expected to follow standard expectations. Instead, what men and women want should be influenced heavily by the availability of partners. If we think of the number of men and women in market terms, economic principles of supply and demand apply.

The rarer sex has more bargaining power in the marketplace. For example, when there are extra women, men face a favorable market and can behave promiscuously. They don’t have to invest much in being a loyal partner or father. However, when women are in short supply, they can demand faithfulness and commitment, and men meet those demands because women are scarce and therefore a valued resource.

To evaluate these ideas, we worked with the Makushi people of southwestern Guyana. We interviewed 300 men and women in eight communities with differing ratios of men to women. We asked about their relationship preferences using a standard psychological survey. We found that when women were abundant, men were the fling-seeking cads we stereotypically expect them to be.

However, when men outnumbered women, men’s interest in short-term relationships waned. In fact, in the communities with the most men, men’s and women’s preferences were indistinguishable. Both wanted committed relationships. These findings also may apply to people in western societies. Wherever the male-female ratio varies, so will the availability of partners and the kinds of relationships people want.