07/09/2010 03:15 pm ET Updated Nov 17, 2011

Dealing with Gender

Defining who is a fair competitor in athletic contests of males or females remains a difficult issue. Our understanding of sexual development and identity is evolving along with our ability to test and measure the process.

The question is, should we outlaw certain people from competition whose gender is difficult to categorize?

Sex determination is a very complex process that involves many levels of regulation, and yields a spectrum of traits (phenotypes) that fall within the range of "normal." In addition to its genetic makeup, a fetus is exposed to many signals that affect its strength as an adult, including hormones, environmental factors, and the nutrition absorbed from its mother's food.

Success in a long jump competition, for example, can be traced to how your muscles are configured, your genetic makeup, and the environment you and your mother experienced when you were an embryo.

Even though humans have less fluid sexual traits than many other species (many fish, for example, can change sex in adult life), we nonetheless expect to see a range of sexual characteristics and strengths in people.

For example, you could have a genetic female, someone with two X chromosomes and no Y chromosome, who functions as a female, but she might have partially masculine genitalia because she experienced high concentrations of adrenal steroids as an embryo. These same steroids may have acted on developing muscles to increase their strength capacity.

This person may have a vagina, act as a female in a sexual relationship, and have a body that supports pregnancy -- all measures associated with "femaleness." Yet the chance combination of her genetic makeup and factors that influenced her development have produced an individual with extraordinary athletic capabilities.

Should she be outlawed from competition because she lies at an extreme end of the spectrum of females?

Isn't the point of competition to find the most gifted individuals?

People who, because of the influence of their genes or their developmental environment, extend the limits of human ability give us the hope and admiration we have for the best athletes -- that we can all reach for the stars. I realize that we have to decide whether it is fair to let a person at the far end of the female range compete as a woman. But that decision can be a very tricky business.

I think the Caster Semenya controversy has been sullied by innuendo -- rumors about the athlete's intention to pretend that she is a female. I have not seen any medical assessments, but this remarkable athlete may simply be at one end of the bell curve of "femaleness." Even with a battery of tests to assess chromosomes, hormones, and physical characteristics, it may be very hard to draw a line - and wherever we draw it, we may eliminate people in the range of human ability that we find so inspiring among the world's athletes.