According to Brown University Prof. Anne Fausto-Sterling, the belief that genetics alone can determine a person's sexual orientation is a "poor and misleading account of what genes do and how they affect us." Instead, Fausto-Sterling explained that genetic factors interact with other social and environmental influences in people's lives to determine their sexual identities.

"Genes are not at the bottom of the pyramid," she said, "but they are in the middle of the sandwich."

Fausto-Sterling, professor of biology and gender studies, challenged common misconceptions about sexual development in the Women's and Gender Studies department's annual Eleanor Roosevelt presentation last Wednesday, "Nature, Nurture, Neither: Reconceptualizing Gender and Sexuality."

Fausto-Sterling claimed that sexuality and developmental differences between genders are based on systems in which both nature and nurture interact.

"Rather than being determined by genes or experiences, [sexuality] results from complex interactions between system components."

As opposed to a commonly held view that nature and nurture are completely isolated factors, Fausto-Sterling explained that "nature and nurture are components of a single dynamic system."

Using the example of someone learning to walk, Fausto-Sterling described the nature-nurture interaction.

Walking "can be disrupted in different ways depending on the system," she said.

"You are going to be walking differently on sand than on a peat bog or hard concrete. The muscles which you use will be different and the way you stabilize yourself will be different."

Similarly, a person's sexual identity will develop differently because of his or her interactions with a specific environment.

Fausto-Sterling emphasized that scientists shouldn't consider DNA alone in discussing the development of sexuality.

She explained that genetic factors act in conjunction with environmental components.

"The major point here is that DNA is an inert, uninteresting substance," she said during the Q-and-A period, eliciting laughter from the audience.

"What's really interesting is not so much what genes you have, but what genes are expressed."

As a person develops, his or her social experiences cause certain genes to become more influential than others.

"Genes must get expressed as we experience the sensory world," Fausto-Sterling said. "What gets expressed and when and under what circumstances is the critical question."

Considering the inextricable link between genetic and environmental factors, Fausto-Sterling denounced the explanation of homosexuality as either genetically determined or an individual choice.

"You can't think of a worse way to frame the problem," she said.

Fausto-Sterling said the main flaw in the argument that homosexuality is based on a personal choice is that it implies that a person has conscious control over sexual identity.

During the Q-and-A, one student brought up recent experiments conducted at the University of Illinois at Chicago in which scientists isolated a gene for homosexuality in fruit flies, leading some to conclude that homosexuality is based solely on genetic factors.

Fausto-Sterling responded by explaining that this theory cannot be extended to humans.

"The definition of sexuality in animals is different to humans because sexual desires in humans move far beyond that narrow biological paradigm," she said.

Fausto-Sterling described her experiments, in which she applies her dynamic systems theory to study gender differences in the development of vocalization and motor skills.

Throughout the experiments, she observed that in certain stages of infancy, a mother tends to speak more to the girls and make playful noises at the boys.

She suspects that this may be a factor in girls' development of more advanced vocalization skills than boys, but said that no definite claims can be made.

Ari Salinger '12 thought Fausto-Sterling's experiments on gender differences needed a larger sample size for the results to be considered scientifically valid.

"It's a really great and substantial idea, however I think it's going to take a lot more research before it becomes something more finite," he said.

Salinger continued, "She didn't take into account many things such as paternal studies and cross cultural studies."

Prof. Jim Mandrell, chair of the Women's and Gender Studies program, didn't consider the experiment's small sample size to be a problem, given the intentions of the experiment.

"In her presentation she made it clear that she couldn't make large social claims from a smaller sample size."

He explained that he viewed the experiment as a starting point that will provide direction for a larger experiment on developmental differences between genders.

Some students in the audience found it was difficult to follow Fausto-Sterling's scientific discussion.

The presentation "was very scientifically based, which was difficult to understand for people more into the social sciences," said Sara Steinhouse '12, "but when she got into the sexuality aspect it become more accessible, and as a result more interesting."

For those audience members already familiar with Fausto-Sterling's work, it was exciting to hear the professor explain her experiments on sexual development.

Students in the University Writing Seminar "Gender and Sexuality" learned about Fausto-Sterling's theories and experiments. Said Mariah Henderson '12, "It was really cool to get to hear her in person.