Is homosexuality a conscious choice made during the course of one's life, or is it caused by quantitative genetic differences? Is looking for biological causes unnecessarily justifying a lifestyle which requires no justification?

These and other questions were debated at a Saturday symposium held at the Medical School on the biological and physiological nature of homosexuality.

Many speakers at the conference seemed to argue that homosexuality is at least in part biologically determined, presenting data from their own and others' experiments supporting the theory.

The conference, attended by more than 200 scientists and Boston area students, was an annual symposia sponsored by the Kinsey 2-to-6ers, the gay, lesbian, and bisexual student association of the Medical School.

Eight doctors and professors specializing in psychiatry and genetics presented data and opinions on the subject.

"We're engaging in a discussion that some people say ought not even be engaged in," said Dr. Marshall Forstein, an instructor in psychiatry at the Medical School, during his introduction. All of the speakers addressed the question of whether such discussion was necessary or ethical.

Second-year medical student Eddy Machtinger, an event co-organizer, said the topic should be discussed to "fill a void in what we feel is responsible dialogue about homosexuality in the way that we know how--science."

Camille Paglia, professor of humanities at the University of the Arts in Philadelphia and author of Sexual Personae, roused the audience with her opinions on the roles of homosexuals in society.

"We have to stop sermonizing, sanctimony...clubbishness and cliquishness," she said. Paglia said tension between homosexuals and heterosexuals ensures the survival of homophobia.

Homosexuals must allow for debate and discussion and stop propaganda against homophobia, Paglia said. "Scholars and scientists must think of themselves as being larger than their gay identity," she said.

Simon Levay, chair of California's Institute of Gay and Lesbian Studies said establishing a biological basis for homosexuality poses both positive and negative threats.

It is negative, he said, to risk calling homosexuality a disease. But he said evidence of a biological link is positive in that it helps to erase prejudice by those who believe that homosexuals are heterosexuals who have made some sort of incorrect choice.

Despite continual controversy surrounding the role of biological data, scientists continue to conduct extensive research in the field.

Dean H. Hamer, chief of a National Institutes of Health section on Gene Structure and Regulation, said there were three methods by which to study biological causes of a trait: analysis of trends in families, examination of "candidate" genes and linkage analysis.

Pedigree analysis, or studying whether traits run in a family, is commonly used to test whether or not a trait is genetic.

According to data presented by Dr. Richard C. Pillard, a Boston University professor of psychiatry, 4 percent of the brothers of heterosexual men are gay, while 22 percent of the brothers of homosexual men are gay. This data supports the hypothesis that homosexuality is at least in part genetic, Pillard said.

Other scientists presented other strategies by which to study biological differences between homosexuals and heterosexuals, involving the structure of a given part of the brain. Levay studied differences in the size of a certain part of the brain's hypothalamus which is thought to regulate sexual behavior.

Evan S. Balaban, assistant professor of biology, said there is precedent for physiological differences which correlate to differences in behavior. For example, Balaban said, patterns of singing in birds have been linked to structural differences in the brains of various animals, much as structural differences in humans may be linked to differences in sexual orientation