We, the Council of the Society for the Study of Evolution, strongly oppose attempts by the Department of Health and Human Services (HHS) to claim that there is a biological basis to defining gender as a strictly binary trait (male/female) determined by genitalia at birth. Variation in biological sex and in gendered expression has been well documented in many species, including humans, through hundreds of scientific articles. Such variation is observed at both the genetic level and at the individual level (including hormone levels, secondary sexual characteristics, as well as genital morphology). Moreover, models predict that variation should exist within the categories that HHS proposes as "male" and “female”, indicating that sex should be more accurately viewed as a continuum.* Indeed, experiments in other organisms have confirmed that variation in traits associated with sex is more extensive than for many other traits. Beyond the false claim that science backs up a simple binary definition of sex or gender, the lived experience of people clearly demonstrates that the genitalia one is born with do not define one's identity. Diversity is a hallmark of biological species, including humans. As a Society, we welcome this diversity and commit to serving and protecting members regardless of their biological sex, gender identity or expression, or sexual orientation.
*Here we are speaking of the multi-dimensional aspects that underlie male-ness and female-ness, including hormones, physiology, morphology, development, and genetic aspects. We acknowledge that many of these aspects are bimodal. Furthermore, some of these aspects are discrete categories (e.g., XX/XY, SRY presence/absence, gamete size, sperm production vs egg production, presence/absence of certain genitalia), but these categories don’t always align within individuals, are not always binary, and should be irrelevant to the determination of a person’s legal rights and freedoms.
Continue reading for a copy of the letter sent to the Secretary of the Department of Health and Human Services.
Secretary Alex Azar
Department of Health and Human Services
Hubert H. Humphrey Building
200 Independence Avenue SW., Room 445-G
Washington, DC 2020
October 30, 2018
RE: Scientific Understanding of Sex and Gender
Dear Secretary Azar,
As scientists, we write to express our concerns about the attempt by the Department of Health and Human Services (HHS) to claim that there is a biological basis to defining gender as a strictly binary trait (male/female) determined by genitalia at birth.
Variation in biological sex and in gendered expression has been well documented in many species, including humans, through hundreds of scientific articles. Such variation is observed at both the genetic level and at the individual level (including hormone levels, secondary sexual characteristics, as well as genital morphology). Moreover, models predict that variation should exist within the categories that HHS proposes as "male" and “female”, indicating that sex should be more accurately viewed as a continuum. Indeed, experiments in other organisms have confirmed that variation in traits associated with sex is more extensive than for many other traits. Beyond the incorrect claim that science backs up a simple binary definition of sex or gender, the lived experience of people clearly demonstrates that the genitalia one is born with do not define one's identity.
Diversity is a hallmark of biological species, including humans. Our three scientific societies represent over 3000 scientists, many of whom are experts on the variability that is found in sexual expression throughout the plant and animal kingdoms. If you wish to speak to one of our experts or receive peer-reviewed papers that explain why there is a continuum of sexual expression, please contact us at president@evolutionsociety.org.
Sincerely,
Dr. Hopi Hoekstra
President, Society for the Study of Evolution
Professor, Harvard University
Dr. Sharon Strauss
President, American Society of Naturalists
Professor, University of California, Davis
Dr. Susana Magallón
President, Society of Systematic Biologists
Professor, Universidad Nacional Autónoma de México