Our updated letter to the three ecology/evolution societies who claimed that sex was a spectrum

As I wrote on February 13, three important societies representing evolutionary biology, ecology, and systematics issued a grossly misleading statement aimed at the government. (It is dated February 5, but I don’t think it’s yet been sent):

As I reported recently, the Presidents of three organismal-biology societies, the Society for the Study of Evolution (SSE), the American Society of Naturalists (ASN) and the Society of Systematic Biologists (SSB) sent a declaration addressed to President Trump and all the members of Congress. (declaration archived here)  Implicitly claiming that its sentiments were endorsed by the 3500 members of the societies, the declaration also declared that there is a scientific consensus on the definition of sex, and the consensus is that sex is not binary but rather some unspecified but multivariate combination of different traits, a definition that makes sex a continuum or spectrum—and in all species! The bolding below is Jerry’s:

Scientific consensus defines sex in humans as a biological construct that relies on a combination of chromosomes, hormonal balances, and the resulting expression of gonads, external genitalia and secondary sex characteristics. There is variation in all these biological attributes that make up sex. Accordingly, sex (and gendered expression) is not a binary trait. While some aspects of sex are bimodal, variation along the continuum of male to female is well documented in 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). Beyond the incorrect claim that science backs up a simple binary definition of sex, the lived experience of people clearly demonstrates that the genetic composition at conception does not define one’s identity. Rather, sex and gender result from the interplay of genetics and environment. Such diversity is a hallmark of biological species, including humans.

And as I write this today, I am still baffled how the different traits are supposed to be combined to determine one’s sex. I’d also like to ask the three societies exactly how many human sexes there are. As I’ve said before, I’m embarrassed to have been associated with the SSE since it’s now rejecting science in favor of currying favor with “progressive” ideology. It’s okay for societies to respond to situations that fall within their ambit, as this case does, but it’s not okay for them to purvey bogus science to buttress a political position.

Our original letter included 23 signers, most of whom are included in this second and final version of the letter.  The first letter never received a response (I find that rather rude), but we’re hoping for a response to this one.

The list of signers has now grown to 125, whose names are placed below the fold to keep this post shorter. If we’ve counted correctly, the signers come from nineteen countries. (We have omitted the names of five medical doctors and a nurse who also signed.) Every signer was willing to make their names public—a condition for signing the group letter. Others I know of have written privately to the Presidents of the Societies—and received a response, so the Societies clearly didn’t think they had to respond to our first letter.

The point of this letter is not to show that our view is a “consensus” (the Societies did not poll their members, either), but simply to affirm that a variety of people in biology or adjacent areas reject the Societies’ construal of sex as both a “construct” and a “spectrum”.  The letter below speaks for itself.

By the way, the driving force for writing the letter and collecting the signatures was Luana Maroja, Professor of Biology at Williams College, so kudos to her. And below this line is our letter, which was sent to the societies four minutes before this posting.

Dear presidents of the Tri-societies: ASN, SSB and SSE,

We, Tri-society members and/or biologists, are deeply disappointed by your recent letter “Letter to the US President and Congress on the Scientific Understanding of Sex and Gender” issued last Wednesday, Feb 5, 2025, in response to Trump’s executive order “Defending Women From Gender Ideology Extremism And Restoring Biological Truth To The Federal Government”.

While we agree that Trump’s executive orders are misleading, we disagree with your statements about the sex binary and its definition. In animals and plants, binary sex is universally defined by gamete type, even though sexes vary in how they are developmentally determined and phenotypically identified across taxa. Thus, your letter misrepresents the scientific understanding of many members of the Tri-societies.

You state that: “Scientific consensus defines sex in humans as a biological construct that relies on a combination of chromosomes, hormonal balances, and the resulting expression of gonads, external genitalia, and secondary sex characteristics.”

However, we do not see sex as a “construct” and we do not see other mentioned human-specific characteristics, such as “lived experiences” or “[phenotypic] variation along the continuum of male to female”, as having anything to do with the biological definition of sex. While we humans might be unique in having gender identities and certain types of sexual dimorphism, sex applies to us just as it applies to dragonflies, butterflies, or fish – there is no human exceptionalism.   Yes, there are developmental pathologies that cause sterility and there are variations in phenotypic traits related to sexual dimorphism. However, the existence of this variation does not make sex any less binary or more complex, because what defines sex is not a combination of chromosomes or hormonal balances or external genitalia and secondary sex characteristics. The universal biological definition of sex is gamete size.

If you and the signers of this letter do not agree on these points, then the Tri-societies were wrong to speak in our names and claim that there is a scientific consensus without even conducting a survey of society members to see if such a consensus exists. Distorting reality to comply with ideology and using a misleading claim of consensus to give a veneer of scientific authority to your statement does more harm than just misrepresenting our views: it also weakens public trust in science, which has declined rapidly in the last few years. Because of this, scientific societies should stay away from politics as much as possible, except for political issues that directly affect the mission of the society.

Respectfully,

NAMES OF 125 SIGNERS ARE BELOW THE FOLD

[Click “continue reading” to see the names.]

In alphabetical order:

Charleen Adams, Lead Statistical Geneticist, Beth Israel Deaconess Medical Center

Eli Vieira Araujo-Jnr, biologist and independent journalist, Brazil

John Avise, Emeritus Professor, Univ, of California, Irvine

Nick Bailey, Research Fellow in Bioinformatics

Daniel A. Barbash, Professor, Molecular Biology and Genetics, Cornell University

Alexander T. Baugh, Associate Professor, Department of Biology, Swarthmore College

David Bertioli, Distinguished Investigator and Professor, College of Agricultural and Environmental Sciences, University of Georgia, USA

Andreas Bikfalvi, Professor MD PhD, University of Bordeaux, France

Franco Biondi, Professor of Natural Resources and Environmental Science

Ranieri Bizzarri, Professor of Biochemistry, University of Pisa, Italy

William J. Boecklen, Professor, Department of Biology, New Mexico State University

Jacobus (Koos) Boomsma, Emeritus Professor, University of Copenhagen Department of Biology

Glenn Borchardt, Director, Progressive Science Institute

Gary Bowering, Member, Royal Society of New Zealand

Gordon M. Burghardt, Professor of Psychology and Ecology & Evolutionary Biology (Emeritus), University of Tennessee

Chris Campbell, Research Assistant Professor (retired)/ University at Buffalo

Joseph Ciccolini, Professor/University Hospital of Marseille France

Kendall Clements, Professor, School of Biological Sciences, University of Auckland

Mark Collard, Chair in Human Evolutionary Studies, Simon Fraser University

Michael Coon, Scientist/Biopharma (cell therapy)

Athel Cornish-Bowden, Directeur de Recherche Émérite au CNRS (retired)

Richard Cowling, Emeritus Professor of Botany, Nelson Mandela University

Jerry Coyne, Professor Emeritus, Ecology and Evolution, University of Chicago

David Curtis, Honorary Professor, Genetics Institute, University College London, UK

Richard Dawkins, Emeritus Professor, University of Oxford

Robert O. Deaner, Professor, Department of Psychology, Grand Valley State University; PhD Biological Anthropology & Anatomy, Duke University

Gilly Denham, SSE member, Williams College

Lynn Devenport, Professor Emeritus of Psychology, University of Oklahoma

Chet Dickson, Secondary Education (retired)

Paul Doerder, Professor Emeritus Cleveland State University

Gavin Douglas, Postdoctoral Researcher, North Carolina State University

Janet Roman Dreyer, Retired PhD Research Fellow Caltech

Joan Edwards, Samuel Fessenden Clarke Professor of Biology, Williams College

Nelson Jurandi Rosa Fagundes, Associate Professor, Department of Genetics, Federal University of Rio Grande do Sul

Lars Figenschou, PhD. The Arctic University of Norway

David Frayer, Prof. Emeritus – Anthropology, University of Kansas

Steven M. Fredman, Associate Professor of Physiology & Neuroscience (retired)

Jonathan Gallant, Professor Emeritus of Genome Sciences, University of Washington

Constantino Macías Garcia, Full-time researcher (professor), Instituto de Ecología, Universidad Nacional Autónoma de México (UNAM)

Brian Gill, retired natural history curator from Auckland Museum, New Zealand

David Greene, Professor, California State Polytechnic University, Humboldt

Christy Hammer, Associate Professor of Education, Sociology, and Women and Gender Studies, University of Southern Maine

Brian Hanley, Biologist, PhD. UC Davis

Sheila Rutledge Harding, Professor (ret’d), College of Medicine, University of Saskatchewan

Michael Hart, Professor, Simon Fraser University

Wesley Hawthornthwaite, BSc Neuroscience and Mental Health, Carleton University

James Heard, MS Biology, San Francisco State, SF, California, Retired

Jody Hey, Professor, Temple University

Emma Hilton, Developmental Biology, University of Manchester, U.K.

Susan Hoffman, Associate Professor of Biology, Miami University and 40 year member of SSE

Carole Kennedy Hooven, Senior Fellow, AEI; Affiliate, Harvard Psychology.

David Hughes, Teaching Fellow in Marine Biology (retired), Scottish Association for Marine Science

Peter M. Hurley, PHD Widlife Biologist, currently GIS Analyst, Grant County, NM

Christine Janis, Professor Emerita, Ecology, Evolution, and Organismal Biology, Brown University

Maria Garza Jinich, Retired CS professor. National University of Mexico.

Brian Jones, Retired Principal Fish Pathologist, Government of Western Australia

Robert King, Dr, University College Cork, Ireland

Anatoly Kolomeisky, Professor of Chemistry, Rice University

Shawn R. Kuchta, Professor, Biological Sciences, Ohio University

Michael Lattorff, Associate Professor (Parasitology) / University of KwaZulu-Natal, School of Life Sciences, Durban, South Africa

Benoît Leblanc, Lecturer, Sherbrooke University

Edward Lee, SSE member, Williams College

Harry Lusic, Associate Professor of Chemistry, William Peace University

Dan Lynch, Professor of Biology, Emeritus, Williams College

Maya Dyankova Markova, Associate Professor of Biology at the Medical University of Sofia, Bulgaria

Luana S. Maroja, Professor of Biology, Williams College

Edward Matalka, SSE member, Adjunct Professor of Biology, Worcester State University

Nicholas J. Matzke, Senior Lecturer, School of Biological Sciences, University of Auckland

Gregory C. Mayer, Professor of Biological Sciences, University of Wisconsin-Parkside

Stephanie Mayer, Senior Instructor Emerita, Department of Ecology and Evolutionary Biology, University of Colorado, Boulder

Marcella McClure, Microbiology retired from Montana State University

Richard J. McNally, Professor of Psychology, Harvard University

Axel Meyer, Lehrstuhl für Zoologie und Evolutionsbiologie, University of Konstanz

William Meyer, Educator, General Science, Mokena Junior High School, Illinois

Neil Millar, Biology textbook author and retired biology teacher

Michael Mills, Associate Professor of Psychology, Loyola Marymount University

Graeme Minto, Biologist, Πανεπεστιμιο Κριτις

Robert Montgomerie, Professor Emeritus of Biology Queen’s University

Greg Murray, Professor Emeritus of Biology, Hope College

Paulo Nadanovsky, Professor of Epidemiology, Universidade do Estado do Rio de Janeiro

Raymond Nelson, Biology Educator/North Thurston Public Schools

Howard S. Neufeld, Professor of Biology, Appalachian State University

Judith Totman Parrish, Professor and Dean Emerita/University of Idaho

Laurent Penet, PI in Agricultural Science, INRAe, Guadeloupe

Charles C. Peterson, Ph.D., Retired biologist Copper Mountain College

Steven Pinker, Johnstone Family Professor of Psychology, Harvard University

David Policansky, PhD, Scholar, US National Research Council, retired.

Chris Pook, Senior Research Fellow; Lead Technologist, The Liggins Institute, The University of Auckland

Anthony M. Poole, Professor, School of Biological Sciences, University of Auckland

Jorge Octavio Juarez Ramirez, PhD Candidate (Biological Sciences, Evolution and Genetics)/Universidad Nacional Autonoma de Mexico

Mary Rasmussen, Professor Emerita, Biomedical and Health Information Sciences, University of Illinois Chicago

Michel Raymond, Evolutionary Anthropology, Institute of Evolutionary Studies, Montpellier, France

Jaime Renart, Retired researcher, molecular and cellular biology, CSIC. Spain

Jacques Robert, Emeritus professor of cancer biology, University of Bordeaux, France

Mel Robertson, Professor Emeritus of Biology, Queen’s University at Kingston, ON, Canada

Rafael L. Rodriguez, Professor, Biological Sciences, University of Wisconsin-Milwaukee

James J. Roper, Professor (retired), ecology, evolution, ornithology, Institute for Tropical Ecology, Panama

Callum Ross, Professor of Organismal Biology and Anatomy, University of Chicago

Claudio Rubiliani, Docteur d’Etat. Honorary MCF Biologie des Organismes. Univ. Aix-Marseille (France)Visiting Professor Duke

Bjørn Ove Sætre, Developmental biology University of Bergen, Norway retired teacher

Lisa Sanders, Ph.D., Genetics, North Carolina State University

David Scadden, Professor, Stem Cell and Regenerative Biology and of Medicine, Harvard University

Julia Schaletzky, Professor of Molecular Therapeutics (Adj.), Dept. of Molecular and Cell Biology, University of California, Berkeley

Brandon Schmit, Wildlife Disease Biologist, USDA

Corrie Schoeman, Associate Professor, School of Life Sciences, University of KwaZulu Natal

Garvin Schulz, Dr., Department of Sociobiology/Anthropology, University of Göttingen

Elizabeth Sherman, Professor of Biology, Emerita, Bennington College

David Smith, Emeritus, Department of Biology, Williams College

Flavio S.J, de Souza, Group leader in Developmental Biology, IFIBYNE-CONICET, University of Buenos Aires, Argentina

Robert Paul Spence, Biotechnology company Chief Scientist

Steve Stewart-Williams, Professor of Psychology, University of Nottingham Malaysia

Malcolm Storey, PhD, naturalist retired

Mark Sturtevant, Associate Professor of Practice, Biological Sciences, Oakland University

John P. Sullivan, SSB member, PhD in Zoology, Duke University

Douglas Swartzendruber, Professor Emeritus, Biology, University of Colorado

Costas A. Thanos, Prof. Emer., Dept Biology, National and Kapodistrian University of Athens, Greece

Keith M. Vogelsang, Professor of Biology, Ivy Tech Community College

Schulte von Drach, Biologist (PhD). Journalist

Graham Wallis, Emeritus Professor, Population genetics and molecular evolution, University of Otago

Philip Ward, Professor Entomology, University of California Davis

Bob Warneke, Jr., BA (’73) and MS (’76) – Biology; Trinity University

Randy Wayne, Associate professor of plant biology, Cornell University

Marcelo Weksler, Professor, Museu Nacional, Universidade Federal do Rio de Janeiro, Brazil

Landon Whitby, Chemical Biologist, PhD, The Scripps Research Institute

Mike Zenanko, Director Emeritus, Jacksonville State University