Princeton Professor's 'Sex Is a Spectrum' Book Ignites Debate on Biological Categories

Princeton University professor Agustín Fuentes, a distinguished biological anthropologist, has recently drawn public attention following the publication of his new book, "Sex Is a Spectrum: The Biological Limits of the Binary." The book's release has prompted discussion, with critics questioning the alignment of contemporary academic discourse with established scientific understanding.

Brandon Warmke, in a recent social media post, highlighted Fuentes's prominent academic standing, stating, "You might be tempted to defend academia by saying Fuentes is a joke, not a real biologist. But he is a full professor at Princeton, a member of the AAAS, and Princeton just published his book in its biology catalog, so I'm not sure academia really beats the allegations here." This tweet underscores a perceived tension between Fuentes's credentials and the controversial nature of his arguments regarding biological sex.

Fuentes's "Sex Is a Spectrum," published by Princeton University Press in 2025, argues that human biological sex is not a strict binary but rather exists along a continuum. He posits that traditional understandings of male and female, often based on singular biological traits like chromosomes or genitals, fail to encompass the full range of human biological variation. Fuentes has indicated that publishing such a book in the current United States climate is a "political act," expressing concerns about what he perceives as political degradation and a desire to regain Spanish citizenship.

This is not the first time Fuentes's work has sparked academic debate. In 2021, his article in Science, titled "“The Descent of Man,” 150 years on," critically assessed Charles Darwin's seminal work. Fuentes asserted that Darwin's views on race and sex were "problematic, prejudiced, and injurious," and controversially claimed Darwin offered "justification of empire and colonialism, and genocide, through ‘survival of the fittest.’" These interpretations were met with strong rebuttals from other scholars, who accused Fuentes of misrepresenting Darwin's intent and committing the naturalistic fallacy.

Throughout his career, Fuentes, a Professor of Anthropology at Princeton since 2020 and an elected member of the American Academy of Arts and Sciences, has focused on "myth-busting" concerning human nature. His earlier work, including the 2012 book "Race, Monogamy, and Other Lies They Told You: Busting Myths about Human Nature," similarly challenged conventional understandings of race, aggression, and sex, advocating for a more nuanced, biocultural perspective.

The ongoing discourse surrounding Fuentes's latest publication and his broader academic contributions highlights a persistent tension within academia regarding the interpretation of biological realities and their intersection with social and cultural constructs. Critics suggest that while promoting inclusivity, some academic narratives may risk distorting fundamental scientific principles, leading to questions about the objectivity of certain scholarly endorsements.