{"id":42900,"date":"2026-08-17T07:15:00","date_gmt":"2026-08-17T14:15:00","guid":{"rendered":"https:\/\/www.lifeandnews.com\/articles\/?p=42900"},"modified":"2026-10-27T00:03:14","modified_gmt":"2026-10-27T07:03:14","slug":"biological-sex-is-neither-binary-nor-a-spectrum-a-biologist-explains-how-its-multidimensional","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/biological-sex-is-neither-binary-nor-a-spectrum-a-biologist-explains-how-its-multidimensional\/","title":{"rendered":"Biological sex is neither binary nor a spectrum \u2013 a biologist explains how it\u2019s multidimensional"},"content":{"rendered":"\n

Ari Berkowitz<\/a>, University of Oklahoma<\/a><\/em><\/p>\n\n\n\n

Many people recognize that gender \u2013 how a person identifies, presents themselves and is perceived \u2013 has nuances<\/a>. Some people identify and present as women, others as men, and still others as nonbinary.<\/p>\n\n\n\n

But there is a common misconception<\/a> that biological sex \u2013 usually determined by a person\u2019s sex chromosomes, gonads (ovaries or testes) or genitals \u2013 is binary. This idea assumes that everyone is biologically either female or male, with no ambiguity or intermediacy.<\/p>\n\n\n\n

The assertion that sex is binary is essentially saying that people are what scientists call sexually dimorphic<\/a> \u2013 that is, the sex-related biological traits of females and males don\u2019t overlap. Illustrating this idea on a graph<\/a> of how many adult females and males<\/a> measure within a certain range for traits such as the amount of coarse hair on their body would look like two separate bell curves.<\/p>\n\n\n\n

But biologists and physicians have long known that sex-related biological traits are not sexually dimorphic. Instead, as I explore in my new book,\u201cThe Binary Delusion: How Biology Defies the Myth of Two Sexes<\/a>,\u201d there is overlap between females and males in each sex-related biological trait. Some people are more typically female in some traits, more typically male in other traits, and intermediate in still others.<\/p>\n\n\n\n

Intersex traits<\/h2>\n\n\n\n

Even primary sex traits<\/a> \u2013 sex chromosomes, gonads, internal reproductive ducts that transport eggs or sperm, and external genitals \u2013 are not always consistently female-typical or male-typical. Genitals can be intermediate<\/a> between typically female and typically male.<\/p>\n\n\n\n

All human embryos initially have identical reproductive tissues<\/a> that later develop into genitals. If an embryo has lots of the hormones called androgens, like testosterone, it will form a penis and scrotum; if an embryo has less of these hormones or has cells that don\u2019t respond to androgens<\/a>, it will form a clitoris and labia instead.<\/p>\n\n\n\n

With intermediate levels<\/a> of either androgens or androgen receptivity, an embryo will form a phallus \u2013 a penis or clitoris \u2013 of intermediate length, along with a structure intermediate between labia and a scrotum. One way of thinking about intermediate sex-related biological traits is by analogy of the color spectrum, with each person located somewhere along an axis that goes from red at one end to violet at the other.<\/p>\n\n\n\n

\"Color
A person\u2019s sex-related biological traits could be thought of as falling on a spectrum. Ari Berkowitz, CC BY-ND<\/a><\/figcaption><\/figure>\n\n\n\n

But primary sex characteristics other than genitals \u2013 such as sex chromosomes; gonads, or the ovaries and testes; hormones and hormone receptors; and internal reproductive ducts that transport eggs or sperm cells \u2013 can differ in their \u201cfemaleness\u201d or \u201cmaleness,\u201d making the color spectrum analogy misleading.<\/p>\n\n\n\n

For example, someone who has a Y chromosome but complete androgen insensitivity<\/a> \u2013 meaning their cells do not respond to androgens at all \u2013 develops testes hidden in their abdomen as well as typically female genitals. After puberty, they typically have a high-pitched voice, breasts and no coarse body hair. In appearance, most would consider them typically feminine<\/a>. This person cannot accurately be placed in one location on a sex spectrum because their sex-related biological traits differ in their femaleness or maleness.<\/p>\n\n\n\n

Multiple sliding scales are needed to represent this person\u2019s reality.<\/p>\n\n\n\n

\"Five
One person\u2019s sex-related biological traits may each fall on different locations on a sliding scale of variation. Ari Berkowitz, CC BY-ND<\/a><\/figcaption><\/figure>\n\n\n\n

Collectively, intersex variations occur in 0.2% to 6% of the population<\/a>, depending on which variations you choose to count.<\/p>\n\n\n\n

No consistent definition of human biological sex<\/h2>\n\n\n\n

Biologists usually define the sex of any animal<\/a> based on whether it produces small sex cells (sperm) or large sex cells (eggs), which are produced by testes or ovaries, respectively. But physicians assign a person\u2019s sex at birth<\/a> based on genitals, which may or may not match their gonadal sex (ovaries or testes).<\/p>\n\n\n\n

Someone can have male-typical gonads while having female-typical genitals, or the reverse. In fact, because the sex chromosomes, gonads and genitals in a given person can point in different directions with respect to their maleness or femaleness, it\u2019s not clear whether one of these alone<\/a> should determine someone\u2019s sex category. <\/p>\n\n\n\n

Society hasn\u2019t reached general agreement or consistency in how to define human biological sex. For example, regulators of elite women\u2019s athletics such as the International Olympic Committee<\/a> have repeatedly changed their sex tests<\/a> for women\u2019s competitions<\/a> over the past century<\/a>, going from genitals to sex chromosomes to testosterone levels. In March 2026, the IOC returned to using sex chromosomes<\/a>.<\/p>\n\n\n\n

However, having a Y chromosome does not by itself create a typically masculine body or provide athletic advantages. Most athletic advantages that males typically have are due to higher androgens at puberty, but for people whose cells respond less or not at all to these hormones, they may have little or no athletic advantage<\/a>.<\/p>\n\n\n\n

Overlap in secondary sex characteristics<\/h2>\n\n\n\n

There is also overlap between groups of adults categorized as female or male \u2013 based on either their chromosomes, gonads or genitals \u2013 in secondary sex characteristics<\/a> that develop at puberty. These include growth of breasts and coarse body hair, widening of hips and shoulders, and lowering of voice pitch.<\/p>\n\n\n\n

For example, females have larger breasts than males on average, but some males have larger breasts than some females<\/a>. Similarly, males have more coarse body hair than females on average, but some females have more coarse body hair than some males<\/a>.<\/p>\n\n\n\n

The amount of overlap differs for each sex-related biological trait. There is little overlap after puberty for voice pitch<\/a>, intermediate overlap for waist-to-hip ratio<\/a> and muscular strength<\/a>, and almost complete overlap for the sizes of nearly all<\/a> brain regions<\/a>.<\/p>\n\n\n\n

\"Four
Different biological traits have differing degrees of overlap between females and males. Ari Berkowitz, CC BY-ND<\/a><\/figcaption><\/figure>\n\n\n\n

Many people are more typically female in some biological traits, more typically male in others, and intermediate in still others. In such cases, people can\u2019t be placed accurately at one location along a single biological sex spectrum because there are multiple traits that can vary<\/a>, and an individual\u2019s biological measurements can land in different locations<\/a> along these different axes.<\/p>\n\n\n\n

In other words, biological sex is multidimensional.<\/p>\n\n\n\n

Human bodies are mosaics<\/h2>\n\n\n\n

One way of thinking about the multidimensionality of sex-related biological traits is as a mosaic. Neuroscientist Daphna Joel<\/a> and her colleagues developed this metaphor<\/a> to describe how people have brain regions and personality traits<\/a> that may be relatively female-typical in some, more male-typical in others, and intermediate in still others.<\/p>\n\n\n\n

I argue that across the body, each person has a unique combination of sex-related biological traits<\/a>, which can be thought of as a mosaic. For example, you might have female-typical height and coarse body hair, male-typical voice pitch, and intermediate muscle strength and facial structure.<\/p>\n\n\n\n

\"Graphic
A person\u2019s biological sex can be thought of as a mosaic, with some traits that are more typically female, some more typically male, and others more in between. Ari Berkowitz, CC BY-ND<\/a><\/figcaption><\/figure>\n\n\n\n

The fact that people are multidimensional in their sex-related biological traits means that the binary view of sex is fundamentally misleading. Biological sex has variations and nuances, just as gender does.<\/p>\n\n\n\n

Ari Berkowitz<\/a>, Professor of Biological Sciences; Director of the Cellular and Behavioral Neurobiology Graduate Program, University of Oklahoma<\/a><\/em><\/p>\n\n\n\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Ari Berkowitz, University of Oklahoma Many people recognize that gender \u2013 how a person identifies, presents themselves and is perceived \u2013 has nuances. Some people identify and present as women, others as men, and still others as nonbinary. But there is a common misconception that biological sex \u2013 usually determined by a person\u2019s sex chromosomes, […]<\/p>\n","protected":false},"author":56,"featured_media":42901,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[10,36,3410,38],"tags":[14850,312,365,11273,8807,16829,13076,885,891,886,860,9520,17954,162],"_links":{"self":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/42900"}],"collection":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/users\/56"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/comments?post=42900"}],"version-history":[{"count":1,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/42900\/revisions"}],"predecessor-version":[{"id":42902,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/42900\/revisions\/42902"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media\/42901"}],"wp:attachment":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media?parent=42900"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/categories?post=42900"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/tags?post=42900"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}