True hermaphroditism, where a single organism has fully functional male and female reproductive systems, exists throughout the animal and plant kingdoms. In humans, the picture is more nuanced: no person has two complete, fully functional reproductive systems, but some people are born with both ovarian and testicular tissue, or with sex characteristics that don’t fit neatly into male or female categories. These conditions are real, well-documented, and more common than most people assume.
What “Hermaphrodite” Means in Biology
In biology, a hermaphrodite is an organism that produces both male and female sex cells. This is extremely common in the natural world. Roughly 90% of flowering plants have both male and female parts in a single flower, making them hermaphrodites by definition. Every rose, lily, and tomato plant qualifies.
In animals, hermaphroditism takes two main forms. Simultaneous hermaphrodites carry functioning male and female organs at the same time. Earthworms, many snails, and most flatworms fall into this category. These organisms have evolved this way independently across at least eight major animal groups, including segmented worms, mollusks, and roundworms. Sequential hermaphrodites switch sex during their lifetime. Clownfish start life as males, and the dominant individual in a group becomes female (male-to-female). Many species of wrasse do the opposite, starting female and becoming male. Some gobies living on coral heads can change sex in either direction, allowing any two individuals to form a breeding pair.
Why the Term Doesn’t Apply to Humans
While “hermaphrodite” is a standard term in botany and zoology, it has fallen out of use in human medicine. The older terminology was vague and, as medical literature has noted, “demeaning and sensationalistic, conjuring mythic images of monsters and freaks.” No human is born with two complete, independently functioning reproductive systems the way an earthworm or a snail is.
The medical field now uses “differences of sex development” (DSD), sometimes called “disorders of sex development,” to describe the range of conditions where chromosomal, gonadal, or anatomical sex characteristics don’t follow typical male or female patterns. These are congenital conditions, meaning people are born with them. A multidisciplinary approach involving endocrinology, urology, gynecology, psychiatry, and psychology guides care for people with DSD across their lifetimes.
Humans Born With Both Ovarian and Testicular Tissue
The condition closest to what people picture when they search “hermaphrodite” is ovotesticular DSD, where a person has both ovarian tissue (with follicles) and testicular tissue in their body. It occurs in roughly 1 in 100,000 births. In some cases, a single gonad contains both tissue types, called an ovotestis. In others, one side of the body has an ovary and the other has a testis.
The physical presentation varies enormously. About three-quarters of people with ovotesticular DSD are raised as males, though fewer than one in five have typically male external genitalia. Some develop breasts during puberty regardless of how they were raised. Others experience menstruation, or atypical genital anatomy, or no outward signs at all. In one published case, a man with ovotesticular DSD had a beard, an Adam’s apple, no breast development, married at 27, and fathered two children before the condition was discovered. He reported no daily difference between himself and other men and had considered himself male his entire life. When examined, his body contained ovaries with functioning follicles, a uterus with endometrial tissue, and seminal vesicles, all present simultaneously.
How Genetics Create These Variations
Sex development is usually guided by chromosomes: XX typically leads to female development and XY to male development. But the process isn’t as binary as a simple chromosome check suggests.
One key example: in about 80% of cases where someone with two X chromosomes develops male sex characteristics, the cause is a gene called SRY that normally sits on the Y chromosome. During sperm formation in the father, a random genetic exchange moves SRY onto an X chromosome. A child who inherits that modified X chromosome will develop testes and male features despite having no Y chromosome. This happens as a chance event and is almost never inherited.
In rarer scenarios, a father may carry SRY on both his X and Y chromosomes, meaning a child who inherits his X still gets the signal for male development. Other forms of DSD involve the body’s response to hormones rather than chromosomal differences, or mosaicism, where different cells in the same body carry different chromosome combinations.
Fertility in People With Dual Gonadal Tissue
Most people with ovotesticular DSD have reduced fertility, but it is not impossible. Spontaneous pregnancies have been documented since at least 1988. In a review of 283 cases, 10 women with ovotesticular DSD carried a combined 21 pregnancies to term. These women either had an ovotestis at the time of delivery or had previously had the testicular portion removed. Nearly all had XX chromosomes. On the male side, only one man in that entire series fathered a child naturally.
Assisted reproduction has expanded the possibilities. In one case, a man with ovotesticular DSD and no sperm in his ejaculate had sperm retrieved directly from testicular tissue, which was then used for conception. He went on to father two children using that method. Others with intact uterine structures may be able to carry pregnancies through in vitro fertilization.
How Common Are Intersex Traits
Ovotesticular DSD, the most dramatic form, is rare at 1 in 100,000. But intersex traits as a broader category are far more common. The umbrella includes conditions like atypical hormone responses, chromosomal variations such as XXY, and differences in genital or gonadal development. A nationally representative survey in Chile identified 2.77% of the adult population as intersex, though estimates vary depending on how strictly the term is defined. Narrower definitions that count only visibly atypical genitalia at birth yield much lower figures, while broader definitions that include any chromosomal or hormonal variation push the number higher.
The wide range in estimates reflects a genuine complexity: sex development involves chromosomes, genes, hormones, hormone receptors, and anatomy, and variation can occur at any of these levels. Some variations are obvious at birth, others appear at puberty, and some are never discovered without genetic testing or medical imaging.