Sex fluidity in nature isn’t exceptional – it is actually quite common, actively challenging the male/female binary! And it manifests in a multitude of ways, much like the way we, humans, experience it.

Changing sex – several species of fish are sequential hermaphrodites, which means they are able to change their sex depending on various factors like age and social dynamics. Clownfish are a famous case, which are born exclusively male and live in communities led by a large dominant female. When she dies, the dominant male (the second-largest fish in the community) will change sex and take her place. The rest of the community consists of sexually immature males. On the contrary, most species of parrotfish are born female and later change sex in case the dominant male dies.

Parthenogenesis – asexual organisms reproduce without a mate, creating identical clones of themselves. This process exists amongst plants, fungi, and some animal species. As an example, the desert grassland whiptail lizard is an all-female species, which means their reproduction method doesn’t require male fertilisation. Some animals are also able to reproduce both sexually and asexually, such as many stick insects. In case of asexual reproduction, the female only produces daughters that are her identical clones.

Simultaneous hermaphroditism (female and male organs in the same individual) – up to 90% of flowering plants (e.g. tomatoes, apple trees, roses etc.) are simultaneous hermaphrodites, possessing both the stamen (male reproductive organ of a flower) and the pistil (female one). Additionally, some animals, such as most land snails, slugs, and earthworms, are capable of fertilising each other during the mating process. Self-fertilisation also becomes an option when a mate isn’t available, which benefits the survival rate.

Sex fluidity – in many cases, the sex of a reptile is determined by the temperature during a certain stage of incubation – a process called Temperature-Dependent Sex Determination (TSD). Even small shifts (such as 1°C to 2°C) can affect the outcome. In order to preserve biodiversity, mother reptiles choose nesting sites with temperature gradients.

Velvet horn deer

“Velvet horn” is used to describe intersex white-tailed deers. Biologically, these are males that never shed the velvet on their horns, and have the physical appearance typically associated with females. Their testicles never fully drop, therefore they lack typical testosterone levels seen in bucks. Velvet horns live apart from buck/doe communities, and have been seen successfully adopting and raising orphaned fawns.

Spotted hyenas

Female spotted hyenas possess a “pseudo-penis” (along with a “scrotum”), which they use for urinating, mounting males and other females for dominance, mating, and giving birth. This organ is, in fact, an enlarged clitoris, which forms as the result of increased testosterone exposure in the womb. The “scrotum” is the result of fused labia and is filled with fatty tissue, which makes it look similar to the male scrotum. 

Maned lionesses

Five lionesses in Botswana have grown a mane and were documented displaying male-like behaviours, such as scent-marking and roaring, as well as mounting other females. A likely explanation is the increased level of testosterone, which directly affects mane development in lions.

The mushroom with 20000+ sexes

The spitgill mushroom (also called Schizophyllum commune) has over 23000 distinct sexes, properly called mating types. Individuals of any sex are able to mate with more than 22000 other compatible types. A massive number of sexes prevents inbreeding and ensures a high survival rate.

Seahorse dads

During the mating process, the female transfers her eggs to the male’s pouch. The male then fertilises the eggs and seals the pouch, being the one to carry and give birth to the young. Males are able to carry over 100 babies at a time.

Recognising this diversity isn’t claiming that human identities are the same as those of other species. Instead, it reminds us that diversity is a rule, not an exception. The world around us is far more complex, flexible, and imaginative than simple binary perspectives suggest, providing us with a deeper understanding of the remarkable variety of life.