Sex and gender in the animal kingdom

The word “sex” is usually associated with TV channels and web sites containing tricky content. However, in science, this term is a synonym for gender, male and female, but according to some new interpretations – gender is all those more or less expressed forms of gender ambiguity.  The emergence of gender is linked to the emergence of sexual reproduction, one of the most important moments in the evolution of the living world, and not without a reason: this process enabled gene recombination, and with that the genetic diversity in a species. Sexual reproduction allows for natural selection to occur and represents a strong evolutionary force. The oldest fossil proof of sexual reproduction comes from the Stenian era, a geological period 1.2 billion years ago, and is a specimen of a red algae species, called Bangiomorpha pubescens.

However, people have been fascinated by sexual dimorphism even in the ancient ages; the existence of the female and male sexes, which were obviously anatomically different and similar at the same time. That fascination lead the human imagination to create a being that holds the characteristics of both sexes – sexually integral, but a monstrous creature to the human race. In ancient Greek mythology, that was Hermaphroditus, the son of Hermes and Aphrodite, which was according to Ovid, in love with the water nymph Salmacis. The love of these two godly beings was so strong that they asked the gods to unite them eternally, which eventually happened and they became one being, with two sexes. According to another ancient source, Diodorus Siculus or Diodorus of Sicily, Hermaphroditus was born with the characteristics of both sexes.

Statue of Hermaphroditus, Museum of Fine Arts, Boston

And indeed, there are such creatures in the nature, having both male and female genitalia. Real hermaphroditism is frequent within invertebrate world - vineyard snail for example, in some jellyfish, but also with some vertebrae, more precise, in some fish species – the clownfish (Amphriprion). The latter ones have known to have a very interesting occurrence of sex change: these fish live in small flocks hiding around poisonous sea anemone, and a flock consists of one reproductive female, one reproductive male and a few non-reproductive males. In cases when the reproductive female dies, the reproductive male becomes a female and one of the non-reproductive males becomes a reproductive male. In other words, the animated movie “Finding Nemo” would be a very bizarre “X-rated” story if the screenwriters stuck to scientific fact. Not only would Nemo's father become his mother after the death of the female, but Nemo would become his father's reproductive partner. This variation on the topic of hermaphroditism, when a unit is born as males, and later in life transform to females is is called protandry and it has its' match in protogyny – when a unit is born as female and then changes to male. Simultaneous hermaphroditism, when a unit has male and female genitalia at the same time is restricted to the world of invertebrates, and besides the aforementioned vineyard snail, it's also characteristic for earthworms.

When we speak about humans, their sex and sexuality, modern biology doesn't support the idea of gender as pure sexual dichotomy. The development process of primary and secondary sexual characteristics has so many levels and any change in some of these phases can have dramatic consequences on the sexuality of the individual. We start life almost as hermaphrodites and only the combination of chromosomes during fertilization gives a hint of the future sex. The female sex cell holds only the X chromosome, and male sex cells can hold either X or Y. If an egg cell is fertilized by a sperm carrying the X chromosome, the XX combination determines the female sex, and if the egg cell is fertilized by a sperm carrying the Y chromosome, the XY combination determines the male sex. However, it is not all that simple. The concept of gender should be observed with care, taking into consideration all aspects of this issue. Embryology has shown that there are no significant differences in the early stages of the urinary-genital tract development. In the fifth week after fertilization, some things start to change and the beginnings of male or female sex glands (gonads) start to emerge from the same embryonic tissue. Somewhere around week 6, gonads are reprogrammed and become testicles or ovaries. If testicles are developed, they start producing sex hormones which cause the Fallopian tubes and the uterus to wither, and ductus deferens is developed. If ovaries are developed, then upon the production of estrogen ductus deferens withers. The same hormones that determine which parts will develop and which will wither, determine the development of external sex organs. However, not until puberty these organs start to direct the development of secondary sex marks – facial hair in men, breast development in women - and give the “sign” for the beginning of the final stage of sex organs development which then become functional.

In nature, transgender and intersex are not rare occurrences and they have many faces. External characteristics (phenotype) are always a product of interactions of the hereditary basis (genotype) and the environment, however, nowhere else in nature these changes and deviations from the typical sex are stigmatized as they are in humans. As we could see, transgender and inter-sexuality in some animal species are part of the evolution cycle of an unit, however, in human society, persons whose sex, gender and sexuality don't fit the ingrained definitions, suffer discrimination, stigmatization and violence. According to the Office of the UN High Commissioner for Human Rights definition, “intersex people are born with sex characteristics that do not fit typical binary notions of male or female bodies”. The term “hermaphroditism” was substituted with this new term “intersex”, but the overall term for all those phenotypes that don't fit the typical definitions of gender is “disorders of sex development” (DSD). This term is controversial because it's a fertile ground for stigmatization of intersex people since it describes their state as a “sickness”. Also, even though the term DSD was introduced in 2006, the community which it describes has never accepted this description of their state. According to a research published in March this year in the Journal of Pediatric Urology, the preferred terms are “intersex” and “variations in sexual development” and even one third of respondents said that they wouldn't visit a clinic whose name contained the term “disorders of sex development”. World Health Organization refers to DSD as “intersex characteristics or states”.

The unavoidable part of the LGBTI acronym is the community of people with different sexuality from those that are considered typical sexual behaviour. Homosexuality is often described as “unnatural” and is identified with pedophilia, and the advocates of this thesis argue how homosexuality can't be found in the animal world. However, science has documented cases of same sex intercourse in animals too. In fact, homosexual behaviours in animals is often a part of the overall sexual behaviours, which means that we're usually talking about bisexuality in these cases.

Mallard (Anas platyrhynchos), own work

Around 8% of rams, according to one research, shows more interest in the same sex if given a chance to choose, while one fourth of black swans pairs (Cygnus atratus) are same sex. Along with that, these swans sometimes organize in threes with one female and build a nest where the female lays eggs, just to be chased away and leave the eggs and eventually the young to two males to take care of them. Young that have been taken care like this have a bigger chance of survival, which is usually interpreted with the thesis that same sex couples are better in defending their young and territory. Mallards (Anas platyrhynchos) are known for same sex sexual activity in males (sometimes even around 19%), while it has been documented that in some seagull species, Larus occidentalis for example, up to 15% females shows homosexual behaviour. Among mammals, homosexual behaviour has been described in some dolphin species, giraffes, bonobo chimpanzees, macaque monkeys, dogs, sheep, buffalos, elephants and lions.

There are numerous variations of sex in nature, and we still don't understand how one unit develops its' gender and sexual identity and sexual orientation. It is clear that it's affected by a large number of genetic factors and environment factors, however humanity keeps repeating the same mistake throughout history: we are usually afraid of things that are different and which we don't understand, and that fear and wonder is easily masked in hatred. However, those things different are just a variation of ourselves, and confronting a cognition like that leaves no space for hatred. 

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