A Human Sexual Evolution Theory That Explains
Homosexuality, Heterosexuality & Bisexuality
The theory of human sexual evolution appearing on this website was first published in two installments in the Journal of the Gay and Lesbian Medical Association in 2000 (True Nature – A Theory Of Human Sexual Evolution, C. Gomes, JGLMA Vol.4, No.1 and JGLMA Vol.4, No.2).
‘True Nature’ presents arguments from various fields of study to show that the sexuality of human beings evolved over the course of millions of years, alongside and as a direct consequence of, increases in intelligence. Far from it being static over millennia and largely aligned with heterosexuality, a review of human sexual history spanning the globe – providing the ultimate litmus test of humanity’s true sexual nature - reveals the incredible plasticity of our sexual behavior, and humanity’s predilection for homosexuality.
This ever-present homosexual bias in humans remained unsuspected till now because the ubiquity of heterosexuality always presented an overarching prejudice when interpreting human sexual history, and also because a theoretical framework capable of making sense of its perplexing and contradictory nature was lacking.
Conclusions Regarding Human Sexuality
1. We are unique in the animal world in not possessing a sexual instinct that would compel us to engage
in heterosexual intercourse.
What indications are there that this is true?
- Humans are the only animal species that can choose not to have offspring. All other sexually reproducing animals are compelled to engage in heterosexual intercourse and reproduce when they sense the right combination of seasonal, pheromonal, and/or visual cues. This proves that humans do not rely on environmental cues, neither pheromonal nor visual, to dictate their sexual behavior.
- Humans are the only species where exclusive homosexual subgroups exist. In all other animal species where homosexual activity is seen, the same individuals invariably also engage in heterosexual intercourse because their sexual behavior is underpinned by a reproductive instinct.
2. It was the tremendous rise in intelligence in the course of human evolution that made the loss of our
sexual instinct possible.
Why was a sufficiently high intelligence level necessary?
- For our species to continue surviving, the human line could not lose its sexual instinct until it was possible for reproduction to be relatively assured without it. And this was only possible after humans had first found a benefit in producing offspring (realizing that children could provide care and protection in old age), and then discovered what caused reproduction (linking heterosexual intercourse to it). The tremendous insight required for both discoveries was only made possible by a sufficiently high intelligence level.
3. Humans discovered the role of heterosexual intercourse in reproduction not by scrutinizing their own sexual
behavior, but by making that correlation on another species first. The reason this was necessary is that instincts
are not tied to memory, and hence leave no memory trace of their operation with which to correlate a future event.
Crucially then, the domestication of dogs may have provided the first opportunity to closely observe the sexual
behavior of another animal species, and eventually make the breakthrough correlation. (See Link Between Dog
Domestication, Human Intelligence, And Neanderthal Extinction )
4. Once the mystery of reproduction had been solved, the road was paved for a short-lived nasal plug during fetal
development to eliminate the sexual instinct in the human line. It did so by isolating the developing vomeronasal
organ (VN0)- critical for pheromone detection and response - from chemical 'set-up' signals that would have likely
emanated from the concurrently differentiating sex organs, thus inhibiting the VNO's proper development and
functionality. This developmental change appeared within the last 200,0000 years. Of all hominin species that ever
existed, only homo sapiens gained knowledge of the essential role of heterosexual intercourse in reproduction.
Hence, all other hominin species necessarily continued to possess a sexual instinct (viz. a functional VNO),
irrespective of their brain size. (For a more in-depth explanation read a blog entry on the fetal nasal plug.)
5. The loss of the sexual instinct conferred upon homo sapiens a vastly increased intelligence level, and allowed them
to outthink, out innovate, and out compete the Neanderthals into extinction.
How did losing the sexual instinct accomplish this?
- Brains require neurons to tell them what to do, and this requires neurons to get activated and send a nervous impulse to other neurons.
- A neuron never works alone, but instead forms a temporary working group with other neurons that all fire synchronously (viz. together) to produce a combined neural signal whose strength is the summed strength of all neurons comprising the group.
- At any instant, there are many such independent neural groups. Each of these temporary groups of activated neurons represents one different thing that the brain could do in the next instant to time, ie. have a particular thought, observe something, initiate a movement, focus visual attention at some object, etc.
- The group of neurons with the greatest neural strength of operation wins out over all the other neural groups with lesser neural strength of operation, in so doing is able to dictate what the brain commands next, and occupies the seat of consciousness for the instant that it operates.
- Another neural-group battle begins anew in the next instant of time between different groups of neurons, all vying for control of consciousness. The content of the succession of dominant neural groups defines what we perceive as the stream of consciousness.
- Intelligence is simply any experience-based response, and is categorically different from instincts, which are inborn responses to environmental stimuli.
- Experience-based responses (viz. intelligence) and instincts vie for control of consciousness because both require large scale control of movement, and therefore can't work properly simultaneously because each may be trying to tell the brain to respond to the environment in ways that require conflicting movement responses.
- In nature, operation of instincts have such essential life-supporting and species-survival roles, that nature ensures that they must generally be able to displace from the seat of consciousness any prescription for behavioral response stemming from experience. To be able to do so, the number of experience-linked neurons that can form a single group, and their combined strength, must be less than that corresponding to instincts.
- Increased intelligence however, requires more and more input from past experience, and this requires more and more neurons becoming simultaneously involved in conscious decision making - which is to say, larger neural groups. However, given than instincts are characterized by neural groups that are relatively fixed in size - and do not grow proportionately with increases in brain size - they therefore constrain intelligence level in all animals possessing them.
- The loss of the sexual instinct in homo sapiens eliminated the constraint on the number of neurons allowed to form a single group, thus permitting greater use of prior experience in decision making, and giving rise to unprecedented powers of observation, deduction, intuition, invention, and abstraction.
- This allowed homo sapiens to start on the road to maximizing the potential intelligence derivable from the existing size of their brain, allowing huge increases in intelligence without significantly increasing brain size. This is evidenced by the comparable brain sizes of Neanderthals and homo sapiens, yet the quantum leap in technology, art, and culture made by human beings.
6. The loss of the sexual instinct and the resulting full conscious control of reproduction was highly
advantageous to humans.
- It facilitated monogamy within a multi-family group setting because individuals were no longer compulsively drawn to mate with other individuals of the opposite sex emitting sexual pheromones, thus reducing sexual tension and permitting increased social cohesion.
- It allowed births to be planned and timed appropriately with the availability of food and shelter resources as humans forged their way into new environments during various periods of global expansion, thereby reducing the mortality of infants and expectant mothers.
- It allowed competing groups of human beings to increase their populations in response to ongoing conflict and competition.
7. Lacking a sexual instinct, human sexuality is completely determined by individual experience.
What are the implications of this?
- Heterosexuality is not genetic in human beings. No genes have ever been found as a cause for heterosexuality. Heterosexuality is learned.
- Homosexuality is not genetic in human beings. No genes have ever been found as a cause for homosexuality. Homosexuality is learned.
8. A universal set of childhood sexual exploration behaviors exists that most strongly biases a homosexual
orientation development, over a heterosexual one, or a bisexual one. Therefore, though not inborn,
homosexuality is natural in humans, heterosexuality is not.
What gives rise to these childhood sexual exploration behaviors?
- All children have a natural tendency to sexually explore and stimulate their bodies from infancy, primarily the sensitive genital area, in attempts to derive tactile and olfactory pleasure from it. This pleasurable behavior has a much stronger potential to create same-sex attraction than opposite-sex attraction - if societal deterrents and/or a sufficiently strong heterosexual conditioning environment are absent. Male circumcision was invented to deter a homosexual orientation development by reducing the penis's production of smegma, and its sensitivity to tactile stimulation.
What indication is there that homosexuality is indeed natural in human beings?
- If we review the history of human sexuality we see that throughout recorded history in diverse cultures spread across the globe whenever homosexual behavior has been embraced and permitted, it has been so widespread and dominant that every such culture found it necessary to condemn exclusive homosexuality in order to ensure that a sufficient level of heterosexual activity existed to enable its survival. If heterosexuality was indeed an innate, largely universal characteristic of human beings, this historical regulation of homosexuality and enforcement of heterosexuality would not have been necessary.
populations - universally encourage heterosexuality while discouraging, or forbidding, homosexuality.
All material copyright 1991-2010 / Christopher Gomes