New Hypothesis: Dog Domestication Linked To Loss Of Human Sexual Instinct And Neanderthal Extinction


The kinship and partnership between human kind and dog has existed for many thousands of years. We have benefitted from that relationship in a multitude of ways, some clearly utilitarian – such as when dogs have served the role of guards, herders, hunting aids, and sled pullers – but of equal value, dogs have been our beloved companions, who through their unbounded love, affection, loyalty, and sometimes uncanny perceptiveness, allow us to connect to deeper emotional layers of ourselves, to nurture the esteemed human qualities of kindness and love, and to allay the stresses of daily life in ways human relationships often fail to do. Despite this acknowledged indebtedness to ‘man’s best friend’, I hereby propose that the most important role dogs played and one which changed the fate of the planet, has been lost in the margins of time – as the sole enabler for the emergence of modern man, Homo Sapiens. This relationship was directly responsible for the ascendancy of human beings, and the demise of the Neanderthals. Had dogs never been domesticated, our species’ would not have its defining highly honed intelligence level, and we would likely still be sharing the planet with Neanderthals.

Anyone familiar with the study of human evolution will know that the swift disappearance of Neanderthals from all areas where modern humans moved into, is one of the long standing mysteries in anthropology. Neanderthals were a highly successful hominin species that thrived right across Europe, southwest Asia, and Siberia for around 300,0000 years before modern humans arrived. Their survival amidst some of the most challenging climatic conditions during the last global glaciation attests to their resourcefulness. Yet, within the span of a few thousand years humans completely obliterated Neanderthal populations everywhere, presumably by outcompeting them. We were plainly smarter, it appears: we had more-refined tools, larger social and cultural networks, we developed an aesthetic sensibility as revealed by the first wall murals, figurines, and musical instruments ever created, we moved into areas of the globe Neanderthals had not succeeded venturing into, and most telling, we acquired a chin – not possessed by any other hominin species – which serves as a point of muscular attachment facilitating minute movements of the lips associated with speech ( Neanderthals it seems, never had the ability to communicate anything so complex as to require a highly developed language, a further sign of their lower relative intelligence level. These differentiating attributes of intelligence are all the more perplexing when one considers that Neanderthals had brains that were as voluminous as ours, on average. How can one explain this parity is brain size, but disparity in intellect, between Neanderthals and humans? I believe the answer lies in examining the relationship between instinct and intelligence.

There is a most fundamental connection between instinct and intelligence at a neural level that has previously not been suspected, but which has tremendous explanatory power. It reveals that instincts place a constraint on intelligence level in all organisms, and furthermore, losing instincts allows brains to achieve their full potential intelligence level. The salient points of the argument (found at can be summarized as follows:

  • 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, for example, 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 and problem solving- 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 instincts would therefore eliminate this constraint on the number of neurons allowed to form a single group, thus permitting greater use of prior experience in decision making – the prerequisite for increased intelligence.

Based on this neural model, it is clear that the key to higher human intelligence was losing the sexual instinct. My hypothesis is that of all hominins that ever existed, only Homo Sapiens – our species – was ever able to lose the sexual instinct. Losing the sexual instinct 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. Neanderthals conversely, must never have lost their sexual instinct, and this would account for their lesser intelligence. There are those who would argue however, that humans still possess a sexual instinct. Theirs is an untenable position – the most definitive indication that humans do not possess a sexual instinct is the freedom every one of us has to choose NOT to reproduce – a reproductive freedom that has no parallel anywhere else in the animal world! Instincts most characteristically, are compulsive in nature so this universal reproductive freedom is all the proof one needs that human beings uniquely lack a sexual instinct.

Why is it that it was only our species, Homo Sapiens, that managed to lose its sexual instinct, and not a single other hominin species that ever existed? The answer lies in the formidable barriers to losing it, which entailed first discovering a benefit to producing children, and then discovering what caused reproduction. Only then would reproduction be relatively assured without a sexual instinct, and a species still be able to survive. One of the barriers to losing the sexual instinct must have fallen at least a few hundred thousand years ago. In the course of hominin evolution there was a progressive increase in intelligence. At some stage, hominins would have acquired enough intelligence to understand the concept of aging and death. And with this knowledge came the realization that the prospect of survival in old age without the assistance of younger individuals was bleak. This was motivation enough to value having children. Neanderthals three to four hundred thousand years ago show some evidence of having cared for the elderly, implying that perhaps they already understood the predictive nature of aging, and formed social units in which prolonged parental investment in offspring was geared toward insuring care and protection in old age. But what of the other barrier – the knowledge of reproduction?

The knowledge of reproduction is so fundamental to human existence that it is easy to believe we have always possessed it. But like all knowledge, it had to be acquired at some point. How, and when, did we learn the role of heterosexual intercourse in reproduction? And furthermore, did other hominins also acquire this knowledge? Though there has been scant speculation about these matters, the unstated assumption is that hominins must have already understood reproduction by as early as perhaps a million or more years ago. This view does indeed appear reasonable when one considers that hominins were already displaying considerable skill in building stone tools by that point in time, an ability that requires forward planning, design conceptualization, selection of appropriate materials, and fine motor skill control to create the desired form from stone. Additionally, hominin species had also demonstrated remarkable adeptness at meeting new environmental challenges after spreading widely over the African continent, and then crossing into Eurasia about 1.8 million years ago. Surely, a mind capable of such feats would have likewise been able to deduce what made reproduction possible, wouldn’t it? I believe a compelling argument can be made to answer this question in the negative.

The reason is that instincts are triggered to operate solely by environmental stimuli, without the need, or capacity, to reference past experience. Hence, there’s a disconnect between instinct and long term working memory, and this presumably exists to prevent past experience from adversely affecting the operation of instincts. But in order to figure out the role of heterosexual intercourse in reproduction we require to correlate 2 events that are significantly separated in time: the incidence of heterosexual intercourse, and the resulting pregnancy. It was therefore an impossible task for any hominin species possessing a sexual instinct – irrespective of brain size – to have solved the mystery of reproduction by scrutinizing its own sexual behaviour. They had to deduce the role of heterosexual intercourse in reproduction by making the necessary observations on another animal species first. These prolonged observations on another animal’s sexual behaviour were only likely to have been made with the first steps toward animal domestication. Accordingly, we have to focus attention to the dog, the first animal to be domesticated.

The places and dates of wolf domestication are much debated. What is certain however, is that all the archaeological evidence indicates only humans domesticated dogs. Studies comparing the haplotypes ( a combination of alleles (for different genes) that are located closely together on the same chromosome and that tend to be inherited together) of dogs with that of wolves from different parts of the world, show that dog domestication may have begun as early as 135,000 years ago. The domestication process however, may have had multiple starts that lacked continuity even before this date, so we may be justified in speculating an upper limit for the advent of wolf domestication to be in the range of 200,000 years ago.

It is likely that humanity’s first steps toward that domestication process had its roots in Africa, probably in Ethiopia -the cradle of mankind – where the Ethiopian wolf is found in mountainous regions there. In fact, the basenji dog – the only canid in Africa that lives in the rainforest of central and western Africa – has an annual estrus timing that closely matches that of the Ethiopian wolf. Curiously, feral or domestic dogs in south Asia living in the tropic forest also match the Basenji’s annual cycle ( ). This may be of significance because the colonization of the world outside of Africa did trace a southerly path through Asia, and humans would have likely carried their dogs with them. A plausible scenario that would have allowed humans to infer the role of heterosexual intercourse in reproduction is one in which a female wolf pup was stolen, or adopted as a rescue. The importance of a female – and not a male – in this scenario is that a female wolf would have attracted wild male wolves when she was in heat, and matings would have at times perhaps occured at a safe but observable distance, enabling her observant human masters over time to eventually make a connection between these sexual encounters and any ensuing pregnancies. Years in which male wolves were not present to mate with the female wolf, would have conspicuously stood out as years in which the female did not become pregnant. After innumerable such observations the deduction regarding reproduction would have eventually become inevitable. This I propose, was the single greatest piece of deduction in the history of mankind, one that would unleash the full power of human intellect and bring the earth and all its creatures under our dominion!

What was it about our species that made us adopt a different attitude toward wolves, a species that must have long been regarded as a competitor? Why had Neanderthals never been inclined to do so? We’ll never know for sure, but we can conjecture. We see differences in culture presently between 2 closely related chimpanzee species – the bonobo and the common chimpanzee. Bonobos show less aggression toward each other than the common chimpanzee, and resolve disputes with sex and hugs/kisses. Similarly, there may have been a difference culturally between Homo Sapiens and Neanderthals – one that caused Homo to have empathy in certain situations, like when coming across an orphaned wolf pup, or throwing scraps of food at a wolf that stayed begging. Neanderthals conversely, may have always killed wolf pups on sight, or shooed away any lingering wolf, because they saw them as rivals. It is also likely that from the start our species was just a little more intelligent, even while still possessing a sexual instinct, because we were the newest branch of the family tree – and Africa’s Rift Valley had for millions of years consistently thrown up better and better versions of hominins leading eventually to us. Perhaps this latest increase in intelligence gave Homo an increased self confidence and prowess in all areas, including hunting, and it did not see the wolf any longer as a formidable competitor. Whatever the true story of wolf domestication, it had a most profound effect on our species’ intelligence, and it eventually spelled doom for the Neanderthals.

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