Why does nature give us both faithful swans and polygamous chimpanzees? Why has human society invented so many forms of family — and none of them turned out to be universal? The answers are not found in moralising textbooks. They are encoded in our DNA, in anthropological archives, and in the mechanisms of evolution that are as old as life itself.
In the 1940s, the US Army ran into a costly problem: uniforms and equipment made to a single standard fit almost nobody properly. Helmets slipped, belts were too loose, boots caused blisters. The solution seemed obvious — measure more soldiers and find the average.
That is exactly what they did. Engineer Gilbert Daniels measured 4,063 servicemen across ten physical parameters and calculated the “average soldier”. He then checked how many real people fell within the norm on at least three of those ten measurements simultaneously. The answer was zero. Not a single person out of four thousand qualified as “average” even by the most minimal criteria.
The military had to quickly move to adjustable gear and expanded size ranges. Aircraft cockpits were redesigned for actual human variation, not a statistical ghost. It changed aviation permanently.
“The average person” is a statistical illusion. In reality, every one of us is an outlier by some measure.
This has a direct bearing on finding a partner. The templates of the “real man” or the “ideal mother” are the same kind of myth as the average soldier. Every person is unique in their hormonal profile, psychological makeup, reproductive characteristics, and their vision of what family should look like. Accepting that diversity is the first step toward looking for the right person for you — not the person who fits an abstract standard.
The common belief that men are naturally polygamous and women naturally monogamous is a neat but oversimplified story. Evolution does not produce standards. It produces strategies — and there are far more than two.
Among birds, around 90% of species are monogamous — but for many of them, monogamy is social rather than genetic. Ornithologists have long known that chicks in the same nest often have different fathers. Females mate with several males, but the “official” partner remains the one who helps feed the offspring. This is not infidelity in any human sense — it is a strategy: social stability combined with genetic diversity.
Females of many mammals — cats, dogs, sea lions — deliberately mate with several males within a single cycle. The result is a litter with multiple fathers. This is biological insurance: if one male’s genes prove less resistant to a particular pathogen, another male’s genes may do better. Evolution thinks in portfolios, not in monogamy.
Nature is neither monogamous nor polygamous. Nature is opportunistic. It uses whichever strategy works best in the conditions at hand.
Humans are no exception. Anthropological research shows that out of 1,231 societies recorded in the Murdock database, 84% permitted polygyny (one man, multiple wives), around 1% permitted polyandry (one woman, multiple husbands), and only about 15% were officially monogamous. This does not mean most people lived in multi-spouse arrangements — many societies permitted it while a minority practised it. But it does confirm that “one husband, one wife, forever” was never the only form of family among Homo sapiens.
In peasant Europe right up to the nineteenth century, premarital pregnancy in certain regions was not a scandal but a form of vetting. The logic was brutally pragmatic: in an agricultural household, children were the labour force. A bride who had already given birth and survived — at a time when maternal mortality was enormous — had demonstrated both fertility and physical endurance. Her child would soon become an extra pair of hands. This was a cold calculation, not cynicism; simply a different value system in which the survival of the family outweighed religious norms.
In Polynesia, so-called “punalua” marriages were practised — group unions in which several brothers shared a wife, or several sisters shared a husband. Anthropologists interpret this in various ways, but one function was evident: the distribution of resources and risks in the context of small, isolated island economies. A tiny community could not afford the luxury of the nuclear family — it survived collectively.
None of this is exotic curiosity. It is a reminder that the form of family has always been an adaptation to circumstances, not an immutable law of nature. The circumstances have changed. The adaptations have too.
Inside each of us, a quiet molecular war is under way. Scientists call it genomic imprinting — a phenomenon in which the same genes behave differently depending on whether they were inherited from the mother or the father.
Genes arriving from the father are evolutionarily “interested” in the foetus extracting as many resources as possible from the mother: growing large, drawing more nutrients through the placenta. Genes arriving from the mother, by contrast, “try” to preserve her resources — because next time she may conceive by a different man, and his genes would benefit from the first child not having exhausted her entirely. This is not a conscious conflict; it is evolutionary logic written into molecules.
The practical consequences are real. Imprinting disorders are linked to conditions such as Prader–Willi syndrome and Angelman syndrome — where a disruption in either the “paternal” or “maternal” copy of a gene produces a markedly different phenotype than expected. Pre-eclampsia during pregnancy is also partly explained by this conflict: the placenta, staking its “claim” to the mother’s resources, sometimes crosses a line.
Pregnancy is not only the cooperation of two genomes. It is also their negotiation — one that does not always reach agreement.
In 1995, Swiss biologist Claus Wedekind conducted an experiment that entered the textbooks as the “sweat T-shirt test”. Men wore cotton T-shirts for two days without using deodorant or fragrance. Women then smelled the shirts and rated whose scent they found most attractive.
The result was far from random. Women consistently preferred the scent of men whose Major Histocompatibility Complex (MHC) genes — the part of the immune system responsible for recognising “self” from “non-self” — differed most from their own. The greater the immune profile difference, the more appealing the scent.
The evolutionary logic is straightforward: children with diverse MHC profiles are more resistant to a broader range of pathogens. Nature embedded a “genetic compatibility detector” directly into the olfactory system — long before we learned to run DNA tests.
One important detail: in women taking oral contraceptives, preferences inverted — they began to favour men with MHC profiles similar to their own. Hormonal state literally altered immune “taste”. Some researchers suggest this may be one reason why some couples who relied on hormonal contraception for a long time report reduced mutual attraction after stopping it.
More precisely — it exists, but not in the way we imagine. When a woman holds a newborn, specific brain regions do activate, oxytocin is released, and neural bonds of attachment begin to form. This is real and measurable.
But the same thing happens in men who actively care for an infant. And in grandmothers. And in nannies. And in adoptive parents. Neuroscientist Ruth Feldman of the Hebrew University of Jerusalem showed that in fathers who were the primary caregivers of newborns — in couples where the mother worked — brain activity during contact with the child was virtually identical to that of mothers. Including the very regions commonly described as the seat of the “maternal instinct”.
The mechanism is not gendered — it is contact-based. Attachment forms through repeated physical closeness, shared rituals and emotional responsiveness. It is a skill, not a gift received at birth.
Caring for a child is not an instinct that switches on. It is a skill that develops — and it is available to anyone willing to practise it.
A stark historical illustration: the experiment attributed to Holy Roman Emperor Frederick II, recorded by the chronicler Salimbene de Adam in the thirteenth century. Frederick isolated newborns to discover which language they would speak “naturally”. Wet nurses were forbidden to speak to the infants, to hold them unnecessarily, to sing lullabies. The children did not speak. They died. The chronicler wrote: “They could not live without the petting and joyful faces and loving words of their foster mothers.”
Attachment is a biological need. But it is formed through practice, not through chromosomes.
Module 2 (Donor Selection & Genetics) includes practical tools for assessing genetic compatibility, including Extended Carrier Screening (ECS) and MHC compatibility data. Module 1 (Matching & Co-Parenting) helps you define which family model fits you before the first conversation. Both are available free in the Learn section.
an epigenetic mechanism in which a gene’s activity depends on whether it was inherited from the mother or the father.
a group of genes encoding immune recognition proteins. Greater MHC diversity between partners increases immune resilience in offspring.
a form of marriage in which one woman has multiple husbands simultaneously. Rare but documented in a number of traditional societies.
the situation in which having two different versions of the same gene confers greater fitness than having two identical versions.