Evolution and Love



Since the publication of The Origin of Species and The Descent of Man by Charles Darwin, biologists have come a long way in their quest to understand human behaviour, building up on Darwin's original ideas and revising/perfecting it with new evidences and observations. Age old questions what is love?, where do human morality stem from etc are now understood reasonable well thanks to the research of sociobiologists and evolutionary psychologists,specially in the last two decades of 20th century. Their work points to an entire gamut of human emotions being rooted in our evolutionary history. Love, like all other human emotions is also rooted in the evolutionry history. It should be noted that evolutionary psychologists use the term love and sex interchangeably to mean the feeling of romantic attractions, courtship, mating and and the act of sex between opposite sexes. The term love and sex will be used interchangeably in this greater sense throughout this writeup. This writeup is by no means a scholarly or a scientific essay. Instead my aim is to quote some of the scientists and science authors (in books and TV shows) with my annotations to provoke the readers to read up on these fascinating issues further. No attempt is made to organize or structure it in any way. Needless to say the findings of Evolutionary Psychology (EVP) will sound shocking to many. But science is about truth, not about political correctness.That's how it has to be seen.

A slew of well written books and essays have been written by many experts in evolutionary psychology on this topic. The works of David Buss, Helen Fisher, Geoffrey Miller, Robin Baker and many others are worth mentioning. TV shows like the Science of Sex (TLC), Gender Wars (Desmond Morris) etc are also quite illuminating.

What is the root origin of love? The surprising but simple answer is the urge for the survival of genes. And what is the basis of the survial of the genes? To put it rhetorically, its the laws of Physics (stupid). We may not realize this origin when reading or listening to a beautiful love poem or song. To quote from "Mystery Dance: On the Evolution of Human Sexuality" by Margulis and Sagan('91):

All our desires, passions etc, reflect inanimate tendencies already implicit before life in the second law of Thermodynamics. Sexual reproducers, living beings making more of them - selves, achieve not only biological ends, but those of physics as well. p-46:

The survival of genes require the physical survial of an animal to reach reproductive to be able to choose a mate to pass off the gene to the offspring. It is the send step that lies at the origin of love, courtship of love to be precise. Darwin touched this aspect in the idea of sexual selection in the Descent of Man. But this idea find its fullest exposition in modern evolutionary psychology(EVP). Males and females choosing each other for specific attributes drove, through sexual selection the evolution of such human features as brain size increases, sexual organ characteristics and human behaviors in general. Many of modern courtship techniques have parallels in evolution, like the long tailbones of peacocks, which have grown large to attract peahens, since peahens in turn were attracted by long tails of peacocks. To quote Margulis and Sagan:

Technology, civilization cannot distance us from our animal selves, but instead accentuate them. Trendy glasses, epaulets etc are similar to tailbones of peacocks (p-170)

As revolting as it may sound, infidelity(cheating) in love, jealousy,rape etc are also rooted in evolution and evolutionary psychologists deal with these topics too in their research. In their book "The Natural History of Rape" Thornbull and Palmer explains the origin of rape as an evolutionary adaptive mechanism to maximize gene propagation. Quite predictably they evoked strong reactions form critics. But most of their critics committed the Is-Ought logical fallacy, believing that just because something has been classified as "natural," it must also have been implied as morally okay. But Thornbull and Palmer did not imply that. This linking of rape to evolutionary adaptation is cited on page 45 of the book "Sexing the brain" by neurobiologist Lesley Rogers quoting another biologist Matt Ridley:"Rape was evolutionarily adaptive"

Cheating in love is also evolutionarily rooted. Cheating is in our genes, narrates Ms. Kathleen Turner in The Science of Sex(TLC). So it must have evolutionary advantage in our past. With huge quantity of sperms in men, its to their evolutionary interest to father as many children as possible. With one egg per month women has less advantage in infidelity, yet it does exist, so must have some advantage. More resources for her child through the extra mate is the explanation for female infidelity. It provided genetic advantages to both males and females in evolutionary past (and still does today). This fact of evolution is also cited in Joann Ellison Rodgers' tome: "Sex: A Natural History" on page 215:

Deception appears to be necessary and therefore built into our sexual biology
Again not to confuse IS with OUGHT. What nature prescribes, nature also proscribes (via conflicting urges). It is this conflicting forces (or instincts) within humans that act as the stabilizing force in evolution.

Curiously, Evolutionary Biologists have found a correlation between degree of female infidelity with the quantity of sperm (testicle size) of the males of a species. Humans lie between the two extremes of Gorilla (least likely to cheat, small testes) and Chimpanzee (most likely to mate with multiple partners, largest testes).

This correlation has been cited in the TLC TV show as well as on page-339 of "Sex: A Natural History":

"Men's relatively large testes are a solid evidence that women in evolutionary history were promiscuous"

Another insight from EVP is that humans are not evolutionarily adapted for strict monogamy. As biologist Meredith Small points out on p-17 in her book "What's Love got to do with it" that women, as well as men, might not be biologically designed for monogamy citing that only 14% of the 200 species among primates are monogamous.

In her book "The Anatomy of Love" Helen Fisher writes:

"From a darwinian perspective, however, there were advantages to serial monogamy millenia ago". From a darwinian perspective, having children with more than one partners often make genetic sense" (p-159).

Polygamy is also roughly correlated with male to female body size ratio, which in case humans suggest a moderate polygamic tendency, as cited by Meredith Small (What's Love got to do with it) on page 20: Women are 80% of men physically,suggesting mild polygamy. Rodgers also mention this correlation on page-338 of her book.

All this shows that humans are at least not designed for strict monogamy or strict harem system either.

Jealousy also is evolutionary in origin. As David Buss points out in his book "The Dangerous Passion: Why Jealousy Is Necessary in Love and Sex" and also in the TLC show on Science of Sex that we are here because our ancestors were jealous. Those who were not did not leave any descendents. Needless to say that does not mean that TODAY EVERYONE has to be jealous. Apart from the fact that evolutionary traits are statistical, the evolutionary needs also change slowly over time as part of evolution.

An important element in sexual selection is body odor. Each of us have unique odor like fingerprint, which serves as fitness marker in evolutionary paradigm. Margulis and Sagan mentions that on pages 179-80. They also mention body odor as a sign of healthy immune systems. They cite an experiment of sniffing effect of sweaty male T- shirts by women. As the evolutionary root of that they mention that our mammalian ancestors were nocturnal, so had to depend on sniffing as primary mate selection means.

In the "Anatomy of Love", page-42, Helen Fisher writes:

Male essence(sweat) helps maintain regularity of female menstrual cycle. Hence females's (unconscious) attraction to male smell may be evolutionarily caused. The reason males now use deodorants and women prefer them may be culturally conditioned by the aggressive selling/ advertizing of producers and making perspiration is equaled to uncleanliness.
Joann Rodgers also mentions in her book on page-251 that women prefer men with the most dissimilar MHC genes (as observed through sniffing T-shirts soaked in armpit). Needless to say that these preferences are instinctually hardwired by evolution, not by conscious choice.

Scientists have identified the hormone that carries this distinct odor in men (generically called pheromones) called androsterone and the detectors for that odor in women called VNO (Vomeronasal organ). This confirms that humans also use sniffing (but in a much more subtle way) like animals to check out their mates instinctively via their VNO. It should be pointed out that the pheromone sniffing is not consciously done, the usual stinking male sweat is not due to the male pheromone in his sweat, but due to the bacterial degradation in his sweat that is exposed to the atmosphere for some time. That smell is conscious and made through the usual olfactory nerve, the instinctual smelling of pheronome in sweat is through VNO bypassing the olfactory nerve.

Why do women have cryptic estrus (Concealed ovulation)? The reason cited for that by Margulis and Sagan on p-197 of their book is that it helped male bonding with their women in the evolutionary past. The TLC series "The Science of Sex" narrated by actress Kathleen Turner also mentions that concealed ovulation helped pair bonding in our evolutionary past. Basically by hiding when she is infertile she forced the man to be always around her because he feared she would be mating with another man and sire child with him, and him having to take care of that child.

That the feeling of love is triggered by some features in males and females which is perceived as beauty or sexiness is obvious to anyone. But these markers are programmed by evolution as markers of some fitness. This is the finding of evolutionary psychologists. The work of Devandra Singh of UT Austin pointing to Waist to hip ratio as an evolutionary marker for healthy pregnancy is cited by Rodgers. Men are sexually attracted to low waist-to-hip ratios in females, and a low female waist-to-hip ratio really correlates with youth, fertility, and health. On page 148 of "Why We Feel? The Science of Emotions" Evol. Psychologist Victor Johnston mentions that a hip/waist ratio of 0.7 signifies an ideal androgen/estrogen ratio required for fertility in women. So is lip-fullness. So the perception of beauty and thus sexual attraction is directly correlated with female fertility. For men one fitness marker is facial symmetry, thus women tend to prefer men with facial symmetry. Reference to this can be found on p-49-58 in Lesley Rogers' "Sexing the brain" quoting Randy Thornhill's theory of beauty and symmetry vs. fertility. In this context fitness should be understood as genetic fitness,good genes in simple terms. Again just to remind these preferences are instinctual and thus women will not be consciously aware of this.

Artistic creativity like music and painting, aesthetic sense, humor,athletic ability, and intellectual activity has all been identified by some evolutionary psychologists as the product of sexual selection. In fact they attribute the relatively large size of human brain to sexual selection pressure. Costly organs (brain consumes a lot of heat) serve as fitness markers. The pioneering work in this are is by Geoffrey Miller who has written a highly readable book titled "The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature". He contends that women view these abilities as markers of genetic fitness in men and that women's brain has also evolved to be able to discriminate these abilities in men. According to him, since all those qualities do not give them an obvious survival benefit, they must have provided and continue to provide a reproductive advantage to have survived and thrived. "Romantic" behavior like the making of complex art couldn't have aided our ancestors find more food or avoid predators. Thus it might have helped to serve as a marker of fitness of primitive men to primitive women with whom they wanted to mate. Of course the the romantic behaviours in primitive time were also primitive, and has evolved to its modern form.

When it comes to love and sex mention must be made about the battle of the sexes and mate competition. Biologists have traced these to sperms. Robin Baker has done detailed study of how sperms compete with each other to fertilize eggs. That competition is a sort of miniature version of the competition among males for a mate. Matt Ridley in his book "Red Queen" traces the origin of the battle BETWEEN the sexes (and the resolution thereof) to the evolutionary battle between male and female gametes that led to sex differentiation in the first place.

I have glossed over these fascinating new horizons of evolutionary psychology, which has taken up the most daunting task of humans trying to understand humans. Why are we the way we are. It is a dynamic new area of research and is sure to unravel age old mysteries of human behaviour nothwithstanding the stiff resistance from the PC police.


- Aparthib (aparthib@yahoo.com), 12th February, 2007