© David Staume 2007

Evolution is more than just a physical process

I want to tell you the story of the evolution of intimacy, a story that you would not have heard before. But before I do, there’s a prevailing view of evolution that I’d like to correct: the notion that evolution is a predominantly physical process.

When we hear the phrase ‘evolutionary trend’ we tend to think of the development of physical adaptations such as a primate’s opposable thumb, or a cactus’ spiny exterior, but evolution involves much more than an organism’s structure. Evolution favours whatever ‘works’, whether it’s a physical structure such as a better-shaped beak, a social structure such as the division of labour in an ant colony, or an emotional bonding that leads to more effective protection of offspring. The widespread view of evolution as a predominantly physical process only gives half the picture; evolution is just as capable of developing emotional and intellectual capacity as it is of developing hard-shelled eggs or mammary glands.

The evolution of intimacy involves the development of emotional capacity as well as physical capacity. Its story runs parallel to the evolution of sexual reproduction, which is its driving force, and it goes something like this:

Because we live in a world with no exceptions to the rule: you’re born, you live, and you die, species must reproduce to continue to exist. The most efficient forms of reproduction involve either splitting yourself in two to form two new organisms (the bacterial model), or having an all-female population where everyone is capable of giving birth and eggs don’t require fertilization (the reef-fish model). But despite the efficiency of these non-sexual reproductive models they are quite rare. The vast majority of species reproduce sexually; and they do so despite the fact that splitting your population into males and females and then bringing them together to combine their genes is a relatively wasteful and time-consuming process.

So why do the vast majority of species reproduce sexually? What could possibly trump the enormous efficiency of non-sexual reproduction?

In non-sexual reproduction every new individual is a facsimile of its parent, so species change can only occur through genetic mutation, which is a slow and haphazard process. Sex, on the other hand, shuffles the genetic material, and ensures that every offspring is different from its parents. This variability increases a species’ chances of survival in a changing environment. Sex trumps short-term efficiency with the significant advantage of long-term survival.

Because sex benefits long-term survival, evolution will tend to develop the capacities that lead to successful sexual reproduction. These include the skills of cooperation, communication, and coordination, all of which are required to locate a mate or meet up at a particular time; discern the gender, mood, and sexual availability of another individual; and successfully consummate the sexual act.

The diversity of these skills in the animal kingdom is extraordinary: Artic terns fly the circumference of the world to get together to mate. Penguins have stone-giving rituals to tell the genders apart. Fireflies have developed sexual signalling by light; guppies use colour; frogs signal their desires and location by sound; and moths can smell the opposite sex from over a kilometre away. Many birds, spiders, and chimpanzees communicate their sexual availability with dance. Birds have developed complex songs to proclaim a sexual territory and attract a mate, and wood quail have taken it to the point of singing in harmony. Bower birds have developed not only the capacity to build but to decorate in order to communicate with a sexual partner. Most animals coordinate their sexual activity to ensure that their offspring will be born at a time when food is plentiful. Ninety percent of birds are monogamous in a breeding cycle and many are monogamous for life. Sex has developed a multitude of rituals designed to build and maintain sexual tension, such as the clash and clatter of the beaks of gannets and albatross prior to mating.

The need for physical mating has led to the development of courtship and emotional bonding between mating pairs throughout much of the animal kingdom, particularly among birds and mammals. And while these functions relate primarily to the survival of the species, their effect is much grander. In their fullest expression these functions represent some of the finest attributes of life: dance, song, emotional bonding, commitment, and intimacy. Sex has developed intimacy as surely as it promotes long-term survival. Which brings us to our species.

While I would argue that the emotional and intellectual capacities of plants and animals are generally underestimated, I think it’s reasonable to assume that humanity represents the current evolutionary peak of these faculties, and that we are capable of a greater level of intimacy than any other species. The billion years of sexual evolutionary history that stretches behind us is undoubtedly responsible, but there is one particular development, one that is unique to humans, that strengthens the assumption – and it is a by-product of the evolutionary changes to the configuration of our hips and legs.

In the last stages of the evolutionary development that enabled our ancestors to leave the trees and walk and run upright, and do these things well, a wonderful thing happened: changes were made to our hips, leg bones, and muscles, which set us apart from other primates. These changes enabled a break, for the first time, from the near-universal rear-entry position for mating. Think about everything you’ve ever seen on the farm, in the wild, or in nature documentaries – from grasshoppers to doves, and from wombats to elephants – reproductive sex is always from the rear. The skeletal changes required for upright walking and running had the additional benefit of enabling front-to-front sex for the first time; and suddenly two intimate acts were possible simultaneously – intercourse and eye contact.

It takes a broad view of evolution to see it in terms of emotional capacity, but any capacity – physical, emotional, or intellectual – that leads to successful mating and the survival of offspring will be selected and promoted by evolution. So the question becomes: does intimacy lead to successful mating and survival of offspring? I would be surprised if it didn’t.

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