WEATHER »

On Ends and Endings

Sexual Selection and Evolution


Monday, February 27, 2012

I like big butts and I cannot lie.” – Sir Mixalot, “Baby Got Back” (1992)

Have you thought much about the evolution of the human butt? Neither had I until recently.

Survival of the Prettiest, by Nancy Etcoff, a psychologist at Harvard Medical School, is a great summary of the current science on human evolution and standards of beauty. The main surprise is that many aspects of beauty are not entirely in the eye of the beholder. In other words, many aspects of human beauty are common to all cultures and all times. Contrary to popular wisdom, preferences by men for women’s features such as large eyes, small chins, good skin, long lush hair, and an hourglass figure are common to all cultures studied so far. Similarly, preferences by women for men’s features such as a solid jaw, broad shoulders, good skin, and nice hair also seem to be common to all cultures.

Tam Hunt

Preference for a certain butt type is not, however, one of these universal features. Some do like big butts! And some like small butts. Our culture generally prizes a relatively small taut butt as the ideal, but there is quite a lot of variation in preferences even in our culture. Compare Kate Moss to Beyoncé and we get a feel for the variety in judgments about this particular aspect of beauty (forgive me if I focus on female body parts in this essay).

Beauty preferences and habits of cultures not our own can, especially when taken to the extreme, seem bizarre. The Hottentots, for example, were and are known for having enormous behinds. This fact became well known in England in the early 19th Century due to an unfortunate episode wherein the “Hottentot Venus,” Sara Baartman, a Khoi tribeswoman from South Africa, was displayed to the public in the nude at various venues in England over a period of about five years. Of particular fascination to anatomists and other scientists at the time, as well as the general public, was the accompanying enlarged labia minora, which apparently hung down quite a ways and confused early European explorers as to the nature of the body part on display. Google for further juicy details if you’re interested.

I’ve studied biology since my early teens and have always found questions about evolution fascinating. But it wasn’t until recently that I began thinking deeply about “sexual selection,” a term Darwin invented to distinguish the power of mating competition and choice from the environmental forces that define “natural selection.” This topic isn’t just a titillating aside to discussions about natural selection and evolution. Sexual selection is, in fact, central to evolution.

For example, an interesting debate is taking place among biologists with respect to the evolution of human hairlessness – or relative hairlessness. Racial differences in hairiness, and individual differences, are obviously quite pronounced. So too is taste for hairlessness or not – though the clear trend in all cultures today is toward women being hairless except for the hair on their head. Female taste for hair on men is a bit more varied, with some women in various cultures still preferring a good coat of chest hair, etc., but the more common trend seems to be toward relative hairlessness of men too. Why is there such variety in human hair/fur? One increasingly accepted answer: because we prefer less hair. In other words, we are, with each generation, expressing our sexual preferences for less hairy humans and, accordingly, each new generation is being born with less and less body hair. This is known as “sexual selection.”

Sexual selection is the evolutionary force resulting from competition for mates and – crucially – mate choice. The prototypical example is the peacock’s tail. Why is it so large and beautiful? Simply put: because peahens love a large and colorful tail in their guy. Darwin highlighted this force of nature in his second major work on evolution, The Descent of Man, and Selection in Relation to Sex, first published in 1871, twelve years after On the Origin of Species.

Geoffrey Miller, an evolutionary psychologist at UCLA, describes the checkered history of the theory of sexual selection in his entertaining and insightful book, The Mating Mind: “It was one thing for a generalized Nature to replace God as the creative force. It was much more radical [with sexual selection theory] to replace an omniscient Creator with the pebble-sized brains of lower animals lusting after one another. Sexual selection was not only atheism, but indecent atheism.” (One doesn’t have to be an atheist, of course, to believe in evolution, as I’ve written about in previous columns).

Human evolution has most likely been far more subject to sexual selection in our recent history than to other forces of evolution. The best evidence for this is the broad variety of tastes in many aspects of beauty that we see around the world – separate from the universal human tastes I described above. Why do Nordic Europeans look so different than Chinese, and why do they both look so different than sub-Saharan Africans? There are many reasons for these differences, but sexual selection has surely had a large role in these largely cosmetic changes (the genetic differences in the various types of humans are extremely small, but since we are so visually-oriented we tend to exaggerate the differences). In other words: mate choice has probably had a large role in shaping many of our modern-day features, such as butts and other obvious physical features such as hair, eyes, breasts, etc.

Miller concurs, and writes about the human butt: “Women’s breasts and buttocks did not evolve because hominid men happened to develop some arbitrary fixation on hemispheres as Platonic ideals of beauty. They evolved as reliable indicators of youth, health, fertility, symmetry and adequate fat reserve.”

I agree that there are many utilitarian indicators in particular aspects of human evolution, including the shape of secondary sexual characteristics like breasts and butts. But one thing Miller passes over, and most evolutionary biologists also pass over, is the purely aesthetic aspect of sexual selection that Darwin himself stressed. Many features that evolved through sexual selection evolved, it seems when we consider the body of evidence, purely because the opposite sex liked those features, independent of any utilitarian benefits to those features.

When we consider that various birds of paradise in very similar climates have evolved quite different plumage in a relatively short period of time – but equally ornate – it is hard to find any reason as to why such differences would have evolved other than that the female taste for this plumage differed in certain ways in different areas.

Darwin agreed with my point here, even though the modern trend among biologists is to discount the role of aesthetics in sexual selection. Darwin mentioned in many passages in The Descent of Man the “choice” exerted by birds and other creatures in sexual selection. He was very clear that he was attributing mind and aesthetic powers to non-human creatures. Here’s one example: “On the whole, birds appear to be the most aesthetic of all animals, excepting of course man, and have nearly the same taste for the beautiful as we have.”

The Future of Human Evolution: Turning our gaze from the past toward the future of evolution, where are we going as a species? The quick thinking is that we aren’t evolving physically very much anymore because we’re so pampered, in a relative sense. That is, with modern medicine, technology, and supportive social structures, we face far less environmental pressures than we have for the vast majority of our history. But this quick thinking is very likely wrong. There is plenty of room for debate, but it’s becoming clear that human physical evolution is speeding up in the modern era, not slowing down. Some biologists have suggested rates of evolution in humans at up to 10,000 times the historical average. Why?

Well, there seems to be a positive feedback process in evolution: as consciousness becomes more complex, as it has in humans in particular in recent millennia, that consciousness exerts more pressure back on the evolutionary process that produced it. It’s a positive feedback loop, and like all such loops, it speeds up over time.

The more interesting aspect of modern evolution is not, however, biological evolution but cultural and technological evolution. We are now at the point that cultural and technological evolution are far more powerful forces than traditional evolutionary forces. Our technology is at the point that we will soon be shaping ourselves and our progeny in increasingly important ways. In other words, technological evolution is now at the point that it can take over much of the role that biological evolution has played for billions of years. We can select the gender of our children now, and can also select specific traits within limits. In coming years, this trend will become far more pronounced.

This increasing power to shape our own evolution is part of the same evolutionary process that has always been present, but it has taken a huge jump in rapidity with the advent of modern technology, made possible by another similar jump a few million years ago: the rapid growth of the human brain. Evolution does seem to occur in leaps and bounds, with long periods of stasis in between (an idea known as “punctuated equilibrium”).

Armed with modern technology, we’ll soon be able to design the perfect butt for each of our tastes. And every other body part with it…

The Deep Span of Evolution: The more important trend in evolution does not, alas, concern our body parts. Rather, it concerns the far longer span of future history and the ongoing evolution of consciousness. Where are we going when we look toward the very distant future? Where does it all end? Does it have to end?

Pierre Teilhard de Chardin, an influential French anthropologist and philosopher who was also a Jesuit priest, defined the “modern man” as one who sees evolutionary trajectories all around, not static points or objects in time. Teilhard’s vision was one of an evolutionary spirituality, an integration of evolutionary theory with spirituality. His primary work is the visionary book, The Phenomenon of Man, written in 1940 but published in English for the first time in 1955.

Teilhard also described “the Omega Point,” a synonym for God, or “the Summit,” which I’ve discussed in previous essays. But the Omega Point is different than traditional notions of God because Omega evolves. Omega is here now and is the sum total of all conscious beings that already exist. Just as the cells in our body create a unity (us) out of the plurality (the trillions of cells in our bodies), we collectively create, under Teilhard’s thinking, a far higher-level entity through our combination. Part of this process is the ongoing creation of the “noösphere,” the realm of thought swirling already over our heads with our radio and TV waves, and now incarnating as the Internet, in all its glory and transformational power.

For Teilhard, there was an end point to this process of God’s – and our – evolution. Once the energy breathed into creation at the beginning of our universe has been exhausted through the ongoing interiorization of matter (another way of describing the complexification of consciousness), and the achievement of perfect consciousness in Omega’s final form, then it all ends.

This idea is particularly relevant in the year of our Lord 2012. There are various cultural threads suggesting that we’re at an end point to history. Teilhard himself said nothing about 2012, to my knowledge, and it seems clear that the end of history he envisioned will take place far in the future. However, the end of the Mayan calendar, Terrence McKenna’s Shockwave model, and some other ideas popular among the Burning Man set and New Age types suggest that we’re in for a rough ride this year.

I’m part of the Burning Man set (I’ve been three times and will be going again this year, with ticket already in hand – my condolences to everyone who failed to win in the lottery this year), but I view 2012 as a time of major transformation, not doom and gloom. Just as death can be viewed as an ending or as a transformation, I think we’re in for major transformation at this point in our history. My feeling is that Teilhard got this idea wrong: There is no end point to evolution, at least not for the reasons he supposed. I can respect and admire his edifice of thought but still reject the notion of an end-point to evolution.

Nor do I think there’s anything special about 2012 – except for the cultural significance we collectively give it, kind of like the power of financial markets or currency more generally. Rather, I think we’re in a time of rapid change and turmoil that has been building for millennia, and that will ultimately lead to something even better than we have today. There may be some real speed bumps in the road ahead, but the road does seem to me to be winding its way upward to a beautiful house on a hill. With a great view.

We can, in this vision of the future, look forward not only to the perfect butt but also to helping God itself evolve – because we are part and parcel of God – as we all unfold forward in a never-ending process of improvement and creative exploration.

Related Links