Why we fuck

1. Why Sex?
A biologist explains the evolutionary advantage of sex, and why we're not all asexual clones.
By Britt Peterson (from seed magazine)

Sex—it gives us diseases, sucks away our energy, clouds our judgment and doesn't even transfer our genes that efficiently anyway. So why have humans and most other animals evolved this bizarre, slightly dirty quirk of sexual reproduction? Why haven't we all taken Woody Allen 's advice, and evolved to reproduce with someone we love, instead?

Evolutionary biologists have pondered this question since the late 19th century, when German biologist August Weismann proposed that sexual reproduction evolved to create variety amongst siblings. A new understanding of genomics in the 20th century led to refinements of his theory, and allowed new ones to emerge. The so-called Red Queen hypothesis, named after a character from Lewis Carroll 's Through the Looking Glass , for example, explains sex as an adaptation that helps sexual reproducers resist parasites. According to this hypothesis, sexual reproduction—which can create variation from generation to generation evolved to allow species to develop adaptations to avoid their specific parasites.

Another explanation, the mutational deterministic hypothesis (MDH) proposed by Alexey Kondrashov in the late 1980s, posits that sex works to combine deleterious mutations. As generations pass, the mutations act upon one another in an exponentially harmful build-up that finally works to kill the organism, killing the mutations in the process. In other words, certain lineages act as mutation traps, eventually being eliminated to protect the rest of the species.

While MDH is probably the most widely accepted theory that attempts to describe sexual reproduction's prevalence, it has never been proven. Recently, University of Houston biologist Ricardo Azevedo created a computer model of genetic interactions to study the evolution of a simple organism under several sets of conditions. He and colleague Christina Burch of the University of North Carolina determined that sexual reproduction is self-reinforcing, and that it can lead to a genetic phenomenon called negative epistasis, an exponentially harmful accumulation of mutations that's a proposed precondition of MDH. While this research does not provide a conclusive proof for MDH, it may help future scientists solve the enduring mystery of sexual reproduction's evolution.

Seed spoke with Azevedo about his research, and asked him the burning question: Why on Earth aren't we all asexual mutants?

Can you explain, in evolutionary terms, why sex is such a problem?
Males go out of their way to persuade females to mate with them. All this expends a lot of energy and a lot of resources, and so on a strictly utilitarian view, you would think that asexuals would have a direct advantage.

So what would the alternative be?
If you imagine, for example, in a population like the human population, if there was a mutation that turned a female into an asexually reproducing female that could just have female offspring without sexual encounters, then that single individual would start a clone of females that would, per capita, have twice the reproductive rate of the normal human population. You would think that sexual populations could be invaded by asexual mutants, and that sexuality could be displaced by asexuals.

But it hasn't, clearly. Or if it has, no one's told me yet.
No, [asexuality] seems to be a dead end, somehow, evolutionarily. When asexuals appear, they don't last very long. They can have a short-term advantage, maybe, and run for a little while. But at some point something happens to them and they disappear. If the MDH or a similar theory is correct, they simply accumulate harmful mutations and die out.

So one theory for why asexuals aren't as selectively successful as sexuals is MDH. I know it's based on the assumption that negative epistasis will affect an organism. What is negative epistasis?
RA: Imagine that on average a harmful mutation will decrease fitness by about 5%. If you imagine now an organism with successive rounds of harmful mutation, you'd imagine that if the mutations don't have anything to do with each other, then every time you add the next harmful mutation, you'll just decrease fitness by another 5%. The first knocks it down by 5%, the second knocks it down by another 5%, and so on. It just keeps going that way. The alternative then is if the mutations interact with each other. Negative epistasis is the case where, as you add more and more mutations, the effects become progressively worse. So first you lose five, the second you lose 10, the third you lose 15, and it just keeps getting worse. So after a few rounds of mutations, you're essentially dead, because the mutations accumulate.

So according to MDH, sex has evolved to isolate and destroy mutations. How does this make us more effective than the asexual mutants?
One of the things that sexual reproduction can do is produce individuals every generation that concentrate many mutations because sex can recombine different genomes. Asexuals find it very difficult to fight against [mutations], because they cannot recombine and so they cannot produce these individuals with either fewer mutations or more mutations. They can only live with what they have.

How has your research helped provide evidence for MDH?
[Our results showed that] in conditions that select for insensitivity to mutation, sexual reproduction adds to this selection and then leads to the evolution of negative epistasis as a byproduct. So, if these conditions are realistic in nature, it suggests that negative epistasis should be out there, in many organisms and in many bases.

Finally, what should all of this mean about how humans view sex, in a social way? Does this make you frightened of sex?
No, not based on our work, except perhaps, in a strictly scientific sense. The origin and maintenance of sex is still a very difficult question that will not be solved easily. One thing to note is that, in an evolutionary sense, humans and other mammals have no choice in the matter; due to genomic imprinting, it's unlikely that we'll ever be taken over by asexual clones.


2. Men (And Sometimes Women) Lure Mates Creatively -- by Emily Anthes (from seed magazine)

During mating season, male bowerbirds make elaborate ground-level structures out of sticks, moss and leaves, then decorate these bowers with colorful flowers, stones and shells. They sometimes even "paint" them with berries.

When the time comes, the females choose to mate with the males that have built the biggest, most symmetric and best decorated nests.

While male bowerbirds' creative displays have a clear function, the purpose of human creativity is not as well understood. Some scientists theorize that problem solving, which is one facet of creativity, confers a survival advantage and probably evolved via natural selection.

But a new study by Arizona State University researchers provides evidence that creativity could also be the result of a complementary process known as sexual selection.

According to sexual selection, traits attractive in a mate will become more common over time, as the individual animals that display those traits pass on their genes more often than animals that don't. Sexual selection can lead to traits that don't have a direct survival advantage but serve to advertise the fitness of their bearer's genes.

"Creativity might be this kind of response that is designed not just to enhance our reproductive potential by making us better problem solvers but by making us more attractive to prospective mates," said Robert Cialdini, an author of the study, published in the July issue of the Journal of Personality and Social Psychology .

To test that idea, Cialdini, along with colleagues Vladas Griskevicius and Douglas Kenrick, recruited 615 subjects and provided them with various romantic prompts. Some subjects were shown pictures of attractive members of the opposite sex while others were asked to imagine certain romantic scenarios such as envisioning meeting a romantic interest on the final day of a vacation or being with a long-term partner, who was sometimes described as being loyal and committed. After each of these prompts, subjects were asked to perform tasks used to asses their creativity, such as writing descriptions of uncaptioned cartoons, interpreting abstract pictures and taking a standardized creativity test.

The men became more creative whether they were looking at photos, imagining short-term liaisons or envisioning a long-term partner. The women, however, showed substantial increases in creativity only when they imagined devoted long-term partners.

"Men become lures through creativity at the drop of a hat at the possibility of a romantic liason," Cialdini said. "Women reserve that lure for the kind of partner who is likely to be a good match for her and a long-term committed relationship member."

In most animal species, males display sexually selected traits while females select for them—the classic example being the brightly colored tail of the peacock, which is displayed only by males. This sort of female-mandated selection is most commonly seen in species where mothers contribute much more to their offspring than fathers do.

"Women need to be more selective about the mates that they accept," Cialdini said. "They have to invest much more in the consequences of any act of conception than men do."

Martie Haselton, an evolutionary psychologist at the University of California, Los Angeles , said the study's findings about the relationship between romance and creativity—and about males' disproportionate display of romance-inspired creativity—provide a significant boost to the sexual selection theory of creativity.

"This is some of the strongest evidence for that I've seen," she said.

The theory may also help explain the relationship between artists and their muses.

"That's something that had always intrigued me," Cialdini said. "It seemed like muses were invariably women, and the artists were invariably men. What's that all about?"

Cialdini's finding that an image of an attractive member of the opposite sex is likely to inspire heightened creativity in men and not women may explain the discrepancy, though he notes that muses aren't exclusive to male artists: Poet Elizabeth Barrett Browning found inspiration in her husband, fellow poet Robert Browning.

Though both male and female artists can have muses, the inspirer's characteristics tend to be different, Cialdini said.

"A committed, highly valued partner will spur women to heights of creativity," he said. "For men, they tend to be mistresses."


3. Getting Physical
Einstein, Feynman and other famous swingers.
By Joshua Roebke (from seedmagazine.com)

Late last year, researchers in England published a study purporting to establish a link between creative output and number of sexual partners. As the lead author (under)stated, “Creative people are often considered to be very attractive and get lots of attention as a result.”

The theoretical physicists of the 20th century were no exception. Promiscuous chasers by profession, physicists ever-pursue objects that lie partially hidden to the immediate senses, but are evidently there behind nature’s many layers. The best physicists are able to tease a peek beneath all that partially-covered exterior, as any pickup artist would: with a mix of cleverness and straightforward arrogance. This is hardly just simple metaphor; for many of the greatest physicists, this libertine modus operandi also fueled their private lives.

Schrödinger, Curie, Einstein, Feynman, Oppenheimer…the finest names of pre-Cold War 20th-century physics, some of whom gave us the most concise theories ever posited, form a roster of lamentable philanderers. Albert Einstein was completely “given to flirtation” and had legions of affairs. Caltech professor and bestselling raconteur Richard Feynman was probably the only Nobel Prize winner to befriend porn stars, claim a foolproof manner for bedding women and do his calculations on napkins in strip clubs. And it wasn’t just the guys: Marie Curie was relentlessly hounded by the press for seducing away her late-husband’s former student from his wife and kids.

“Libertines, both male and female, have always been around in math and physics,” says Jennifer Ouellette , who writes on physics history and is associate editor of the American Physical Society ’s newsletter. Yet today, while physicists still spend day and night chasing nature, the era of chasing skirts — or knickers—seems to have passed. Where have all the physics playb—er, sociable persons gone?

Between the world wars, physicists hunted the big ideas and had the big personalities—and sex drives—to match. They worked and played under a unique confluence of circumstance. The sexual norms of the time, their status, the sexiness of their projects and achievements all conspired to make the top physicists supremely desirable.

The most shameless cad of the group was Richard Feynman. When he once nearly crashed his car while eyeing a passing beauty, his only excuse was, “I only see the women, the rest is all a blur.” He even kept a picture in his office of one acquaintance, buxom adult film star Candi Samples, signed, “To Big Dick, Love from Candi.”

Remarkably, some physicists’ trysts seem to have actually led to physical insight: While once floundering on a problem, Erwin Schrödinger shacked up in an alpine villa for an extended holiday with “an old girlfriend” and, in the “late erotic outburst” that followed, produced the eponymous equation that would net him the Nobel.

At the atomic bomb project in Los Alamos , the assembled brain trust was as hard-partying as a troop of college kids on spring break. Weekends with the physicists were “big and brassy,” replete with poker and booze. They played so hard that the program tried to quarantine the women’s dorms; as one boss euphemized, “The girls had been doing a flourishing business of requiting the needs of our young men.” So many babies resulted that Robert Oppenheimer (or his boss, nobody’s really sure), himself having tried to run off with the wife of Linus Pauling and bed the wife of another colleague, was told to halt the extracurricular activities. (Oppenheimer didn’t.)

So what’s happened since? Not to bemoan the loss of machismo, but today’s physicists seem to lack that same rat-pack panache that old-school physicists brought to the blackboard. Considering the unparalleled prestige that the Atomic Era physicists enjoyed, it’s hardly astonishing that sexual power plays —like those that often transpire between an executive and assistant, or even a president and an intern —could have resulted. And though modern theoreticians still pursue big ideas, their intellectual forebears revealed so many of nature’s broad physical features that, now, only the finer areas are left to explore.

Ouellette points to another possible explanation: “This stuff still goes on, we just don’t hear about it. The history books on the great physics personalities of the late 20th century have yet to be written.” She points to a famous professor whom “everyone knows ditched” one woman for another: “it’s gossiped about, but you never read about it [because] the science is what really matters.” There’s also Stephen Hawking, whose affair was detailed in the British tabloid. Perhaps there are others.

And perhaps, with the new Large Hadron Collider ready to go online next year—if physics is now “just another discipline,” as Nature recently editorialized—its time will come again. In the meantime, it might help to remember Richard Feynman’s truth-laden maxim, “Physics is like sex: Sure, it may give some practical results but that’s not why we do it.”