Saturday, February 14, 2009

Scientists Agree: It's in His Kiss | Wired Science from Wired.com

Scientists Agree: It's in His Kiss | Wired Science from Wired.com

And according to experts in this field (yes, there are at least three of them), the 60's pop song got it right: It really is in his kiss.

"Kissing is a mechanism for mate choice and mate assessment," Helen Fisher, a Biological Anthropologist from Rutgers University here at the American Association for the Advancement of Science, said to a press conference crowded with science journalists hoping for a story or, perhaps, some advice.

Over 90 percent of human society engages in what, if you get right down to it, seems like a very strange thing to do: putting faces together and trading spit. But because it is so pervasive, scientists think there must be a good reason for it, some kind of evolutionary advantage. And humans aren't alone in this ritual. Chimpanzees kiss, foxes and dogs lick each other's faces, some birds tap their bills together, and elephants put their trunks in each other's mouths.

Humans have been kissing for ages. "Many kisses, particularly in the Roman novels, are slobbery," said Donald Lateiner of Ohio Wesleyan University in Delaware who studies the history of kissing. "Every time that the past is excavated at Pompeii, there is good a chance there will be some additional data on sexual customs, if not kissing."

So what's all the making out about? It may have to do with that elusive but essential ingredient to true love that we call chemistry. It turns out, it may not be that elusive after all. It may just actually be...chemistry.

Saliva is like a chemical cocktail, and hooking up may have evolved to help us quickly tell if someone is a good mate or not, Fisher said.

After all, haven't we all been attracted to someone and then the first kiss just killed it? It might be because he didn't have the right stuff in his spit. Lots of hormones are present in differing quantities in our saliva, and they may serve several romantic purposes.

"There's evidence that saliva has testosterone in it, and there's also evidence that men like sloppier kisses with more open mouth," Fisher said. "That suggests to me that they are unconsciously trying to transfer testosterone to trigger the sex drive in women."

[...]

And there may be more to this chemical assessment than just kissing, Fisher said. "I think kissing is the tip of the ice berg. I think we'll find that all kinds of other chemical systems are in play that we don't know about."

Fisher says she has found from other scientists' research and from her own analysis of statistics on 40,000 people on the dating Web site Chemistry.com that there are four dimensions of temperaments, or biologically based traits, and each is associated with different chemical systems in the brain: Dopamine is associated with traits like novelty seeking, risk taking, curiosity and creativity; serotonin was linked to calm, caution cooperation, loyalty, and tradition; testosterone with decisiveness and emotional containment; and estrogen lumped together with oxytocin was linked to nurturing, patience and social skills.

So Fisher devised a questionnaire and gave it to 28,000 people on Chemistry.com to see if how strongly people express each of these systems affects their partner choice.

"It now appears that we are drawn to people with particular biological profiles," she said. And the kiss may be how we assess someone's profile.

This drew the obvious question from a reporter: "Is it true that opposites attract?"

Well, that depends on the person she said. Those adventurous ones who express dopamine strongly preferred people like themselves, and the same was true for the more traditional, serotonin expressers. But those high in testosterone preferred more estrogen and vice versa.

Cooking Has Been Both Boon and Bane for Humans | Wired Science from Wired.com

Cooking Has Been Both Boon and Bane for Humans | Wired Science from Wired.com

CHICAGO — Raw-food devotees take note: Your diet is not in any way natural. Humans are as adapted to cooking our food as cows are to eating grass, or ticks are to sucking blood.

"Cooking is a human universal," said Harvard primatologist Richard Wrangham at the American Association for the Advancement of Science meeting here Friday. While cooking kills parasites and other pathogens, Wrangham believes this health benefit is not its primary contribution.

"The fundamental importance of cooking is that it provides increased sources of energy," he said.

And that boost may be what facilitated the leap in size between Homo erectus and modern Homo sapiens. But, cooking may also have helped some modern humans into an obesity epidemic.

Wrangham cited data showing that cooking increases the body's ability to digest starches (as found, for example, in bread, potatoes and bananas). Only about 50 percent of raw starches are digested, compared to 90 percent of cooked ones. The trend, and the numbers, are similar for protein: from 50 to 65 percent digestibility raw to better than 90 percent cooked.

The reason: Heat breaks down starch and protein molecules, making it easier for digestive enzymes to attack them.

Cooking also softens up food, meaning the body doesn't have to use as much energy to process it. We spend less time chewing cooked food, and we secrete fewer chemicals to break it down. A recent study gave rats identical diets, except half the animals were served softened pellets and the other half received hard ones. After 25 weeks, the rats eating soft food were significantly heavier and had 30 percent more body fat, Wrangham said.

We cook almost everything, except some fruits and vegetables, and we need to. People on raw-food diets lose weight almost without fail, because they can't access enough calories. Half of all women eating exclusively raw foods become so thin that they stop menstruating, he said.

And our bodies show the imprint of this dependence on cooking. We have small, soft teeth, and our guts are smaller than those of any other primate relative to body size.

These traits go back a long way. Humans have controlled fire for at least 200,000 years, and perhaps for much longer. In fact, Wrangham speculates that cooking may have spurred a huge leap in the evolution of H. sapiens' ancestor, H. erectus. He's written a book on the idea called Catching Fire: How Cooking Made Us Human, which will come out in June.

About 1.8 million years ago, the brain of H. erectus ballooned and its body got bigger. Its arms got shorter, its legs longer. It became, in short, less of an ape and more of a human. Mankind has not undergone anything approaching this anatomical transformation since.

"No really big changes are seen after H. erectus," Wrangham said.

Looking for Love In All the Right Alleles | Wired Science from Wired.com

Looking for Love In All the Right Alleles | Wired Science from Wired.com

People may naturally be attracted to mates with HLA profiles different from their own, ostensibly guaranteeing the hybrid vigor of their offspring's immune systems -- and also providing a spark that will last through good times and bad.

"Proper age, similar life goals and ideas, education levels -- all of these things have to fit. And on top of that, you need to be biologically compatible," said Tamara Brown, managing director of GenePartner.

But not everyone is convinced that scientists can read the genome of love.

"These kinds of ideas are not as crazy as they often sound, but before you start trying to sell this kind of thing, we'd like to have solid evidence," said Dustin Penn, a behavioral biologist at the Konrad Lorenz Institute for Ethology. "There's some supporting evidence, but it's mixed."

The science of HLA love started with Swiss biologist Claus Wedekind, who in 1995 found that women preferred the smell of T-shirts worn by men with HLA profiles dissimilar to their own. The findings were replicated, and a later study showed that couples with similar profiles were less likely to have children and more likely to cheat on each other.

GenePartner claims to have pushed that research forward. "Is there a specific pattern? That's what we found. That's the main strength of the algorithm," Brown said.

Science News / All In The Family

Science News / All In The Family

Could there be genetic benefits to marrying distant cousins for animals and humans?


Kissing cousins

It's no secret that humans interbreed too. Charles Darwin married his first cousin, Emma Wedgewood. More recently, a 1997 study of Pakistani hospitals found that three out of five marriages were between first cousins, while a study of one South Indian city found that one-fifth of marriages occurred between uncles and nieces and a third between first cousins.

But close inbreeding comes with a high cost for humans. "First cousins, when they have babies—it's like a textbook example—tend to have higher mortality," Zamudio says. In contrast, scientists know little about the effects of inbreeding between more distantly related couples—third cousins and beyond. But recent work on Icelanders suggests that some family loving might be a good thing.

A team of researchers at the Icelandic firm deCODE genetics sifted through 165 years of genealogy data from 160,000 couples. Pairs who shared a great-great-grandparent—third cousins—tended to have more children and grandchildren than did more distantly related spouses. For instance, women born between 1925 and 1949 who married third cousins had 3.3 kids and 6.6 grandkids, on average. Women who married eighth cousins bore 2.5 children and 4.9 grandchildren. Yet the study, published in the Feb. 8 Science, doesn't give carte blanche to forbidden love. More closely related couples—first and second cousins—had fewer children than less-related couples, and the inbred kids died at a younger age.

"That was a very nice confirmation of work people have done with other animals," says Bateson, who showed in the 1970s that Japanese quail prefer first cousins over brothers and sisters and over less-related birds. He and other researchers stress that animals in the wild must balance the pluses and minuses of inbreeding and outbreeding to do best for their children.