Female Choice Key to Evolutionary Shift to Modern Family

It is a question that has puzzled evolutionary biologists for years: Why did we stop being promiscuous and decide to settle down to start families?

Sergey Gavrilets, professor of ecology and evolutionary biology at the University of Tennessee, Knoxville, may have found the answer, and it lies in the power of female choice. The study reveals how females chose their mates played a critical role in human evolution by leading to monogamous relationships, which laid the foundation for the institution of the modern family.

Using mathematical modeling, the associate director for scientific activities at the National Institute for Mathematical and Biological Synthesis (NIMBioS) at UT has discovered that the transformation may have occurred when early-hominid females started choosing males who were good providers.

Gavrilets' findings are published in the Proceedings of the National Academy of Sciences.

The "sexual revolution" entailed males first competing with other males for dominance, as a way to get matings. However, low-ranked males—and eventually all males except those with the highest societal stature—began supplying females with provisions in what is called "food-for-mating" to get a leg up on the competition. Females showed preference for the "provisioning" males, leading males' energy to be spent on providing for females and females becoming increasingly faithful. This spurred self-domestication and the modern family as we know it today.

"This change has confounded scientists for a long time because many species would be much better off evolutionarily if the effort spent on males competing for mates was redirected towards increasing female fertility or survivorship of their offspring," said Gavrilets.

The study demonstrates mathematically that the most commonly proposed theories for the transition to human pair bonding—or coupling—are not biologically feasible.

However, the study advances a new model showing that the transition to pair-bonding can occur when female choice and faithfulness, among other factors, are included. The result is an increased emphasis on males provisioning females over male competition for mating.

"The study reveals that female choice played a crucial role in human evolution," said Gavrilets.

According to Gavrilets, the transition to coupling has opened the path to intensified male parental investment, which was a breakthrough adaptation with multiple anatomical, behavioral and physiological consequences for early hominids and for all of their descendants. It shifted the dynamic away from males competing with each other for sex to males competing with each other to see who is a better provider to get better mates.

"Pair bonding laid the foundation for a later emergence of the institution of the modern family," said Gavrilets.

Source: University of Tennessee [May 30, 2012]

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Researchers create synthetic DNA/RNA that can evolve

Researchers have created artificial genetic material known as Xenonucleic acids, or XNAs, that can store information and evolve over generations in a comparable way to DNA. 

The research, reported Friday in the journal Science, has implications for the fields of molecular medicine and biotechnology, and sheds new light on how molecules first replicated and assembled into life billions of years ago. 

Living systems owe their existence to the information-carrying molecules DNA and RNA.  These fundamental chemical forms have two features essential for life: they display heredity, meaning they can encode and pass on genetic information, and they can adapt over time. 

Whether these traits could be performed by molecules other than DNA and RNA has been a long-debated issue. 

For the current study, an international team of researchers developed chemical procedures to convert DNA and RNA into six genetic polymers known as XNAs.  The process switches the deoxyribose and ribose (the “d” and “r” in DNA and RNA) for other molecules. 

The researchers demonstrated for the first time that all six XNAs could form a double helix with DNA, and were more stable than natural genetic material.  Moreover, one of these XNAs, a molecule known as anhydrohexitol nucleic acid, or HNA, was capable of undergoing directed evolution and folding into biologically useful forms. 

Philipp Holliger of MRC Laboratory of Molecular Biology in Cambridge, the study’s senior author, said the work demonstrated that heredity and evolution were possible using alternatives to natural genetic material. 

“There is nothing Goldilocks about DNA and RNA,” he told Science. 

“There is no overwhelming functional imperative for genetic systems or biology to be based on these two nucleic acids.” 

Both RNA and DNA embed data in their sequences of four nucleotides.  This information is vital for conferring hereditary traits and for supplying the coded recipe essential for building proteins from the 20 naturally occurring amino acids.  However, precisely how and when this system began remains one of the most perplexing and hotly contested areas of biology. 

According to one hypothesis, the simpler RNA molecule preceded DNA as the original informational conduit. The RNA world hypothesis proposes that the earliest examples of life were based on RNA and simple proteins.  Because of RNA’s great versatility—it is not only capable of carrying genetic information but also of catalyzing chemical reactions like an enzyme—it is believed by many to have supported pre-cellular life. 

Nevertheless, the spontaneous arrival of RNA through a sequence of purely random mixing events of primitive chemicals was, at the very least, an unlikely occurrence. 

“This is a big question,” said study leader John Chaput, a researcher at Arizona State University’s Biodesign Institute. 

“If the RNA world existed, how did it come into existence? Was it spontaneously produced, or was it the product of something that was even simpler than RNA?” 

This pre-RNA world hypothesis has been gaining ground, primarily through study of XNAs, which provide plausible alternatives to the current biological system and could have acted as chemical stepping-stones to the eventual emergence of life. 

Threose nucleic acid, or TNA, for example, is one candidate for this critical intermediary role. 

“TNA does some interesting things,” Chaput said, noting the molecule’s capacity to bind with RNA through antiparallel Watson-Crick base pairing. 

“This property provides a model for how XNAs could have transferred information from the pre-RNA world to the RNA world.” 

Nucleic acid molecules, including DNA and RNA, consist of 3 chemical components: a sugar group, a triphosphate backbone and combinations of the four nucleic acids.  By manipulating these structural elements, researchers can engineer XNA molecules with unique properties. 

However, in order for any of these molecules to have acted as a precursor to RNA in the pre-biotic epoch, they would need to have been able to transfer and recover their information from RNA. To do this, specialized enzymes, known as polymerases are required. 

And while nature has made DNA and RNA polymerases capable of reading, transcribing and reverse transcribing normal nucleic acid sequences, no naturally occurring polymerases exist for XNA molecules. 

So the researchers, led by Holliger, painstakingly evolved synthetic polymerases that could copy DNA into XNA, and other polymerases that could copy XNA back into DNA. 

Ultimately, polymerases were found that transcribe and reverse-transcribe six different genetic systems: HNA, CeNA, LNA, ANA, FANA and TNA. The experiments demonstrated that these unnatural DNA sequences could be rendered into various XNAs when the polymerases were fed the appropriate XNA substrates. 

Using these enzymes as tools for molecular evolution, the team evolved the first example of an HNA aptamer through iterative rounds of selection and amplification.  Starting from a large pool of DNA sequences, a synthetic polymerase was used to copy the DNA library into HNA. The pool of HNA molecules was then incubated with an arbitrary target. The small fraction of molecules that bound the target were then separated from the unbound pool, reverse transcribed back into DNA with a second synthetic enzyme, and amplified by PCR. After many repeated rounds, HNAs were generated that bound HIV trans-activating response RNA (TAR) and hen egg lysosome (HEL), which were used as binding targets. 

“This is a synthetic Darwinian process,” Chaput said. 

“The same thing happens inside our cells, but this is done in vitro.” 

The method for producing XNA polymerases draws on Holliger’s pervious, path-breaking work, and uses cell-like synthetic compartments of water/oil emulsion to conduct directed evolution of enzymes, particularly polymerases. 

By isolating self-replication reactions from each other, the process greatly improves the accuracy and efficiency of polymerase evolution and replication. 

“What nobody had really done before,” Chaput said, “is to take those technologies and apply them to unnatural nucleic acids. ” 

Chaput said the study advances the case for a pre-RNA world, while revealing a new class of XNA aptamers capable of fulfilling many useful roles. 

And while many questions surrounding the origins of life remain, he is optimistic that solutions are coming into view. 

“Further down the road, through research like this, I think we’ll have enough information to begin to put the pieces of the puzzle together.” 

In an article accompanying the study in the journal Science, Gerald Joyce of the Scripps Research Institute wrote that “the work heralds the era of synthetic genetics, with implications for exobiology (life elsewhere in the Universe), biotechnology, and understanding of life itself”. 

However, he stressed that the work does not yet represent a full synthetic genetics platform. For that, a self-replicating system that does not require the DNA intermediary must be developed. 

If that happens, “construction of genetic systems based on alternative chemical platforms may ultimately lead to the synthesis of novel forms of life”. 

Source: RedOrbit [April 20, 2012]

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Teamwork linked to intelligence

Learning to work in teams may explain why humans evolved a bigger brain, according to a new study published on Wednesday. 

Learning to work in teams may explain why humans evolved a bigger brain [Credit: AFP]

Compared to his hominid predecessors, Homo sapiens is a cerebral giant, a riddle that scientists have long tried to solve. 

The answer, according to researchers in Ireland and Scotland, may lie in social interaction. 

Working with others helped Man to survive, but he had to develop a brain big enough to cope with all the social complexities, they believe. 

In a computer model, the team simulated the human brain, allowing a network of neurons to evolve in response to a series of social challenges. 

There were two scenarios. The first entailed two partners in crime who had been caught by the police, each having to decide whether or not to inform on the other. 

The second had two individuals trapped in a car in a snowdrift and having to weigh whether to cooperate to dig themselves out or just sit back and let the other do it. 

In both cases, the individual would gain more from selfishness. 

But the researchers were intrigued to find that as the brain evolved, the individual was likelier to choose to cooperate. 

"We cooperate in large groups of unrelated individuals quite frequently, and that requires cognitive abilities to keep track of who is doing what to you and change your behaviour accordingly," co-author Luke McNally of Dublin's Trinity College told AFP. 

McNally pointed out, though, that cooperation has a calculating side. We do it out of reciprocity. 

"If you cooperate and I cheat, then next time we interact you could decide: 'Oh well, he cheated last time, so I won't cooperate with him.' So basically you have to cooperate in order to receive cooperation in the future." 

McNally said teamwork and bigger brainpower fed off each other. 

"Transitions to cooperative, complex societies can drive the evolution of a bigger brain," he said. 

"Once greater levels of intelligence started to evolve, you saw cooperation going much higher." 

The study appears in Proceedings of the Royal Society B, a journal published by Britain's de-facto academy of sciences. 

Commenting on the paper, Robin Dunbar, an evolutionary anthropologist at Oxford University, said the findings were a valuable add to understanding brain evolution. 

But he said there were physiological limits to cooperation. 

Man would need a "house-sized brain" to take cooperation to a perfect level on a planet filled with humans. 

"Our current brain size limits the community size that we can manage ... that we feel we belong to," he said. 

Our comfortable "personal social network" is limited to about 150, and boosting that to 500 would require a doubling of the size of the brain. 

"In order to create greater social integration, greater social cohesion even on the size of France, never mind the size of the EU, never mind the planet, we probably have to find other ways of doing it" than wait for evolution, said Dunbar. 

Source: AFP [April 11, 2012]

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What Are Emotion Expressions For?

That cartoon scary face – wide eyes, ready to run – may have helped our primate ancestors survive in a dangerous wild, according to the authors of an article published in Current Directions in Psychological Science, a journal of the Association for Psychological Science. The authors present a way that fear and other facial expressions might have evolved and then come to signal a person’s feelings to the people around him. 

The basic idea, according to Azim F. Shariff of the University of Oregon, is that the specific facial expressions associated with each particular emotion evolved for some reason. Shariff cowrote the paper with Jessica L. Tracy of the University of British Columbia. So fear helps respond to threat, and the squinched-up nose and mouth of disgust make it harder for you to inhale anything poisonous drifting on the breeze. The outthrust chest of pride increases both testosterone production and lung capacity so you’re ready to take on anyone. Then, as social living became more important to the evolutionary success of certain species—most notably humans—the expressions evolved to serve a social role as well; so a happy face, for example, communicates a lack of threat and an ashamed face communicates your desire to appease. 

The research is based in part on work from the last several decades showing that some emotional expressions are universal—even in remote areas with no exposure to Western media, people know what a scared face and a sad face look like, Shariff says. This type of evidence makes it unlikely that expressions were social constructs, invented in Western Europe, which then spread to the rest of the world. 

And it’s not just across cultures, but across species. “We seem to share a number of similar expressions, including pride, with chimpanzees and other apes,” Shariff says. This suggests that the expressions appeared first in a common ancestor. 

The theory that emotional facial expressions evolved as a physiological part of the response to a particular situation has been somewhat controversial in psychology; another article in the same issue of Current Directions in Psychological Science argues that the evidence on how emotions evolved is not conclusive. 

Shariff and Tracy agree that more research is needed to support some of their claims, but that, “A lot of what we’re proposing here would not be all that controversial to other biologists,” Shariff says. “The specific concepts of ‘exaptation’ and ‘ritualization’ that we discuss are quite common when discussing the evolution of non-human animals.” For example, some male birds bring a tiny morsel of food to a female bird as part of an elaborate courtship display. In that case, something that might once have been biologically relevant—sharing food with another bird—has evolved over time into a signal of his excellence as a potential mate. In the same way, Shariff says, facial expressions that started as part of the body’s response to a situation may have evolved into a social signal. 

Source: Association for Psychological Science [December 22, 2011]

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Was Darwin wrong about emotions?

Contrary to what many psychological scientists think, people do not all have the same set of biologically "basic" emotions, and those emotions are not automatically expressed on the faces of those around us, according to the author of a new article published in Current Directions in Psychological Science, a journal published by the Association for Psychological Science. This means a recent move to train security workers to recognize "basic" emotions from expressions might be misguided. 

"What I decided to do in this paper is remind readers of the evidence that runs contrary to the view that certain emotions are biologically basic, so that people scowl only when they're angry or pout only when they're sad," says Lisa Feldman Barrett of Northeastern University, the author of the new paper. 

The commonly-held belief is that certain facial muscle movements (called expressions) evolved to express certain mental states and prepare the body to react in stereotyped ways to certain situations. For example, widening the eyes when you're scared might help you take in more information about the scene, while also signaling to the people around you that something dangerous is happening. 

But Barrett (along with a minority of other scientists) thinks that expressions are not inborn emotional signals that are automatically expressed on the face. "When do you ever see somebody pout in sadness? When it's a symbol," she says. "Like in cartoons or very bad movies." People pout when they want to look sad, not necessarily when they actually feel sad, she says. 

Some scientists have proposed that emotions regulate your physical response to a situation, but there's no evidence, for example, that a certain emotion usually produces the same physical changes each time it is experienced, Barrett says. "There's tremendous variety in what people do and what their bodies and faces do in anger or sadness or in fear," she says. People do a lot of things when they're angry. Sometimes they yell; sometimes they smile. 

"Textbooks in introductory psychology says that there are about seven, plus or minus two, biologically basic emotions that have a designated expression that can be recognized by everybody in the world, and the evidence I review in this paper just doesn't support that view," she says. Instead of stating that all emotions fall into a few categories, and everyone expresses them the same way, Barrett says, psychologists should work on understanding how people vary in expressing their emotions. 

This debate isn't purely academic. It has consequences for how clinicians are trained and also for the security industry. In recent years there's been an explosion of training programs that are meant to help security officers of all kinds identify people who are up to something nefarious. But this training might be misguided, Barrett says. "There's a lot of evidence that there is no signature for fear or anger or sadness that you could detect in another person. If you want to improve your accuracy in reading emotion in another person, you have to also take the context into account." 

Incidentally, the theory that emotional expressions evolved for specific functions is normally attributed to Charles Darwin, in his book The Expression of the Emotions in Man and Animals. But Darwin didn't write that emotional expressions are functional. "If you're going to cite Darwin as evidence that you're right, you'd better cite him correctly," Barrett says. Darwin thought that emotional expressions – smiles, frowns, and so on –were akin to the vestigial tailbone – and occurred even though they are of no use. 

Source: Association for Psychological Science [December 13, 2011]

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All it takes is a smile (for some guys)

Does she or doesn't she . . .? Sexual cues are ambiguous, and confounding. We—especially men—often read them wrong. A new study hypothesizes that the men who get it wrong might be the ones that evolution has favored. "There are tons of studies showing that men think women are interested when they're not," says Williams College psychologist Carin Perilloux, who conducted the research with Judith A. Easton and David M. Buss of University of Texas at Austin. "Ours is the first to systematically examine individual differences." The findings will appear in an upcoming issue of Psychological Science, a journal published by the Association for Psychological Science. 

The research involved 96 male 103 female undergraduates, who were put through a "speed-meeting" exercise—talking for three minutes to each of five potential opposite-sex mates. Before the conversations, the participants rated themselves on their own attractiveness and were assessed for the level of their desire for a short-term sexual encounter. After each "meeting," they rated the partner on a number of measures, including physical attractiveness and sexual interest in the participant. The model had the advantage of testing the participants in multiple interactions. 

The results: Men looking for a quick hookup were more likely to overestimate the women's desire for them. Men who thought they were hot also thought the women were hot for them—but men who were actually attractive, by the women's ratings, did not make this mistake. The more attractive the woman was to the man, the more likely he was to overestimate her interest. And women tended to underestimate men's desire. 

A hopeless mess? Evolutionarily speaking, maybe not, say the psychologists. Over millennia, these errors may in fact have enhanced men's reproductive success. 

"There are two ways you can make an error as a man," says Perilloux. "Either you think, 'Oh, wow, that woman's really interested in me'—and it turns out she's not. There's some cost to that," such as embarrassment or a blow to your reputation. The other error: "She's interested, and he totally misses out. He misses out on a mating opportunity. That's a huge cost in terms of reproductive success." The researchers theorize that the kind of guy who went for it, even at the risk of being rebuffed, scored more often—and passed on his overperceiving tendency to his genetic heirs. The casual sex seekers "face slightly different adaptive problems," says Perilloux. "They are limited mainly by the number of consenting sex partners—so overestimation is even more important." Only the actually attractive men probably had no need for misperception. 

The research contains some messages for daters of both sexes, says Perilloux: Women should know the risks and "be as communicative and clear as possible." Men: "Know that the more attracted you are, the more likely you are to be wrong about her interest." Again, that may not be as bad as it sounds, she says—"if warning them will prevent heartache later on." 

Source: Association for Psychological Science [December 13, 2011]

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Starving orangutans might help to better understand obesity and eating disorders in humans

Rutgers Evolutionary Anthropologist Erin Vogel thinks new research published today in Biology Letters, a Journal of the Royal Society, examining how endangered Indonesian orangutans – considered a close relative to humans -- survive during times of extreme food scarcity might help scientists better understand eating disorders and obesity in humans. 

Endangered Indonesian orangutans survive during times of extreme food scarcity and starvation [Credit: Erin Vogel]

"There is such a large obesity epidemic today and yet we don't really understand the basis of the obesity condition or how these high-protein or low-protein diets work," said Vogel, whose research, Bornean orangutans on the brink of protein bankruptcy, represents the first time scientists have looked at how these long-haired, orange-colored apes -- that depend on low-protein fruit to survive -- endure protein cycling, or period bouts of protein deprivation. "I think studying the diets of some of our closest living relatives, the great apes; may help us understand issues with our own modern day diets," she said. 

According to Vogel, an assistant professor of anthropology in Department of Anthropology and Center for Human Evolutionary Studies, in the School of Arts and Sciences, the research shows that it is only during high periods of high caloric and protein intake that orangutans put on fat, a scientific fact that is sometimes ignored by those who believe that high protein, low carbohydrate diets are the best way to lose weight. She said it is only when caloric intake is restricted that orangutans use these fat reserves for energy and eventually dip into their protein (muscle) reserves – a condition that is seen with eating disorders like anorexia. 

Orangutans in particular are interesting to study, Vogel said, because they are the only documented species of non-human ape to store fat when food is abundant in the wild and use these fat reserves when preferred fruits become scarce, presumably something done by our early hominin ancestors. 

Vogel and her research team, analyzed samples collected over a five-year period to study the effects of protein recycling, which included examining urinary metabolites and nitrogen stable isotopes – compounds and byproducts in Orangutan urine. What they determined is that these primates are able to endure prolonged protein deficits without starving to death by consuming higher protein leaves and inner bark and obtaining energy from their stored body fat and even muscles for an extended period of time when low-protein fruit is unavailable. 

"We discovered through this research that the daily amount of protein the orangutans take in when fruit is not available is inadequate for humans and one-tenth of the intake of mountain gorillas. But it is sufficient to avert a severe protein deficit," said Vogel. The Bornean orangutan population has fallen drastically in the last 50 years in Indonesia to less than 55,000 and on the island of Sumatra to less than 5,000 due to a massive amount of illegal logging and further clearing of the land to develop palm oil plantations in their now impoverished rainforest habitat. Vogel says that although some palm oil companies argue that clearing partially logged areas of the rainforest for palm oil plantations is not detrimental to the existence of the orangutan because their natural habitat has already been taken away, this research on protein cycling indicates that even areas that have been partially stripped of trees are better for orangutan survival than no forest area at all. 

Source: Rutgers University [December 13, 2011]

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Why aren't we smarter already? Evolutionary limits on cognition

We put a lot of energy into improving our memory, intelligence, and attention. There are even drugs that make us sharper, such as Ritalin and caffeine. But maybe smarter isn’t really all that better. A new paper published in Current Directions in Psychological Science, a journal of the Association for Psychological Science, warns that there are limits on how smart humans can get, and any increases in thinking ability are likely to come with problems. 

The authors looked to evolution to understand about why humans are only as smart as we are and not any smarter. “A lot of people are interested in drugs that can enhance cognition in various ways,” says Thomas Hills of the University of Warwick, who cowrote the article with Ralph Hertwig of the University of Basel. “But it seems natural to ask, why aren’t we smarter already?” 

Tradeoffs are common in evolution. It might be nice to be eight feet tall, but most hearts couldn’t handle getting blood up that high. So most humans top out under six feet. Just as there are evolutionary tradeoffs for physical traits, Hills says, there are tradeoffs for intelligence. A baby’s brain size is thought to be limited by, among other things, the size of the mother’s pelvis; bigger brains could mean more deaths in childbirth, and the pelvis can’t change substantially without changing the way we stand and walk. 

Drugs like Ritalin and amphetamines help people pay better attention. But they often only help people with lower baseline abilities; people who don’t have trouble paying attention in the first place can actually perform worse when they take attention-enhancing drugs. That suggests there is some kind of upper limit to how much people can or should pay attention. “This makes sense if you think about a focused task like driving,” Hills says, “where you have to pay attention, but to the right things—which may be changing all the time. If your attention is focused on a shiny billboard or changing the channel on the radio, you’re going to have problems.” 

It may seem like a good thing to have a better memory, but people with excessively vivid memories have a difficult life. “Memory is a double-edged sword,” Hills says. In post-traumatic stress disorder, for example, a person can’t stop remembering some awful episode. “If something bad happens, you want to be able to forget it, to move on.” 

Even increasing general intelligence can cause problems. Hills and Hertwig cite a study of Ashkenazi Jews, who have an average IQ much higher than the general European population. This is apparently because of evolutionary selection for intelligence in the last 2,000 years. But, at the same time, Ashkenazi Jews have been plagued by inherited diseases like Tay-Sachs disease that affect the nervous system. It may be that the increase in brain power has caused an increase in disease. 

Given all of these tradeoffs that emerge when you make people better at thinking, Hills says, it’s unlikely that there will ever be a supermind. “If you have a specific task that requires more memory or more speed or more accuracy or whatever, then you could potentially take an enhancer that increases your capacity for that task,” he says. “But it would be wrong to think that this is going to improve your abilities all across the board.” 

Source: Association for Psychological Science [December 06, 2011]

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