Big Brain Power Demands Fire Power!

Image: Madeleine Ball/Flickr
"Mmm yummy, tasty, juicy...puh puh puh!"

(Wired.com, 23, Oct 2012) - Eating a raw food diet is a recipe for disaster if you’re trying to boost your species’ brainpower. That’s because humans would have to spend more than 9 hours a day eating to get enough energy from unprocessed raw food alone to support our large brains, according to a new study that calculates the energetic costs of growing a bigger brain or body in primates. But our ancestors managed to get enough energy to grow brains that have three times as many neurons as those in apes such as gorillas, chimpanzees, and orangutans. How did they do it? They got cooking, according to a study published online today in the Proceedings of the National Academy of Sciences.

“If you eat only raw food, there are not enough hours in the day to get enough calories to build such a large brain,” says Suzana Herculano-Houzel, a neuroscientist at the Federal University of Rio de Janeiro in Brazil who is co-author of the report. “We can afford more neurons, thanks to cooking.”

Humans have more brain neurons than any other primate — about 86 billion, on average, compared with about 33 billion neurons in gorillas and 28 billion in chimpanzees. While these extra neurons endow us with many benefits, they come at a price — our brains consume 20 percent of our body’s energy when resting, compared with 9 percent in other primates. So a long-standing riddle has been where did our ancestors get that extra energy to expand their minds as they evolved from animals with brains and bodies the size of chimpanzees?

One answer came in the late 1990s when Harvard University primatologist Richard Wrangham proposed that the brain began to expand rapidly 1.6 million to 1.8 million years ago in our ancestor, Homo erectus, because this early human learned how to roast meat and tuberous root vegetables over a fire. Cooking, Wrangham argued, effectively predigested the food, making it easier and more efficient for our guts to absorb calories more rapidly. Since then, he and his colleagues have shown in lab studies of rodents and pythons that these animals grow up bigger and faster when they eat cooked meat instead of raw meat — and that it takes less energy to digest cooked meat than raw meat.

In a new test of this cooking hypothesis, Herculano-Houzel and her graduate student, Karina Fonseca-Azevedo, now a neuroscientist at the National Institute of Translational Neuroscience in São Paulo, Brazil, decided to see if a diet of raw food inherently put limits on how large a primate’s brain or body could grow. First, they counted the number of neurons in the brains of 13 species of primates (and more than 30 species of mammals). The researchers found two things: one, that brain size is directly linked to the number of neurons in a brain; and two, that that the number of neurons is directly correlated to the amount of energy (or calories) needed to feed a brain.

After adjusting for body mass, they calculated how many hours per day it would take for various primates to eat enough calories of raw food to fuel their brains. They found that it would take 8.8 hours for gorillas; 7.8 hours for orangutans; 7.3 hours for chimps; and 9.3 hours for our species, H. sapiens.

These numbers show that there is an upper limit on how much energy primates can get from an unprocessed raw diet, Herculano-Houzel says. An ape’s diet in the wild differs from a modern “raw food diet,” in which humans get sufficient calories from processing raw food in blenders and adding protein and other nutrients. In the wild, other apes can’t evolve bigger brains unless they reduce their body sizes because they can’t get past the limit of how many calories they can consume in 7 hours to 8 hours of feeding per day. But humans, she says, got around that limit by cooking. “The reason we have more neurons than any other animal alive is that cooking allowed this qualitative change — this step increase in brain size,” she says. “By cooking, we managed to circumvent the limitation of how much we can eat in a day.”

This study shows “that an ape could not achieve a brain as big as in recent humans while maintaining a typical ape diet,” Wrangham says.

Paleoanthropologist Robert Martin of The Field Museum in Chicago, Illinois, agrees that the new paper does “provide the first evidence that metabolic limitations” from a raw food diet impose a limit on how big a primate’s brain — or body — can grow. “This could account for small brain sizes of great apes despite their large body sizes.” But “the jury is still out” on whether cooking was responsible for the first dramatic burst of brain growth in our lineage, in H. erectus, Martin says, or whether our ancestors began cooking over a fire later, when the brain went through a second major growth spurt about 600,000 years ago. Hearths show up in the archaeological record 800,000 years ago and the regular use of fire for cooking doesn’t become widespread until more recently.

But to Herculano-Houzel’s mind, our brains would still be the size of an ape’s if H. erectus hadn’t played with fire: “Gorillas are stuck with this limitation of how much they can eat in a day; orangutans are stuck there; H. erectus would be stuck there if they had not invented cooking,” she says. “The more I think about it, the more I bow to my kitchen. It’s the reason we are here.”

NOC, the white whale that tried to sound like a humanz

RE: Audio file.  I bet his has names for all his toes

(Discover Magazine.com, 22, Oct 2012) - Listen to this recording. It sounds like a drunkard playing a kazoo, but it’s actually the call of a beluga (a white whale) called NOC. Belugas don’t normally sound like that; instead, NOC’s handlers think that his bizarre sounds were an attempt at mimicking the sounds of human speech.

The idea isn’t far-fetched. Belugas are so vocal that they’re often called “sea canaries”. William Schevill and Barbara Lawrence – the first scientists to study beluga sounds in the wild – wrote that the calls would occasionally “suggest a crowd of children shouting in the distance”. Ever since, there have been many anecdotes that these animals could mimic human voices, including claims that Lagosi, a male beluga at Vancouver Aquarium, could speak his own name. But until now, no one had done the key experiment.  No one had recorded a beluga doing its alleged human impression, and analysed the call’s acoustic features.

NOC provided the right opportunity. He was one of three belugas that arrived at the National Marine Mammal Foundation (NMMF) in San Diego in August 1977, after originally being captured by Inuit hunters in Canada. Being the smallest of the trio, NOC was cheekily named after “noseum”, the tiny gnats that plague the hunters during the Canadian summer.

In May 1984, seven years after NOC’s arrival at San Diego, the staff at the NMMF started making noises that resembled speech-like sounds. At first, no one could work out where the noises were coming from. They sounded “as if two people were conversing in the distance just out of range for our understanding,” writes Sam Ridgway.

The mystery was solved later that year, through a lucky accident. A group of divers were training outside NOC’s enclosure, when one of them surfaced and asked “Who told me to get out?”

It was NOC.

After that incident, the trainers watched him more closely and confirmed that he was the source of their mysterious noises. He did so spontaneously, without any training. And he made the calls when alone or when his human handlers were around, and never when socialising with the other two whales in his tank.

Ridgway’s team recorded NOC’s calls, and found that their acoustic features were very unlike typical whale sounds, but not unlike those of human speech. The rhythm was comparable, with vocal bursts that lasted for around three seconds and gaps of less than 0.5 seconds. NOC’s calls had a fundamental frequency of 200 to 300 Hz (the octave around middle C), which is similar to the range of human speech, and much lower than a whale’s usual sounds.

After many rounds of recording, Ridgway’s team started training NOC to make the speech-like sounds on cue, so they could better study how he did it. Whales produce sounds by sending air from their nasal tract past their phonic lips – a pair of vibrating muscular folds that act like our voice box. From there, the air enters two pouches called the vestibular sacs. NOC mimicked human noises by increasing the pressure in his nasal tract, finely controlling the vibrations of his phonic lips, and greatly over-inflating his vestibular sacs, to hit those lower registers.

Stan Kuczaj, who studies sea mammal behaviour at the University of Southern Mississippi, is convinced. “The beluga did seem to be mimicking human speech, and did so quite successfully,” he says. “Belugas are known to have excellent acoustic mimicry skills.”

Justin Gregg from the Dolphin Communication Project, says, “Listening to the recording, it does not sound exactly like human speech—I have no idea what the whale is “saying”—but [Ridgway’s team] have certainly made the case that the whale was trying very hard to produce human language sounds.”

“We do not claim that our whale was a good mimic compared to such well-known mimics as parrots or mynah birds,” writes Ridgway. But he maintains that the calls he recorded are a good example of vocal learning – where animals learn to make noises based on hearing others around them. In this case, it’s likely that NOC picked up the pitch and rhythm of human speech after spending years in close contact with his handlers.

Why? Kuczak says, “I don’t think the whale was trying to learn human speech in order to communicate with humans.” Instead, he suggests that NOC was simply interested in these odd sounds in his environment, and tried to reproduce them.

Gregg adds that belugas, like dolphins, are very social animals, and the ability to learn and mimic new calls might help them to address other individuals. They also have very sophisticated echolocation, and can subtly alter their ultrasonic clicks to scan their environment. “They already have an amazing ability to alter parameters of their vocal tract, which should make it all the more easy to replicate human speech sounds,” says Gregg.

NOC’s attempts at human-like sounds continued for four years. As he grew up, he stopped, but he carried on being talkative, with a regular portfolio of “squawks, rasps, yelps or barks”.

Five years ago, NOC stopped calling altogether. He finally passed away after 30 years at the NMMF. Through Ridgway’s recordings, his voice echoes on.

Journal article: http://www.cell.com/current-biology/abstract/S0960-9822(12)01009-3

Books Change How a Child’s Brain Grows (Zombie community pleased)

Image: Peter Dedina/Flickr
"I loveses you book, I'll never replace you in the
near future with an electronic alternative"

(Wired.com, 18, Oct 2012) - Books and educational toys can make a child smarter, but they also influence how the brain grows, according to new research presented here on Sunday at the annual meeting of the Society for Neuroscience. The findings point to a “sensitive period” early in life during which the developing brain is strongly influenced by environmental factors.

Studies comparing identical and nonidentical twins show that genes play an important role in the development of the cerebral cortex, the thin, folded structure that supports higher mental functions. But less is known about how early life experiences influence how the cortex grows.

To investigate, neuroscientist Martha Farah of the University of Pennsylvania and her colleagues recruited 64 children from a low-income background and followed them from birth through to late adolescence. They visited the children’s homes at 4 and 8 years of age to evaluate their environment, noting factors such as the number of books and educational toys in their houses, and how much warmth and support they received from their parents.

More than 10 years after the second home visit, the researchers used MRI to obtain detailed images of the participants’ brains. They found that the level of mental stimulation a child receives in the home at age 4 predicted the thickness of two regions of the cortex in late adolescence, such that more stimulation was associated with a thinner cortex. One region, the lateral inferior temporal gyrus, is involved in complex visual skills such as word recognition.

Home environment at age 8 had a smaller impact on development of these brain regions, whereas other factors, such as the mother’s intelligence and the degree and quality of her care, had no such effect.

Previous work has shown that adverse experiences, such as childhood neglect, abuse, and poverty, can stunt the growth of the brain. The new findings highlight the sensitivity of the growing brain to environmental factors, Farah says, and provide strong evidence that subtle variations in early life experience can affect the brain throughout life.

As the brain develops, it produces more synapses, or neuronal connections, than are needed, she explains. Underused connections are later eliminated, and this elimination process, called synaptic pruning, is highly dependent upon experience. The findings suggest that mental stimulation in early life increases the extent to which synaptic pruning occurs in the lateral temporal lobe. Synaptic pruning reduces the volume of tissue in the cortex. This makes the cortex thinner, but it also makes information processing more efficient.

“This is a first look at how nurture influences brain structure later in life,” Farah reported at the meeting. “As with all observational studies, we can’t really speak about causality, but it seems likely that cognitive stimulation experienced early in life led to changes in cortical thickness.”

She adds, however, that the research is still in its infancy, and that more work is needed to gain a better understanding of exactly how early life experiences impact brain structure and function.

The findings add to the growing body of evidence that early life is a period of “extreme vulnerability,” says psychiatrist Jay Giedd, head of the brain imaging unit in the Child Psychiatry Branch at the National Institute of Mental Health in Bethesda, Maryland. But early life, he says, also offers a window of opportunity during which the effects of adversity can be offset. Parents can help young children develop their cognitive skills by providing a stimulating environment.

"Sponging" dolphins pass fishing trick from mother to daughter

*Muffled* Can someone CLICK! get this CLICK!
off my CLICKIN! nose!?

(Reuters.con, 15, Oct 2012) - A small population of dolphins in Western Australia state not only use sponges to help catch fish but the rare hunting technique has been passed from mother to daughter for generations, Australian researchers said.

Sightings of dolphins carrying sponges on their snouts to protect their sensitive noses while dislodging fish and crustaceans from the rocky ocean floor has been recorded since the 1980s.

But researchers at the University of New South Wales added a new dimension to their research by using computer modeling of behavior (Social Network Analysis) and genetics to estimate how long the technique, which they call "sponging", has gone on.

"What's unique about the sponging behavior is that only about five percent of dolphins use the sponges as a tool, and it's only one maternal line," said Anna Kopps at the University of New South Wales Evolution Ecologist Research Centre.

"What's new about this study now is we've got the time perspective," she told Reuters.

Scientists believe one single female started sponging in Shark Bay, Western Australia, and all her descendants in that area learned the behavior from their mothers.

Knowing this, and that the sponging was done 30 years ago, computer modeling allowed them to study the spread of the behavior over the past three decades -- and then reverse the process using genetics and behavior to figure out when it might have begun.

Ultimately, they estimated that sponging has been going on for some 180 years, or roughly eight generations of dolphins.

"It's interesting that the behavior doesn't spread to the entire population and it doesn't go extinct either," said Kopps.

Dolphin offspring are dependent on their mothers for about four years, giving them ample time to observe and learn survival techniques. The maximum lifespan of a dolphin is about 40 years.

"We don't know if it's teaching or other forms of learning," Kopps said.

While male dolphins also learn sponging from their mothers, the study found they don't pass the technique on.

"Some males use it but not many and it will be a dead end because they don't learn from the dads," Kopps said.

Neanderthals ... They're Just Like Us?

Photograph by Joe McNally, National Geographic
 "Come at me bro"

(National Geographic.com, 12, Oct 2012) - Well, not exactly. But new discoveries have had a surprisingly humanizing effect.

The Neanderthals are both the most familiar and the least understood of all our fossil kin.

For decades after the initial discovery of their bones in a cave in Germany in 1856 Homo neanderthalensis was viewed as a hairy brute who stumbled around Ice Age Eurasia on bent knees, eventually to be replaced by elegant, upright Cro-Magnon, the true ancestor of modern Europeans.

Science has long since killed off the notion of that witless caveman, but Neanderthals have still been regarded as quintessential losers—a large-brained, well-adapted species of human that went extinct nevertheless, yielding the Eurasian continent to anatomically modern humans, who began to migrate out of Africa some 60,000 years ago.

Lately, the relationship between Neanderthals and modern humans has gotten spicier.

According to a new study that analysed traces of Neanderthal DNA in present-day humans, Neanderthals may have been interbreeding with some of the ancestors of modern Eurasians as recently as 37,000 years ago. And another recent study found that Asian and South American people possess an even greater percentage of Neanderthal genes.

"These are complexities in the out-of-Africa story that certainly I would not have anticipated two or three years ago," said Chris Stringer, a paleoanthropologist at the Natural History Museum in London and author of Lone Survivors: How We Came to Be the Only Humans on Earth.

In their original incarnation, Neanderthals were viewed as the primitive, backward cave dwellers of Eurasia, far less complex than the sophisticated Homo sapiens who used language and developed sophisticated art as they migrated out of Africa and conquered the world.

But new studies are making it much harder to draw a clean line between us and them.

"It's increasingly difficult to point to any one thing that Neanderthals did and Homo sapiens didn't do and vice versa," said John Shea, an archaeologist at Stony Brook University in New York.

"These Ice Age people, both Neanderthals and Homo sapiens, survived, thrived, and increased their numbers under conditions that would probably kill people nowadays, even ones that are equipped with modern survival technology."

The draft sequence of the Neanderthal genome, published in the journal Science in 2010, provided the first compelling genetic evidence that Neanderthals and H. sapiens had more in common than just an ancestor in Africa hundreds of thousands of years ago.

The researchers, under the direction of Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology, found that 2.5 percent of the genome of an average human living outside Africa today is made up of Neanderthal DNA. The average modern African has none.

This suggested that some interbreeding had taken place between the two kinds of human, probably in the Middle East, where the early modern humans migrating out of Africa would have encountered Neanderthals already living there.

The even larger percentage of Neanderthal DNA found in Asians and South Americans, announced in Science in August, could indicate additional interbreeding in Asia long ago, or could mean that the percentage of Neanderthal DNA in Europeans was diluted by later encounters.

Not everyone is convinced that interbreeding was responsible for similarities in the Neanderthal and H. sapiens genomes. "The similarities they're seeing may be ancient," Shea noted.

Another recent study, published in the journal Proceedings of the National Academy of Sciences in August, calculated that the shared DNA could have come from an earlier, common ancestor of Neanderthals and H. sapiens—no hanky-panky necessary.

A new study by Pääbo's team, published last week in PLOS Genetics, also considered the possibility that the presence of Neanderthal DNA in people living outside Africa today could be traced far back, to the common ancestor of both Neanderthals and modern humans in Africa.

Perhaps the early modern humans who left Africa 60,000 years ago were already genetically more similar to the Neanderthals—who had left hundreds of thousands of years before—than were the modern human populations that stayed behind in Africa. In that case, no interbreeding would have needed to occur to account for the trace of Neanderthal DNA in non-Africans today.

To test the two hypotheses, Pääbo's group analyzed the lengths of segments of Neanderthal DNA in modern Europeans to determine when Neanderthal genes may have mixed with those of modern humans. The date they came up with for the gene flow was 37,000 to 86,000 years ago, and most likely 47,000 to 65,000 years ago.

This date strongly suggests there was indeed interbreeding between "us and them," when H. sapiens was moving into the Middle East from Africa and would have encountered populations of Neanderthals already settled there.

"This [interbreeding] could have been a really powerful mechanism for humans to adapt as they moved into Eurasia," said Sriram Sankararaman, a statistical geneticist at Harvard Medical School and the lead author of the PLOS Genetics study.

Another group, publishing last year in Science, for example, determined that modern humans gained from Neanderthals a family of genes that helps the immune system fight off viruses. Breeding with the locals could have unwittingly given H. sapiens a survival advantage in a new land.

"[Neanderthals] are not just some extinct group of related hominids," Pääbo said. "They are partially ancestors to people who live today."

Take any two unrelated humans today, Pääbo noted, and they'll differ in millions of places in their genetic code. But the Neanderthal genome varies on average from that of H. sapiens in only about a hundred thousand positions. Pääbo and his colleagues are now trying to figure out the consequences of those differences.

Regardless of the similarities to our DNA, how "human" were Neanderthals in their sensibilities?

Last month a study led by the Gibraltar Museum and published in PLOS ONE documented a multitude of fossil remains of bird wings, particularly from big black raptors, at Neanderthal sites in southern Europe. The team suggested that Neanderthals could have been plucking feathers from the wings for personal use or even for ritual ornaments.

"We have other evidence for Neanderthals preferring mineral pigments that are dark, blackish color," Stony Brook's Shea said. "There may be something for them with the color black just as there seems to be something for us with the colour red."

Sophisticated art, however, still appears to remain in the realm of H. sapiens.

The ancestors of modern humans left behind images of animals and other objects in caves around the world, most famously at Lascaux cave and Chauvet Cave (pictures) in southern France. Paintings in the latter cave could be as ancient as 37,000 years old. (See a prehistoric time line.)

Images found in a cave called El Castillo on the Spanish coast were recently dated at more than 40,800 years old: a time before Neanderthals disappeared, raising the tantalizing possibility that they were indeed the artists. However, "it hasn't been demonstrated that Neanderthals produced any of that cave art," the Natural History Museum's Stringer said.

The simpler answer is that H. sapiens, who had also reached Europe by that time and are known to have produced later but similar art, were responsible.

Neanderthals, though, have proven advanced in other ways.

They used pigments and may have made jewellery; some made complex tools. "We know they buried their dead," Stringer said. In 2010, researchers from the Smithsonian Institution even found evidence that the Neanderthal diet included a diverse mixture of plants, and that they cooked some of the grains.

"Cooking something like oatmeal is not what we would have imagined," said John Hawks, paleoanthropologist at the University of Wisconsin-Madison. With no pots, Neanderthals may have cooked inside leaves, Hawks suggested. "That starts to sound like cuisine."

"Neanderthals have gone from being different from us to being like us," Hawks noted. "They're looking like [Homo sapiens] hunter-gatherers look."

But while modern humans continued to develop cultural complexity and spread across the globe, the Neanderthals vanished. Why remains a mystery.

Are Humans Monogamous or Polygamous?

Photo by Georges Gobet/AFP/Getty Images.
"My eyes are up here pal" 

(Slate.com, 9, Oct 2012) - Archaeologists, anthropologists, and biologists agree: It’s complicated.

What makes us different from all the other animals? Is it our swollen brains, our idle hands, or perhaps our limber thumbs? In 2011, a research team reviewed the quirks of human DNA and came across another oddly shaped appendage that makes us who we are: I mean, of course, man's smooth and spineless member. The penises of lots of mammals are endowed with "horny papillae," hardened bumps or spikes that sometimes look like rows of studs on a fancy condom. These papillae enhance sensation, or so it has been claimed, and shorten a mating male's delay to climax. Since humans lost their phallic bumps several million years ago, it could be that we evolved to take it slow. And it could also be the case that longer-lasting sex produced more intimate relationships.

So (one might argue that) the shedding of our penis spines gave rise to love and marriage, and (one could also say that) our tendency to mate in pairs pushed aside the need for macho competition, which in turn gave us the chance to live together in large and peaceful groups. Life in groups has surely had its perks, not least of which is that it led to bigger brains and a faculty for language, and perhaps a bunch of traits that served to civilize and tame us. And so we've gone from horny papillae to faithful partners—from polygamy to monogamous humanity.

I like this story well enough, but it may or may not be true. In fact, not all penis spines in nature serve to quicken sex—orangutans have fancy ones but waste a quarter of an hour in the act—so we don't know what to make of our papillae or the lack thereof. That won't stop anyone from wondering.

Since we like to think that how we mate defines us, the sex lives of ancient hominids have for many years been examined in computer simulations, by measuring the circumferences of ancient bones, and by applying the rules of evolution and economics. But to understand the contentious field of paleo-sexology, one must first address the question of how we mate today, and how we’ve mated in the recent past.

According to anthropologists, only 1 in 6 societies enforces monogamy as a rule. There's evidence of one-man-one-woman institutions as far back as Hammurabi's Code; it seems the practice was further codified in ancient Greece and Rome. But even then, the human commitment to fidelity had its limits: Formal concubines were frowned upon, but slaves of either sex were fair game for extramarital affairs. The historian Walter Scheidel describes this Greco-Roman practice as polygynous monogamy—a kind of halfsy moral stance on promiscuity. Today's Judeo-Christian culture has not shed this propensity to cheat. (If there weren't any hanky-panky, we wouldn't need the seventh commandment.)

In The Myth of Monogamy, evolutionary psychologists David P. Barash and Judith Eve Lipton say we're not the only pair-bonding species that likes to sleep around. Even among the animals that have long been known as faithful types—nesting birds, etc.—not too many stay exclusive. Most dally. "There are a few species that are monogamous," says Barash. "The fat-tailed dwarf lemur. The Malagasy giant jumping rat. You've got to look in the nooks and crannies to find them, though." Like so many other animals, human beings aren't really that monogamous. Better to say, we're monogamish.

That –ish has caused no end of trouble, for lovers and for scientists. Efforts to define our sexual behavior often run afoul of humans’ in-between-ness. Take one common proxy measure of how a primate species copulates: testis size. A male that's forced to share its partners might do well to make each ejaculation count by firing off as many sperm as possible. Chimpanzees mate rather freely and show a high degree of male-male competition. They also have giant balls, for blowing away their rivals'. Gorillas, on the other hand, have their sexual dynamics more worked out: The alpha male has all the sex; the other males are screwed. Since there's less chance of going head-to-head on ejaculations, tesis size isn't so important. Gorilla balls are pretty small. And what about a man's testes? They're not so big and not so little. They're just eh.

Male gorillas may not one-up each other with their testes, but they do rely on other traits to get and keep their harems. That's why male gorillas are so huge and fearsome: so they can fight off other males for social dominance. Within a species, the difference between the male and female body type yields another proxy for mating habits: The bigger the gap in body size, the more competitive the males, and the greater the inclination toward polygynous arrangements. So how does the split between human men and women compare to that of other primates? We're sort of in the middle.

Seeing as we're neither one thing nor the other, scientists have been left to speculate on how our ancestors might have done their thing. Were they like gorillas, where most males suffered while one dude enjoyed the chance to spread his seed? Or more like chimpanzees—sleeping around, with males competing for multiple partners? Or is there another possibility, like the one championed by Christopher Ryan and Cacilda Jethá in their best-selling and soundly criticized paean to free love, Sex at Dawn? According to that book's authors, our ancestors did as bonobos do: They had rampant sex without much bickering.

Such discussions tend to dead-end quickly, though, since we just don't know for sure. Our most recent relatives in common with these other primates lived about 6 million years ago. (I suppose if bonobos could be anthropologists, one of them might write a book on whether bonobo sexuality evolved from something humanlike.) "What this really is," says Barash, "is a Rorschach test for the people asking the question."

We do have data on human mating trends, but the record tends to be a little spotty. In 2010, a team in Montreal completed its analysis of breeding ratios for Homo sapiens based on a careful study of DNA. By measuring diversity in the human chromosomes, the researchers tried to figure out what proportion of the breeding pool has been composed of females. They found a ratio of slightly more than one-to-one, meaning that there were at least 11 ladies for every minyan of procreating men. But the math they used turned out to be a little wonky, and after making some corrections, they revised the numbers up a bit toward a ratio of 2. These estimates, they wrote, are still within the range you'd find for societies described as "monogamous or serially monogamous, although they also overlap with those characterizing polygyny." Once again—we're monogamish.

At what point in hominid evolution did this in-between behavior appear? Paleontologist Owen Lovejoy published fossil specimens in 2009 from Ardipithecus ramidus, which lived 4.4 million years ago. He used the newly described species as evidence for the hominids' great transition to (mostly) one-on-one relationships. Ardi walked on two legs, which freed its hands for carrying food, and males that carried food, he says, were thus enabled to take that food to females. They'd evolved a way to pitch woo and bring home the bacon. By this stage in evolution, sexual dimorphism had been diminished, too, and so had other signs of male-on-male competition. Taken together, Lovejoy wrote in Science, these data points suggest "a major shift in life-history strategy [that] transformed the social structure of early hominids." Males and females had started pairing off, and dads learned how to support their families.

A computation-minded researcher at the University of Tennessee, Sergey Gavrilets, finished up a study in May of how that transition might have followed the laws of natural selection. It's not an easy puzzle. Gavrilets explains that a polygynous mating scheme can lead to a "vicious circle" where males waste their time and energy in fighting over females. The group might be better off if everyone split off into happy, hetero-pairs and worked on caring for their babies. But once you've started wars for sex, there's an evolutionary push to keep them going. So Gavrilets set up a computer model to see if any movement toward monogamy might conform to what we know of evolution. He found that a shift in female preference for mates that offer food and child care could have made it happen. (Low-ranked males might also favour relationships with partners that didn't cheat.)

Gavrilets says he needs to check his model against a few more theories of how human-style partnerships evolved—including one that involves the invention of cooked food. But he's made the case, at least, that biology could lead to modern love, without any help from law or custom. "Culture came much later," he told a reporter in the spring, "and only augmented things that were already in place."

That's one idea, but the study of monogamy takes all kinds. Others have been more interested in the culture and the customs. In January, a scholar named Joe Henrich published with his colleagues an account of how and why the one-partner system might have spread as a social norm. The paper points out that marriage customs are not the same as mating strategies. (They are related, though: We tend to internalize the rules of the society we live in, so "doing right" becomes its own reward.) The authors argue that when a society gets big enough and sufficiently complex, it's advantageous for its culture to promote monogamy, or at least monogamishness.

Why? Because polygamy causes problems. Henrich, et al., review a large amount of evidence to support the claim that the multiwife approach leaves lots of men unmarried and so inclined to act in risky, angry ways. These bachelors are a menace: They increase the rates of crime and conflict, and lower productivity. In China, for example, a preference for male babies skewed the gender ratio quite dramatically from 1988 to 2004. In that time, the number of unmarried men nearly doubled, and so did crime. In India, murder rates track with male-to-female ratios across the country's states. Using these and other data, the authors argue that a culture of monogamy would tend to grow and thrive. It would be the fittest in its niche.

Of course it's also possible that high rates of conflict lead to cases of polygamy. Walter Scheidel points out that the ancient ban on multimarriage was suspended near the end of the Peloponnesian War, with so many soldiers dead that potential husbands were in short supply. Which raises the tricky question of how monogamy relates to war: Some have argued that pair-bonding leads to larger, stronger armies and more battle-ready people. Henrich, et al., suggest the opposite, that men with wives are less inclined to go to war, which weakens despots and promotes democracy.

The answer may be something in the middle, as it often is when it comes to the science of monogamy. Some cultures have made the practice into law and others haven't. Even our human physiology seems undecided on the issue. At every level of analysis, it's hard to say exactly what we are or how we live. We're faithful and we're not. We're lovers and we're cheaters.

Do Animals Get Depressed?

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(National Geographic.com, 4, Oct 2012) - Primates, rodents may show signs of sadness, study suggests.

Learning more about depression in animals could one day benefit humans, say scientists who believe that mammals share the same basic wiring in their brain for emotions as humans do. (Although not every scientist agrees with that premise.)

In the October 5 issue of Science, Assistant Professor of Neuroscience Olivier Berton and his colleagues at the University of Pennsylvania reviewed recent studies of rodents, primates, and fish who lacked interest in their environment and their fellow animals.

We spoke with Berton about what we do—and don't—know about animal depression.

Do animals get depressed?

Depression is diagnosed in humans based on a list of symptoms that are all very subjective. Common core symptoms include feelings of guilt, thoughts of death, and loss of pleasure. Because animals can't communicate even if they have these kinds of experiences, strictly the answer is: We can't say.

What signs may indicate if an animal is depressed?

There are certain aspects of the disease that may be measured in animals. One of the core symptoms of depression is anhedonia, the decrease and loss of interest in pleasurable activities. We measure interest in food that animals like a lot or in motivation for sexual activity. We also measure how they are interacting socially with other animals in the group, and changes in sleep patterns and daytime activities. Another behavior that has been used frequently to measure animal depression is whether they readily give up when exposed to a stressful situation.

What animals seem to exhibit signs of depression?

Definitely the most convincing observations derive from nonhuman primates. Based on behavioral observation, trained observers can say a monkey looks depressed. Because their emotional behaviors are similar to that of humans, just by looking at their facial expressions or the way their gaze is directed, we can get an indication of whether an animal may be experiencing sadness.

Can you really study animals in this environment?

One problem is that many lab studies in primates and rodents are conducted in captive animals that are raised in relatively impoverished conditions compared to their natural habitat. This can cause depression-like changes. Currently there is not a lot of data available that compares animal emotional behaviors in the wild versus in laboratory setting.

How would animals deal with depression in nature?

I don't know. There are very few systematic studies of this kind. It is possible that behavioral disorders in animals in the wild may impair their chances of survival. Maybe there is a point where they cannot deal and are more easily preyed upon.

Could domestic animals be depressed?

Veterinarians frequently give antidepressants to dogs to treat their behavioral disorders. For example, if an owner leaves the house and the dogs experience stress related to being separated, they may develop abnormal behaviors such as scratching themselves until they bleed or eating the door. These are thought to represent canine versions of psychiatric disorders. Although human treatments seem to work in dogs, large-scale studies are lacking.

Human brains grow bigger in the womb than chimpanzee's

(New Scientist.com, 25, Sept 2012) - Chimps may be similar to us in many ways but they can't compete when it comes to brain size. Now for the first time we can see when the differences emerge by tracking the brain development of unborn chimps.

As seen in this video, Tomoko Sakai and colleagues from Kyoto University in Japan subjected a pregnant chimp to a 3D ultrasound to gather images of the fetus between 14 and 34 weeks of development. The volume of its growing brain was then compared to that of an unborn human.

The team found that brain size increases in both chimps and humans until about 22 weeks, but after then only the growth of human brains continues to accelerate. This suggests that as the brain of modern humans rapidly evolved, differences between the two species emerged before birth as well as afterwards.

The researchers now plan to examine how different parts of the brain develop in the womb, particularly the forebrain, which is responsible for decision-making, self-awareness and creativity.

Busy Days at Living Links (Edinburgh Zoo)

(Living Links.org, 3, Oct 2012) - Over the past 2 weeks the Living Links team has had some busy days with visitors.

On Sunday the 23rd of September we had the St Andrews University PsychSoc visit Budongo and Living Links. They received an intro talk from Prof Andy Whiten and had guided tours from the Budongo keepers and Living Links research staff. They even had a chance to see a live demonstration of Mark Bowler and Emily Messer’s research into fur rubbing with capuchin monkeys.

"Feed me humans"

Monkey Medicine – A mini- documentary about fur rubbing can be viewed at http://vimeo.com/48287364

Then on Monday evening of the 24th of September delegates from the Animal Concepts Conference entitled Animal Welfare: Emotion, Cognition and Behaviour enjoyed two ‘talkettes’ by Prof Andy Whiten, one an introduction to the Living Links/Budongo Consortium and the other on primate minds.

The delegates also received tours of both facilities and enjoyed a brief photo shoot in the rain at our Primate Family Tree.

"Come here random zoo folk, we need a publicity photo"

Also as part of the Animal Concepts conference Dr Alex Weiss of our Living Links board gave a talk on animal personality and welfare.

"This my dear friends is a wild CHAV"

To view some of Dr.Weiss’s work on personality, visit the website below http://www.sciencedirect.com/science/article/pii/S0003347212001157

Finally, yesterday our Living Links Team presented a variety of talks to the RZSS Adult Class and again they received tours of our facilities, including a visit to the thick billed parrots with Dr Amanda Seed to see our birds partake in some cognitive research.

"If that bird shits on me again...."