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The Birth of Language

Posted on August 2, 2010
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It seems like I waded into the middle of a blog brawl between Razib Khan and his dislike of linguistic anthropologists and linguistic anthropologists. Razib not only commented on this blog but also put a pointer to my entry on the death of the Bo language .

In his entry linking to my article, Razib writes:

“… this experience only reinforces my disrespect for the ‘discourse’ which linguistic anthropologists are introducing into the public domain. There are intellectual reasons to be interested in linguistic isolates not part of the big language families (e.g., Semitic, Indo-European, Niger-Kordofanian, etc.), but no language is “70,000 years old.” The Andaman Islanders are not black-skinned elves, immortals who brought their culture in toto from the ur-heimat of Africa, genetic and cultural fossils who have been in total stasis. Cultural anthropologists presumably understand that all humans are equally ancient, derived from African ancestors, and that all languages and peoples are African (or at least 95% so within the last 100,000 years), but their communication to the public confuses the issue and presents some groups as ‘pristine.’”

I had quoted what the BBC article had reported without being overly skeptical about the details. Based on his comments, I decided to educate myself a little more. A lot of things stuck out as possible outcomes from the quote, different from the one that Razib was quoting. A primary possibility was that the BBC reporter was the culprit, misquoting (I’m not saying deliberately) the linguist in question, Dr. Anvita Abbi. Another puzzling fact was that many, but not all, news outlets quoted that the Bo language was thought to be 70,000 years old. Did they all get it wrong or were they merely picking off a common source ? But, first I wanted to find out the current consensus on when language evolved.

Language is not just a means of communication, but “a distinct piece of the biological makeup of our brains”, not unlike bipedalism, as the famous linguist, Steven Pinker, put it. Language is also not the same as speech, as evidenced by the presence of sign language. And for those of us who think sign language is a fairly modern invention, a signing form of English, Steven Pinker writes in his bestseller, The Language Instinct: “They [sign languages] are found wherever there is a community of deaf people, and each one is a distinct, full language, using the same kinds of grammatical machinery found worldwide in spoken languages. For example, American Sign Language, used by the deaf community in the United States, does not resemble English, or British Sign Language, but relies on agreement and gender systems in a way that is reminiscent of Navajo and Bantu.” Finally, it is important to remember that there are languages which do not have a written form.

These three points are important to understand how we can approach the question of the origin of language. First, humans had to evolve the appropriate neural circuitry for language and they had to evolve the appropriate physical circuitry for speech. But, these two could evolve separately and distinctly. Finally, non-written languages could have been existence before the first written language or written languages could have existed prior to their being set to writing. The Wikipedia quotes the interesting case of Sanskrit, where the earliest parts of Rigveda are thought to have originated around 1500 BC while the first available written version is in the 11th century A.D.

When I asked Shanthala how old did she think language was, smart as she is, she quickly honed in on the question of how could we determine the ages of purely oral languages. If oral languages leave no fossils behind and written languages came much after oral, how can we determine when language evolved ?

We can attempt to answer the question of origin only obliquely, and with an uncertainty that only gets larger as we probe at the edges of the homo lineage. Based on fossil evidence, the oldest modern homo sapiens are dated at about 200,000 years and thought to have migrated out of Africa about 100,000 years ago. The consensus, as far as I can tell from reading the data that I could find, seems to be that human language came into existence somewhere around this period. The idea as stated by Pinker is that all branches of humanity that spread out of Africa evolved language and therefore it must have been around already when the migrations began. Debate about whether a proto language existed before then is the subject of continuing debate. The Wikipedia and especially books such as Pinker’s and Christine Kennealy’s “The First Word” are superb references for those wishing to dig deeper.

Still, is it absurd to say that a language is 70,000 years old ? Languages naturally evolve and it should at least strike one’s skeptical bone that a language could be that old. Even on the extremely remote off chance that this one didn’t, what evidence did they have to speculate its age ? I contacted Dr. Abbi to check if she had indeed said that the Bo language was that old or was the reporter misquoting her. She responded promptly:

“Yes the press has made a mistake. No language in its present form can be claimed to be that old. Linguists can reconstruct with some surety upto 10,000 years and in cases of isolated languages much longer, but certainly not beyond 15000.“

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Birdbrain

Posted on August 9, 2009
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Countless stories I heard growing up, involved animals as the main characters. In Indian mythology such as Ramayana and Mahabharata, animals played a key role, be it as the trustworthy and loyal Hanuman, the brave Jatayu who dies trying to protect Sita from Ravana or Garuda, the ride of gods. They were even the god themselves, as in Ganesha, the god with an elephant’s head. And who can forget the stories from the Jataka tales, Hitopadesha and Panchatantra with their wondrous, imaginative and moral stories in many of which animals were the only characters. When my eyes turned to the west, I ran into the cute, cuddly Mickey Mouse, Bugs Bunny, the ever grumpy Donald Duck, Elmer Fudd and the dumb, but with a heart of gold, Goofy.

The animals led lives not unlike humans in many of these tales, possessed of speech, likes and dislikes and full of intelligence and spirit. Monkeys played pranks, laughed heartily, shed tears of remorse, mice fell in love, snakes conspired and birds sang and gossiped. I knew fairly early that dogs can’t talk no matter how much Goofy does and when I saw the monkeys, realized that their lives were different from humans.

Though revered and a part of the child’s landscape across cultures, just about every culture considered them to be less than humans. In Hinduism, if you commit enough grave sins, you are reborn as an animal such as a dog or a pig. If you do good as a dog, such as give your life for your masters, you can be reborn as a human. In the west, where Christianty played (and continues to play) the central role in attitudes to animals, man ruled over the world and animals, considering it fit to use the animals as he saw fit, making it perfectly acceptable to treat them as badly as one wanted to, either by killing cats in the hundreds of thousands or rendering hundreds of thousands of animal species extinct in our path to modernity.

And animals could never be intelligent, for any definition of intelligence you could conjuncture. And could not love or mourn. If they shed tears, they were only the fake tears of a crocodile. As time elapsed and people began to study the animal life more closely, the broad generalizations of their inferiority began to fall apart. So, we constructed narrower and narrower definitions of intelligence, love and mourning to keep our superiority intact. And we showed our contempt for their minds with terms such as birdbrain. Three pieces of recent research call into question whether that is even derogatory.

Using Tools

Tools, making them and using them, were long considered the dominion of humans alone. Then people like Jane Goodall brought us observations of chimps using long leaves to tease out ants through the tiny openings in ant hills. So we grudgingly allowed some tool making capabilities to the greater apes, the primates, the ones closest to us. And though we remembered the stories of crows using stones to raise the level of water in a pitcher to a reachable level, we didn’t think they were true.

A story I came across on Yahoo news yesterday concerned new research that showed rooks, a cousin of crows, that used stones to raise the water level in a narrow pitcher to reach a worm floating in the water. The study states that the rooks seemed to understand instinctly that dropping stones would rise the level of water. Further, they also seemed to know how many to drop and learnt quickly that the bigger stones got the worm early. When presented with a bowl containing sawdust instead of water, the rooks learned that using the stones didn’t help.

The accompanying commentary to the article professes some skepticism that the rooks really understood the properties of water or that they were dropping stones instinctly rather than as a behavior learned during another experiment. I found the skepticism rather strange in trying to equate crow cognition with human cognition. I think this shows a fundamental misunderstanding of cognition and evolution. We, just like other animals, evolved in ways that were adaptive and advantageous to the environments we lived in. In other words, our intelligence is defined and limited by our bodies (mind is embodied) and the ecology in which we evolved. Birds such as crows occupy different ecological niches compared to us and so have evolved different strategies than us. Its as if the crows conducted experiments on humans ability to fly and decided that we couldn’t do it as instinctively or as well or in a similar manner as they.

The Yahoo article also posts a link to a Youtube video showing the rooks using stones to reach the worm.

This is not the only experiment that shows birds can use tools. Many other tests done in the recent past show that birds, especially of the crow family, are quite adept at using tools to get what they want.

Recognizing Faces

I came across this article last year and noted it, but failed to blog it earlier. The article speaks of research conducted in the urban landscape of Seattle. The researcher, John Marzluff, a wildlife biologist at the University of Washington, used two face masks. His team of researchers always captured a bird and banded it using one of the guises before releasing them. In the months that followed, the researchers walked the neighborhood, sometimes wearing the mask in which they captured the birds and sometimes using one that was not used in capturing the birds. They found that the birds constantly harangued and scolded them when they wore the masks that was used to capture them. And more significantly, this information seemed to have been communicated to other crows in the neighborhood because they were scolded by 47 of the 53 crows in the neighborhood, far more than the number they trapped.

Dr. Marzluff extended his study now to many parts of Seattle, used a half-dozen new more realistic masks made by a professional mask maker and added volunteers who didn’t know the history of the masks. Wearing some of the “dangerous” masks, Dr. Marzluff and his research team trapped and banded several crows in and around Seattle. Then, they asked volunteers to walk around the neighborhoods where the crows had been trapped. Unaware of the history behind the mask, some volunteers wore the “dangerous” mask and others wore a mask that had not been used to trap crows. As one of the volunteers reported:

The reaction to one of the dangerous masks was “quite spectacular,” said one volunteer, Bill Pochmerski, a retired telephone company manager who lives near Snohomish, Wash. “The birds were really raucous, screaming persistently,” he said, “and it was clear they weren’t upset about something in general. They were upset with me.”

The crows deliberately targeted only the volunteers wearing the dangerous mask even in the presence of other volunteers wearing the neutral masks. According to Dr. Bernd Heinrich, a well recognized authority in the study of ravens, this ability to recognize faces is an offshoot of the ability of crows to recognize each other even after several months of separation.

Why the mask, the more perceptive reader may ask. The researchers say they used the mask to test the recognition of faces specifically as compared to the clothing, the gait and other human traits.

Self Recognition

One of the last holdouts of our superiority over animals is self-recognition. When we look in the mirror, we know we’re looking at a reflection of ourselves. We can use this information to indulge in all sorts of narcissitic things such as grooming ourselves. Even human babies are considered to not pass muster until they’re at least a year or so old. We then grudgingly admitted that four primates, the elephant and the bottlenosed dolphin had the ability to self-recognize themselves in the mirror. But a bird, a non-mammalian life, one that doesn’t even possess the same brain machinery as the mammals, machinery such as the neocortex, thought to be the seat of self-recognition ? Not a chance.

Last year, a study found that Magpies, another cousin of the crows, can recognize themselves in the mirror. The researchers in Frankfurt, West Germany, placed a red, yellow or black mark on a group of five magpies. The black mark couldn’t be differentiated from the bird’s own black feathers. The mark was only visible in a mirror. When presented with a mirror, the birds looked at themselves and the ones with a red or yellow mark, attempted to peck themselves in the spot where the mark was.

Says lead researcher Helmut Prior: “It shows that the line leading to humans is not as special as many thought…. After finding this kind of intelligence in apes, many people thought it had developed once in one evolutionary line with humans at the end. The bird studies show it has developed at least twice”[Reuters].

The popular science magazine, Discover, listed the discovery as one of the top 100 discoveries in science for the year 2008.

It was through Kitty that I grew closer to feeling a kinship with other animals. Life with him was a continuous process of growing closer. When he first came to be with us, he wouldn’t let us touch his belly. As time passed, he allowed us to touch his belly, his front paws and finally, he sat on our laps and kneaded our chest with his paws, the ultimate act of being allowed into the feline world. The ways in which he acted with me, I wondered if he loved me. I remembered a line from Ayn Rand: “Love is making exceptions”. In that sense, I can say Kitty loved me. He made exceptions with me.

One day, we might find that it is we who’re being studied by the animals all this time, as Douglas Adams wrote tongue-in-cheek in the hilarious “trilogy in four parts”, “Hitchhikers Guide to the Galaxy”. The dolphins eventually leave Earth, having concluded their experiment on humans and in parting they say “So long, and thanks for all the fish”.

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To Walk, To Perchance Be Human

Posted on May 12, 2009
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It was a beautiful spring evening, this past Thursday. Maya was just shy of her 15th month birthday that evening, when she walked a little over a half mile.

Shanthala was on call and so Maya and I set out for an evening stroll. A neighbor walking their dog, still a puppy and not easily controlled, pushed us off our usual path. I walk Maya on the sidewalk, almost never crossing the street. I expected Maya to continue the routine. But, as we reached a traffic light on this new path, Maya stopped and gesticulated at the pedestrian crossing button, insisting that I press it. I was flabbergasted, I hadn’t realized how much she was imbuing when she was with us. I acted dumb and asked her what she wanted, to confirm that this was not a fluke. She pointed to the button and gesticulated again, this time more impatiently. After I pressed it, she gesticulated her desire to be picked up. Next, she pointed in the direction she wanted me to cross the street. I was even more surprised. This was the route when I took her running, but I didn’t think she would recognize and register this much information.

She demanded to be put down once we crossed the main street. From there, she walked all the way upto a neighborhood park. Walking with her is never a surgical operation. She stops many times along the way, examining the neighborhood, the passing cars, the passersby. She is happy to greet people who smile at her. A resident of one of the houses emerged with her 4 or 5 year old son and Maya rushed up to her, smiling and indicating that she wanted to hug the boy. All along the way, people stopped to admire this little girl, walking with such happiness.

Since Maya started walking when she was about thirteen months old, every day I take her for a walk around the block of our neighborhood. We’ve taught her to not pluck flowers, but to just touch them or smell them. So she just touches a flower or two in each bush and says “Ta”. When we get to a rosemary bush, she rubs the leaves and then rubs her face, her nose crinkling with pleasure. That spot is one of her two favorite stopping places on our walks.

Sometimes, Maya wakes up in the middle of the night and if I’m not around, starts whimpering before bellowing a full throated cry and starting her search for me. She realized that one of the spots I can be at is the toilet and so she checks there first. Before she could walk, she would crawl. Alerted by her quest by the baby monitor, I’d usually reach her before she had gone very far. Nowadays, she’s already waiting by the gate at the top of the stairs before I reach her. Since she has started walking, she rarely crawls. It is as if a switch has been turned on.

Why do we take so long to walk ? Walking involves maturation of both the muscles required and the sections of the brain responsible for controlling and coordinating the motion. The motor skills develop from head to toe i.e. we learn to control our face and neck much before we learn to control our hands and legs. Which is why babies can smile, stick their tongue out and hold their head up before they can sit, stand and walk. The motor nervous system is an incredibly complex piece of neural circuitry relying on a feedback loop to control the movements till they eventually become smooth. Many parts of the brain including the cerebrum, cerebellum and basal ganglia have to all mature before something as complicated as walking can occur. The whole process is quite hardwired i.e. little can be done by parents to accelerate it. Motor milestones (when the infants achieve a motor skill such as walking) are about the same across cultures as different as the Hopi Indians where infants are kept strapped to their mother’s back with little movement possible to modern middle class urban cultures where people attempt to give infants tummy time, kicking exercises and walkers.

Why did we start walking ? When did we start walking ?

The earliest known bipedal animal was a reptile whose fossil dates back to 290 million years. While dinosaurs and many birds (such as Ostrich) evolved to be bipedal, among primates, none are like humans in being exclusively bipedal; they’re bipedal for only some of the time. We had to undergo several structural changes to be bipedal, changes that prevent us from becoming efficient quadrupeds. For example, our hip joint is larger, shorter and broader than that of our primate cousins. Our toes are smaller, meant for motion rather than grasping as is the case with our nearest primates. One of the traits for classifying a fossil as an ancestral human (called hominins) is evidence of bipedalism. Until the discovery of the fossils of a creature named Orrorin tugenensis in Kenya in 2000, bipedalism was thought to have evolved around two to three million years ago. But this discovery dates this development around six million years old (the discovery also pushed back the split between chimps and hominins to seven million years).

We still do not know with certainty why we stood up and stayed up. Wikipedia mentions the existence of as many as twelve hypothesis that attempt to explain the origins of bipedalism. This article on Nova, the popular science show from PBS lists the various hypotheses. The one that I knew from a long time ago is called the Savannah hypothesis. As thick evergreen forests gradually disappeared and made way for wide swaths of grassland (savannah), staying on all fours with organs developed to hang from trees became less advantageous than walking. Standing up also allowed us to see farther. Another popular hypothesis is that walking endowed us with reproductive advantages. With our hands freed, we were able to carry back more food, thereby making the bipedal men more attractive to women. Another theory suggests that being bipedal allowed us to more efficiently conserve and dissipate heat. A biped apparently has a 60 percent reduction in the heat load compared to a similarly sized quadruped which in turn meant less water requirement. While many of these theories have fallen out of favor, the story remains without an end. Our bipedal origins remain a mystery.

A humorous aside. A colleague at work has this cartoon by his desk. I found this image courtesy of infiniteuser.


This evolutionary adaptation is not without its side-effects. My grandmother and my mother both suffer from severe arthritis, especially of the knee. I don’t remember my grandmother ever walking without limping, a sort of shitfing of weight to the outer side of the knee rather than directly on it, as she put one foot in front of the other. On days when her knee is tender, my mother walks like that now. Every once in a while, I take a gluosamine tablet because I’m afraid that with all my running and my mother’s genes, I’ll develop arthritis. Interestingly, arthritis has been discovered in the fossils of ancient hunter-gatherers. On Shanthala’s side, her mother suffers from severe lower back problem, something that flares up occasionally in Shanthala too.

Bipedalism also put us in conflict with our other singular characteristic, our rather large brains. Long, narrow pelvis gave way to short, wide hips to provide for a stable bipedal locomotion. This also narrowed the birth canal through which the baby had to squeeze through, putting both the mother and the baby at greater risk during delivery. We went from being gorillas with a 20 minute easy, almost painless labor to twelve hour labors, epidurals and C-sections. The small, flexible brains required for our narrow passage to the world, also meant that the brains in human infants needs a lot more maturation. Our brains continue to grow at a rapid pace, even after birth, hardly slowing down till we’re a year old.

So what came first ? The walking or the talking ? Lucy, possibly the most famous of all hominin fossils, along with much other evidence seems to indicate that bipedalism evolved before our larger brains. This is now generally accepted and some theories even argue that bipedalism may have spurred the evolution of larger brains.

Almost anything in our development can go wrong. Is there something that can make us become quadrupeds again ? In 2006, a Turkish professor, Uner Tan, reported the discovery of a family of 19 in which five individuals walked on all fours. Uner Tan dubbed the disorder, Unertan Syndrome. However, there is controversy over whether the behavior is caused by genetic defects or by the way in which they were raised. As Prof. Sean Carroll says on Nova: “The central question is not really whether a single mutation could lead some individuals to walking on all fours, but rather whether a single mutation could lead normal apes walking on all fours to walking upright. And this is completely invalid. From what we understand from both genetics and the fossil record, the process of becoming upright involved all sorts of changes in our ancestors, in our skeleton and in our musculature, in various parts of the body. And from what we understand about genetics of building those body parts and reshaping those body parts, it had to involve many genes and changes in those genes assimilated over a long period of time.”

In March 2008, an article was published in the Proceedings of the National Academy of Sciences in which the authors claimed: “Our data indicate that mutations in VLDLR impair cerebrocerebellar function, conferring in these families a dramatic influence on gait, and that hereditary disorders associated with quadrupedal gait in humans are genetically heterogeneous.” But the conclusions of this study have been refuted and there is general agreement that a single gene cannot be responsible for bipedalism.

Having reached the end of her rather long walk that Thursday evening, Maya sat down on the sidewalk by the Stop sign that marked 0.53 miles. I picked her up and carried her back to the house. But she was not done yet. She didn’t want to get back in and so we continued our walk around the block. Around the corner from our street, sprinklers came alive, spraying water onto the manicured lawns, spilling some onto the sidewalk. Maya ran towards the spray, stretching her hand out to feel the water. She looked at me and not seeing any sign of disapproval, waded into the middle of the lawn, screaming in delight at the water spraying her from all directions. I took her home a few minutes later. She was soaked, and deliriously happy.

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Babies Make Us Human

Posted on March 4, 2009
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All things baby interest me, especially if they’re related to evolution or cognitive science, because in the end those fields help us understand what it means to be human. In today’s NYT, there is a fascinating article by Natalie Angier (of the Canon fame) about the ideas of a renowned primatologist and anthropologist, Sarah Blaffer Hrdy, specifically the idea that we “became the nicest apes before the smartest apes” and this had to do with infant rearing. From the article:

“Through its ability to solicit and secure the attentive care not just of its mother but of many others in its sensory purview, a baby promotes many of the behaviors and emotions that we prize in ourselves and that often distinguish us from other animals, including a willingness to share, to cooperate with strangers, to relax one’s guard, uncurl one’s lip and widen one’s pronoun circle beyond the stifling confines of me, myself and mine.”

It is generally accepted that raising kids in a nuclear family of two adults is a post-WWII, US and Western Europe-centric habit. Throughout most of human existence on this planet, and even today in many cultures outside US and Western Europe, infants are reared by more than two people. Joint families that include living with at least the parents on the father’s side is very common in India, for example. In many cultures including India, the older siblings share the responsibility of raising a younger sibling, especially after the infant has been weaned. My father, the eldest son, told me how as a child, he had to rock the cradle while his younger sister slept. He said, “If she was awake, I was off the hook. I’d get so bored sometimes rocking the cradle, I’d pinch the baby and wake her up.”

Allomothers is the technical term used for like-a-mother caregivers of an infant. Cooperative breeding is another term used to describe the same principle. It is a reproductive strategy that has the potential to allow the females to reduce the time between offspring by reducing the burden that she alone has to carry. In apes such as chimpanzees and gorillas, primatologists observed that the mother was left to raise her offspring on her own. Another male or female is likely to kill another’s infant to increase the chances of survival of their offspring. A mother therefore guards the baby and refuses it to be carried or handed over to another member of the group.

For a behavior to be selected, there must be an advantage to all parties involved. The benefit to the mother in allomothering is clear, but what is the benefit to the allomother ? If it is the father, the benefit is again clear, his offspring survive. But if the allomother is not related, what is the benefit ? The currently accepted hypothesis is that caring for other’s infants makes a female a better mother and therefore increases the chances of survival of her offspring. If this hypothesis were true, then inexperienced females should tend to provide allomothering compared to experienced females and the offspring of allomothers should have a higher survival rate than those of non-allomothers. Sarah Hrdy’s study of Hanuman Langur monkeys at Mount Abu in India provided support for this hypothesis. She found that females who had not been mothers yet were willing to be allomothers more often than females who already were mothers. Lynn Fairbanks found that in vervet monkeys, females with high alloparenting experience had a 100% success rate in raising their offspring to maturity while the inexperienced females had only a 50% success rate.

Multiple points of data support the idea that humans evolved to be cooperative breeders. A recent article in ScienceDaily quoted a study by an anthropologist, Barbara Piperata, which stated that because of social support during the breast-feeding phase (upto about 18 months), mothers are able to conserve their energy and become fertile more rapidly compared to other apes which lack such a social support. Another theory that I came across in Meredith Small’s “Kids:How Biology and Culture Shape The Way We Raise Our Children” is based on the observation that humans are unique among the great apes in having a childhood, a stage where an infant has been weaned but is still dependent on adults for feeding and protection. Other apes go from infancy to juvenile phase without passing through a childhood phase. The reason we evolved to have a childhood, according to this theory (by Dr. Barry Bogin), is because older siblings can be alloparents, reducing the burden on mothers and freeing them to reproduce sooner. These two theories state that these are the reasons why humans can reproduce every 2 or 3 years, double or triple the rate of our other great ape cousins, the gorilla and the chimp, which reproduce only every six or seven years.


When I explained all this to Shanthala, she told me about the evolutionary reason for menopause. It’s called the “Grandmother Hypothesis”. Women have menopause because this allows them to be allomothers, help raise their grandchildren instead of continuing to invest in their own offspring. Dr. Hrdy argues that recent research has overturned the idea that humans are a patrilocal society i.e. women join the husband’s family. When it comes to raising an infant, women frequently return to their birth homes, using the experience and help provided by her mother. This custom is true in Indian culture. My mother (and I suspect that’s true for most of my generation) came away to her parent’s place when she was in the final stages of her pregnancy. My father was not even there when I was born and it would be six more months before my mother and I returned to join my father. This tradition continues with a slight twist for all of us immigrant families. Since most immigrants to this country consider it advantageous to give birth here than back in their home country, the women’s parents come to stay with them for an extended period during this time. In many cases, it is the only time the wife’s parents ever come to this country to visit their daughter.

All this is old hat, in some sense. What the NYT article talks about is Dr. Hrdy’s hypothesis that many facets of human behavior are better explained because we’re cooperative breeders than by the fact that we have complex brains. For example, to allow others to raise your infant, you must be willing to trust them; both must evolve a theory of mind i.e. be able to place themselves in the other’s shoes and empathize with them, be able to understand what they might think and feel in a given situation and respond appropriately. She argues that we developed our complex emotional behavior long before we evolved larger brains. She offers evidence of cooperative breeding in other animals such as lions and meerkats that you don’t need large brains to evolve cooperative breeding.

According to the NYT article, Dr. Hrdy has her bias in putting forth this new theory. From the article:

“Dr. Hrdy wrote her book in part to counter what she sees as the reigning dogma among evolutionary scholars that humans evolved their extreme sociality and cooperative behavior to better compete with other humans. “I’m not comfortable accepting this idea that the origins of hypersociality can be found in warfare, or that in-group amity arose in the interest of out-group enmity,” she said in a telephone interview. Sure, humans have been notably violent and militaristic for the last 12,000 or so years, she said, when hunter-gatherers started settling down and defending territories, and populations started getting seriously dense. But before then? There weren’t enough people around to wage wars. By the latest estimates, the average population size during the hundreds of thousands of years of human evolution that preceded the Neolithic Age may have been around 2,000 breeding adults. “What would humans have been fighting over?” Dr. Hrdy said. “They were too busy trying to keep themselves and their children alive.”

Having returned from a five week visit to India, I’m now alone again in caring for Maya the days that Shanthala is at work. In India, the task was made somewhat simpler because of all the help that we had in caring for Maya from our parents and friends to household help. All this talk of cooperative breeding makes me rather envious, and a little sad.

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Parental Control

Posted on November 27, 2008
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Since Maya was born, people have been constantly opining which one of us she looks most like. Some see in her the spitting image of my family’s characteristics, some see Shanthala in her, some say that she looks like me but her eyes are unlike either of us, Shanthala herself says that Maya’s chin is unlike either of us. Comments pass from her features to her skin color. She’s much fairer than either of you, some have said while others have said that she has Shanthala’s skin tone. And then they’re amazed at her height (she’s in the 95th percentile for her age and sex) and wonder where that characteristic came from.

Shanthala and I joke (with a hint of seriousness) about the roots of Maya’s seeming impatience or her easy, smiling nature. My parents compare her to my sister in terms of how easy she seems to be to care for. Many say that girls are easier to raise than boys. Maya had a lot of eczema till recently. While she never seemed bothered by it, Shanthala and her parents worried that her skin maybe as sensitive as Shanthala’s was and that she may suffer from skin irritations.

All this is boringly normal, this ongoing back-and-forth between who a child looks more like and which characteristic comes from whom. But it appears that the battle rages inside in very fascinating ways.

It is well understood that a child inherits half the genes from the biological mother and half from the biological father (in a world of donor eggs, donor sperms, surrogate mothers and adopted children, the simple terms mother and father have become too narrow to capture the reality). Typically both copies of the genes are active in the child. But in a less than one percentage of them, one of the copies is turned off. In some cases, it is the mother’s copy that is turned off and in some cases, it is the father’s. Wait, you say, isn’t this what I learned in school about dominant and recessive alleles ? About how blue eyes are a dominant gene over brown eyes and so gets expressed ? Isn’t this what you’re talking about ? Sure, this is true only if both copies differ from each other, not if they’re similar. Also, the discussion revolved around whether a particular gene was dominant over the other.

Here is where a newly discovered technique differs. In some small percentage of cases, the same gene sequence will express a different behavior in the offspring depending on which parent’s copy is turned off. For example, if the copy comes from the mother it produces blue eyes and if it comes from the father, it produces brown eyes (the color of the eyes is used for illustration, it is not a real example of this technique). This seems absurd. The same gene sequence should produce the same behavior, independent of the source of the gene. This mechanism of inheritance where the behavior is determined by which copy of the parent the gene comes from is called gene imprinting (or genomic imprinting) i.e. which parent’s imprint is retained in the offspring’s copy. It is now considered a separate process of inheritance compared to the classical Mendelian genetic inheritance.

But wait, gene imprinting gets even more interesting. In an interview with the magazine Edge, the evolutionary geneticist explains:

This is a complicated process because the imprint can be erased and reset. For example, the maternal genes in my body when I pass them on to my children are going to be paternal genes having paternal behavior. If my daughter passes on paternal genes to her children, even though she got the gene as a paternal gene from me it would be a maternal gene to her own offspring. Molecular biologists are particularly interested in understanding the nature of these imprints, and how it is possible to modify DNA in some way that is heritable but can then be reset.

This would be merely fascinating if it didn’t have startling consequences on the offspring. There are children who always smile and laugh, but sadly also have symptoms that are similar to those with severe autism and they mostly never learn to read or write. Some other children almost not nurse as infants forcing them to be tube fed but in a few years time, they develop an insatiable appetite and develop schizophrenia. The first suffer from a genetic disorder called Angelman syndrome and the latter suffer from a genetic disorder called Prader-Willi Syndrome, the first is caused by mutations to the paternal gene imprinting and the latter is caused by mutations to maternal gene imprinting. Many scientists now speculate gene imprinting to be the cause of many problems that plague us humans from asthma and diabetes to cancer. The reason for this is that one of the copies from the parent is bad, the other copy is present to be used. But in case of gene imprinting, the good copy is turned off and only the bad copy retained, making the offspring more susceptible to disorders.

In 1999, David Haig offered an intriguing hypothesis that suggested that in the battle for imprinting the child, each parental genome approached the union with a view that was beneficial to their side. Evolutionarily, for a mother, it is important to spread her efforts amongst all her children, striking a balance between putting all her eggs into a single child and spreading herself too thin by having too many of them. For a father on the other hand, it was more useful to ensure that his child got the most attention (and resources) from the mother compared to other children (biologically, monogamy is a culturally induced trance, and one that is frequently broken). Thus, mother’s side of the gene pool was growth moderation while the father’s side was growth promotion.

Interestingly, gene imprinting is not known in animals other than mammals. Platypus, for example, the earliest mammals, do not have any genes that are imprinted.

In a recent article in the science magazine, Discover, the excellent science writer, Carl Zimmer, explains all this and takes it one step further. He quotes the work of two evolutionary biologists, Bernard Crespi and Christopher Badcock, who suggest that “our minds too are shaped by this battle between the parental genes”. They hypothesize that autism and schizophrenia are the two faces of this evolutionary conflict between the parental genes expressed in the brain. Carl writes:

One of the most striking contrasts between autism and schizophrenia is how they affect the ability to understand others. Autistic people have a difficult time figuring out what other people are feeling. Schizophrenic people, on the other hand, sometimes do too good a job. They may come to believe that a refrigerator is talking to them, for example, or that people are conspiring against them.

Crespi and Badcock propose that these symptoms result from the genetic conflict. Empathetic children can see how frazzled they’re making their mothers and how much attention their siblings need. Maternal genes should therefore boost our abilities to get inside other people’s heads. Paternal genes, on the other hand, may benefit by reducing these distractions from the business of getting more resources from mothers.

Life is such a wondrous miracle. I’ve often times felt puzzled about how people can accept a simple explanation such as god when there are such fascinating explorations and reasons which can explain how this miracle actually happens. Most of the time, all goes well and we end up with a healthy, normal child. Most of the time. On this Thanksgiving Day, I want to offer thanks and express gratitude for the turns of time that have placed Shanthala and I where we are, with who we are and how we are. And of course for the healthy gift of life that almost didn’t happen, Maya.

References:
- Imprinted And More Equal, American Scientist, 2007
- GeneImprint: The main technical website that discusses everything pertaining to gene imprinting
- Alleles & Inheritance: A webpage discussing the difference between normal and imprinting inheritance

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