Darwin in the Crib

Last week my editor at the New York Times asked me to write an article about the evolution of crying, to accompany an article by Sandra Blakeslee on colic. Both articles (mine and Blakeslee's) are coming out tomorrow. As I've written here before, human babies are by no means the only young animals that cry, and there's evidence that natural selection has shaped their signals, whether they have feathers or hair. Among animals, there's a lot of evidence that infants can benefit from manipulating their signals to get more from their parents. On the other hand, evolution may sometimes favor "honest advertisements" that prevent offspring from deceiving their parents. Human crying may be the product of the same conflict of evolutionary interested between parents and children.

This was a tricky article to write, because on the one hand there are some very interesting ideas to examine, but on the other hand, they're only hypotheses that haven't been put to much of a test in humans. I've come across two big papers in the past couple years, this one by Jonathan C.K. Wells in the Quarterly Review of Biology in 2003 and another by Joseph Soltis in the latest issue of Behavioral and Brain Sciences. They offer and evaluate a number of hypotheses for human crying. They even give some thought to colic, that maddening far end of the crying spectrum where perfectly healthy babies cry for hours, turning their parents into shambling wrecks. According to one hypothesis, colic is just a case of deceptive signals from child to mother, carried to an absurd extreme.

These are just preliminary hypotheses, though, and they face a lot of tough tests. As I mention in the article, chimpanzees show no sign of colic, which makes you wonder how deep the evolutionary roots of colic could go if it is not found among our closest living primate relatives. What I didn't have room to mention in the article were some comments published in response to Soltis's paper in Behavioral and Brain Sciences by Hillary Fouts of NIH and here colleagues. They study foraging societies in Africa, and in their years of observing how these people raise kids, they haven't seen any colic either.

One way to account for this pattern is the possibility that colic is a disease of affluence--an adaptation turned maladaptive in the modern age, like a taste for sweets that was once satisfied by fruits and can now be drowned in a sea of high-fructose corn syrup. Wells even suggests that the modern Western food supply may have cut down the cost of crying, making it easier for kids to cry more. In foraging societies, mothers nurse their children up to four times an hour, while mothers in farming and industrial societies nurse their babies far less. Babies also cry to be held (perhaps for warmth and protection from attack), and while foragers hold their babies constantly, Westerners keep their babies separated from them much of the time in cribs, carriages, and car seats. Wells suggests that when a colicky baby sends its cranked-up signal and doesn't get the right response, it cranks up even more.

Again, this is only a hypothesis--a starting point for investigation. Hillary Fouts and her colleagues show what this sort of investigation can look like. In the latest issue of Current Anthropology, they report on a study about the end of crying, comparing how babies respond to weaning in two cultures. Both cultures are found in the same rain forests of the Central African Republic. One group live as foragers, and the others as farmers. The foragers nurse their children many times a day and wean them by gradually taper off nursing. The farmers, on the other hand, cut off their children abruptly--in part because the women need to get back to working in their fields.

Fouts and her colleagues found that the farmer children fussed and cried a lot around the time of weaning, while the forager children didn't show much difference. But the researchers kept following the children and found something interesting: the farmer children stopped fussing before long and then cried a lot less in general. The forager children, on the other hand, kept crying more than the farmer children long after they had been weaned.

Fouts and her colleagues see a subtle strategy at work here. The farmer children may cry in response to weaning because it represents the end of a reliable milk supply and perhaps even because weaning raises the odds of their mothers will get pregnant with another child that will compete for the mother's investment. But once the farmer children are weaned and it is clear that their cries will not do them any more good, they don't waste any further effort on the tears.

The forager children, on the other hand, don't get that clear signal of an impending cut-off, and so they don't fuss and wail more in response. But it's also important to bear in mind that in the foraging community, the children are always around some relative who will be quick to pick up a child. So even after weaning, crying still has some value as a signal, and so the children keep it up.

What I find particularly interesting about this study is that it suggests that we shouldn't use evolution to manufacture a false sense of nostalgia. Just because our ancestors lived in a particular way doesn't mean that the way we live now is automatically bad. Our evolutionary heritage is not completely fossilized; it can in some respects alter itself in response to the conditions in which we grow up. If colic follows this pattern, it is not a cause for collective Western guilt that we don't live as foragers. Instead, it's a call to understand the evolutionary roots of the behavior of our children--both for their well-being and our own sanity.


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I enjoyed reading and was informed by the Loom post and linked NYT articles. The material caused me to reflect on my personal experience with crying and crying babies in my family.

Im the oldest of a multiple sibling family. As the Alpha sibling I got to observe and participate in the rearing of six human primates, my brothers.

Based on observed crying data from that sample size of six, and considering the Loom and NYT reporting on crying, I must conclude that some of my brothers were raised and nurtured by a forager mother and the rest by a farmer mother.

As for me, being No. 1 Me Maw liked me best of course. As a result, I was reared neither as a Forager nor a Farmer, but rather as a Golden Child. So I had nothing to cry about.

By Joseph Poliakon (not verified) on 07 Mar 2005 #permalink

Interesting article....I am the father of two teenaged daughters and as an infant, my older daughter was "fussy"....not to the point of colic though. I always assumed that colic was a medical condition, not an emotional one as presented here.

I guess that the cure for colic is simply to carry the baby more...

By Ken Shackleton (not verified) on 08 Mar 2005 #permalink

Crying also is used to rid the body of noxious chemicals. Might it not also serve that function in vulnerable children who must eat whatever offered? As for signaling, shouldn't the evolution of the crying behavior be viewed in tandem with brain evolution (and especially female brain evolution), since they must have coevolved?

Interesting... yet provocative! I believe crying is different from colic. Crying is a communication method for babies with their caregivers, and a vital kit for survival, thus conserved through evolution. The benefits of crying are not be one-sided because parents have vested interests in their babies' well-being and crying helps protect and raise fit offsprings.

Colic, on the other hand, can be considered as an extreme and dysfunctional form of babies' communication method because it no longer serves its originally intended purposes. I cannot think of any evolutionary benefits for conserving this behavior. I am not even sure whether this could be considered one of normal human behaviors or developmental stages.

Colic is rare... I believe, only more common in the Western hemisphere. When a baby, say, does not get what she wants, she communicates by crying. When this signal is not responded properly, if this becomes patternized, some babies learn and stop crying; others are more stubborn or slow to learn and keep crying, sometimes become colic. That's how I would see colic.

Reading Dr Karp's five steps, I initially anticipated some magic tricks. They turned out nothing more than what my wife and I practiced when our infant daughter cried several years ago, although they are not exactly word-to-word. We wrapped her snuggly, held her (sometimes for hours each time), rocked her, hummed to her, did everything we could to calm her down. It was not easy, but she has never been colicky. And who says partenting is easy?

I doubt if any "colic" genes could ever be cloned. I doubt if this is an evolutionary phenomenon. I believe it is a social problem that can be cured with lots of care, attention, and proper parenting.


I have 3 sons, now 22, 16 and 14. As babies, they each benefited from strategies their mother and I developed in response to crying. The first boy would sleep well after feeding. He liked to suck his dummy and would wake up when it dropped out of his mouth. the solution was to twist a nappy or nursing cloth into a stiff length of material that would not unravel.

The dummy was secured at one end and placed in his mouth with the other end tucked under his mattress. This worked very well. As he grew stronger he learned to find the dummy if it fell out of his mouth. Problem solved. Mind you, we negotiated over the years to persuade him to give it up finally. In the weeks before his 4th birthday we suggested he be the one to put it in the bin and lo, it worked.

Second boy, very different! His mother was very depressed after the birth. I took over and would sleep with the little mite on my chest in the spare room. It was wonderful. I shall never forget those months as long as I live. The boy and I are very close. Number three was born one month before his mother and I parted. Work committments had kept me away from home and we grew apart.

For the two elder boys, then 3 & 8, they now would stay with me at my house from Friday evening until I dropped them off with their mother on Monday morning on the way to work. The baby boy stayed at home with his mother and her new partner until he was 3. By this time he knew I was his father and wanted to join us at the weekends. He had been that oddest of creatures, a model baby. No colic, no fuss, happy as a sand boy. It was as if he knew times were difficult and had decided to make the best of it.

Foraging or farming? Babies have personalities. Some cry easily, others are tougher. What I am convinced of is that it takes an extended family or hired help to raise babies. It's way too tiring to do it alone. Now the two younger boys have chosen to live with me. The eldest uses his mother's house as a hotel. All in all we are a co-operative family, reasonably sane and the chaps all know that if they look like they want to make me a grandfather, I'll have them neutered. Raising a family is exhausting, wildly expensive and long term. I'll never be able to retire. I am 62 and kids don't leave home until the are 30. That's another 16 years. I think I feel an attack of colic coming on. Bah Bah BAAAA.