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- Grand Panjandrum
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Yet another popular article, from yesterday's New York Times, on behavioural genetics....
June 10, 2005
DNA of Voles May Hint at Why Some Fathers Shirk Duties
By NICHOLAS WADE
Some male prairie voles are devoted fathers and faithful partners, while others are less satisfactory on both counts. The spectrum of behavior is shaped by a genetic mechanism that allows for quick evolutionary changes, two researchers from Emory University report in today's issue of Science.
The mechanism depends on a highly variable section of DNA involved in controlling a gene. The Emory researchers who found it, Elizabeth A. D. Hammock and Larry J. Young, say they have detected the same mechanism embedded in the sequence of human DNA but do not yet know how it may influence people's behavior.
Voles, not to be confused with the burrowing, hill-making mole, are mouselike rodents with darker coats and fatter tails. The control section of their DNA expands and contracts in the course of evolution so that members of a wild population of voles, the Emory researchers have found, will carry sections of many different lengths. Male voles with a long version of the control section are monogamous and devoted to their pups, whereas those with shorter versions are less so.
People have the same variability in their DNA, with a control section that comes in at least 17 lengths detected so far, Dr. Young said.
So should women seek men with the longest possible DNA control region in the hope that, like the researchers' voles, they will display "increased probability of preferences for a familiar-partner female over a novel-stranger female"?
Dr. Young said he expected that any such genetic effect in men would be influenced by culture, and thus hard to predict on an individual basis.
The control mechanism is also present in humans' two closest cousins, the chimpanzee and the bonobo, and bears on a controversy as to which of the two species humans more closely resemble.
Chimpanzees operate territorially based societies controlled by males who conduct often-lethal raids on neighboring groups. Bonobos, which look much like chimps, are governed by female hierarchies and facilitate almost every social interaction with copious sex.
The DNA sequence of humans, chimps and bonobos is generally very similar, but in the section that controls response to the hormone vasopressin, the Emory researchers have found the human and bonobo versions differ significantly from that of the chimp. Though not too much can be deduced from a single gene, the result shows that bonobos should be taken very seriously as a guide to human behavior and that the chimp is not the only model, said Dr. Frans de Waal of the Yerkes National Primate Research Center in Atlanta.
Dr. de Waal, who is writing a book, "The Inner Ape," said the last common ancestor of all three species presumably possessed the elements of both chimp and bonobo behavior, and that humans also "unite all these aspects."
The effects of vasopressin on the behavior of the three higher primates is not well understood, but has been studied in voles for many years. The hormone, generated by the pituitary gland at the base of the brain, makes male prairie voles form monogamous pair bonds, but has no similar effect in the determinedly polygamous montane vole.
The Emory researchers recently noticed that in their prairie vole colony, some fathers spent more time with their pups and some less. They traced the source of this variability to its molecular roots, a variation in the length of the DNA region that controls a certain gene.
This is the gene for the vasopressin receptor, the device used by neurons to respond to vasopressin. Voles with long and short DNA segments had different patterns of vasopressin receptors in their brains, which presumably changed their response to the hormone.
The long and short DNA segments differ by only 19 DNA units, mostly the same two units repeated over and over. The repeats are notorious for confusing the DNA copying apparatus, which every few generations or so may insert an extra repeat or delete one. The random changes have generated a spectrum of lengths in the voles that in turn underlies the variability in behavior, the Emory researchers say.
They proved the point by separating voles with the shortest length and longest length of DNA and showing that their progeny differed in behavior.
Dr. Young said he suspected that many other genes that influenced behavior, in voles and other species, might have fallen under similar control systems. Because the DNA repeats are so variable, they generate diversity more quickly than most other types of mutation. And a population whose individuals show a range of behavior is more likely to include some who can better adapt to a new situation.
Dr. Gene Robinson, an expert in social behavior at the University of Illinois, said the new finding was "a significant advance in sociogenomics," the attempt to explain social life in terms of DNA, because it showed how easily behavior could be changed just by altering a gene's activity, not the gene itself.
For a long time, researchers have assumed the genetic control of behavior would be too complex a problem to address. "The nice thing about this story is that it tells you it's not complex," Dr. Young said.
Copyright 2005 The New York Times Company
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