“How to Build a Dog,” by Lyudmila Trut and Lee Alan Dugatkin, describes a decades-long experiment in Siberia in which foxes were selectively bred for tameness, resulting in physical traits we associate with dogs. Turning a fox into a dog certainly offers insight into how our ancestors tamed other animals. But maybe it also tells us something about how we tamed ourselves, changing from apes to modern humans.

The authors describe juvenile facial characteristics as a component of the so-called domestication syndrome, and it does distinguish us from our closest living relatives, chimpanzees and bonobos. Further, docility is certainly necessary for large groups of humans to cooperate in urban environments, even if it also predisposes us to “follow the leader,” for good or for ill.

Fifty generations of foxes could be bred in a single person's lifetime, whereas 50 generations of humankind still take us back only 1,500 years. How much have we been domesticating ourselves in the 10,000 years since agriculture and the first cities? Culture may be capable of driving biology faster than we realize.

PHILIP EARLY Bainbridge Island, Wash.

The article on making a dog from a fox reminded me of the history of the greyhound, where, in the opposite direction, many traits from the wild were accentuated in a domesticated animal through the process of breeding.

When I adopted a retired racing greyhound, a little research showed how breeding purely for speed had led to many anatomical similarities with cheetahs. (For example, both have long legs and a long body and neck and a deep chest.) As with the doglike foxes in the article, unnatural selection greatly sped up this “evolution.” Greyhounds remain dogs at heart, though. They take retirement seriously: we call them 45-mile-per-hour couch potatoes.



Thank you for “A March for Science Is Not Enough” [Science Agenda], the editors' column on the need for scientists to do more than march to turn the president, Congress or state legislators away from “policies likely to increase pollution, harm health, reduce our ability to forecast natural hazards ... and toss accepted science out the window.”

Vastly increased political influence is necessary, and that requires a full-scale social movement that can not only lobby but keep the pressure on with a range of activities that make business as usual impossible. We are ignoring a wheel that has been invented. Only such movements—which brought about the fall of apartheid and segregation—can beat powerful interests. Movement-building requires grassroots organizing, which extends far beyond the scientific community, as the editorial notes. Unfortunately, those concerned with the health of the earth and its creatures pivoted from grassroots organizing in the 1970s and opted for big nongovernmental organizations that depended on check writers and played an exclusively insider game. We have lost political influence since then. Check writers don't change the world. They lack the passion and commitment of activists.

Part of the problem may also be that most of us are middle class. We have too much vested in the status quo. We have careers. We really don't want to take on population, consumption or those with great power. We don't want to stand the world on its head. It's risky.

As a veteran of the movements for U.S. civil rights, against the Vietnam War and against South African apartheid, among others, I believe that until we are willing to organize, we aren't going to make much of a difference.

DAVID JOHNS Hatfield School of Government, Portland State University


In “Missing Links,” Philip L. Reno describes finding stretches of DNA that have long been present in various mammals but that had been turned “off.” Then the ancestors of we humans came along, and the “off” switches—stretches of noncoding DNA—were removed, which allowed certain proteins to be produced that gave us traits that make us a unique species. This seems to cause a problem for the currently accepted Darwinian method of evolution.

Apparently one of the affected genes, when turned on, allowed the brain to grow larger by not pruning neurons. Charles Darwin proposed that species' traits were created, by random mutation, at the time they were “needed” (that is, genes that aided in survival endured as soon as they appeared). Yet this case seems to require that a gene be provided long before it was needed, along with the necessary machinery to keep it inactive. It seems impossible that such a mechanism could be created by random processes that would work perfectly millions of years after it was made. Inactive DNA is supposed to be removed, as eyeless animals that live in caves attest. Do I misunderstand the process?

CARL COX Mansfield, Mo.

RENO REPLIES: I would like to correct Cox on a few crucial areas. The stretches of DNA that humans lost were not “off” switches but “on” switches, key regulatory sequences for genes. Our hypothesis is that when certain genes were turned off, or expressed to a lesser degree, this limited the number of neurons pruned and allowed for a larger brain. The genes and their switches were not developed before they were needed but rather were active in many mammals, including our ancestors. We propose that humans had turned them off via DNA deletion. This is perfectly in line with Darwinian theory. Random deletions occur as a form of mutation all the time (on an evolutionary timescale). Usually deletions will have no effect or be detrimental.

Yet sometimes the loss of key regulatory sequences can alter gene expression in ways that produce beneficial changes in animals, including humans. And although a cave fish may evolve eyelessness because of the costs associated with developing and maintaining an organ that provides no benefit, there seems to be little cost to keeping around a few extra billion base pairs of DNA in our genome.


In Lee Billings's review of Apollo 8: The Thrilling Story of the First Mission to the Moon, by Jeffrey Kluger [Recommended], the flight of the Apollo 8 astronauts was described as the first time humans escaped Earth's gravity. Technically, Apollo 8 did not reach a sufficiently high velocity to break free of Earth's gravitational field, although its crew members were the first humans to leave the planet's orbit.


In “Schizophrenia's Unyielding Mysteries,” by Michael Balter, the box entitled “Research Dragnet Falls Short” incorrectly referred to there being 23 chromosomes in the human nucleus. There are 23 pairs of chromosomes, or 46 in all.