Shaking up the system
I read “Pushing PhyloCode” [April] with interest. I sympathize with the proponents’ desire to improve the classification system, but I cannot agree with all of what is proposed. The current Linnaean system of naming species has an elegant simplicity and utility. One simply takes the genus name, which is a noun, and modifies it with an adjective, or species epithet. Thus Homo sapiens means “thinking man,” and Homo erectus means “upright man,” and so forth. The scheme presented in the article, which proposes dropping the binomial system and keeping only the epithet, so that instead of Homo sapiens the scientific name for humans would be sapiens Linnaeus 1758, would be a source of mass confusion among scientists and the public. There is only one Sciurus carolinensis, but there are many species that use the epithet carolinensis. The epithet is meaningless without the genus. How would we function with just a bunch of epithets, discoverers’ names, and dates? Any proposal to revise taxonomy should leave the binomial system intact.
John C. Jahoda, professor of biology
Bridgewater State College
The other side of darkness
In April’s Sky Lights [“A Lighter Shade of Black”] Bob Berman presents the paradox suggested by astronomer Heinrich Olbers: “If we live in an infinite universe containing an infinite number of stars, then . . . every point of the sky, no matter how small, should be filled with starlight. . . . So why is the sky dark?” His answer: “The sky is dark because the universe is young. Its 13.7-billion-year age has just not allowed enough time for the light from most of the cosmos to reach us.” Not so. There are patches of sky that appear dark, but not because there is no light coming from those points. Every point of the sky, no matter how small, is filled with light at microwavelengths. The sky is dark because the expansion of space prevents some light from appearing in the visible range of the spectrum. Thirteen billion years ago, those same stars were nearly 13 billion light-years closer to us, but they were no more visible then than they are now.
Grand Rapids, Michigan
There is more than one “solution” to Olbers’s paradox, and even astronomers disagree about which is the most meaningful. Bob Berman focused on the one generally favored by the scientific community. The key point is that the paradox shows that the universe must be finite in age, size, or both (assuming the universe is uniformly full of stars). Cosmic expansion effectively puts a finite size on the visible universe, which is another way of saying that distant light is redshifted to low energies, and the light from even more distant objects is cut off from us entirely. (The most distant light is not starlight at all, of course, but leftover energy from the Big Bang, now in the form of microwaves.) The finite age of the universe also solves Olbers’s paradox, even if we lived in a static universe. —The editors
Faith and the embryo
Biochemist Paul Berg suggests in April’s Discover Dialogue [“Bio Brain Backs Stem Cells”] that only religious faith makes the judgment that the destruction of a human embryo destroys a human individual. This isn’t a question of religion. Though I lack faith, I still acknowledge that there’s no such thing as a generic embryo. While a blastocyst contains undifferentiated cells, it is an individual organism with its own agenda. The question is not whether an embryo is an individual of a certain species but whether all human organisms have rights to life, liberty, and the pursuit of happiness merely by the fact of being human.
The Mercury Debate, Part Two
The alarmist article “Our Preferred Poison” [by Karen Wright, March] provides so much misinformation that dentists, physicians, and dietitians will be busy reassuring patients who have read your article that the sky is not falling. Dental amalgam is a stable alloy made by combining mercury with silver and other metals. While it contains mercury, dental amalgam has entirely different physical and chemical properties from mercury by itself. Common table salt contains poisonous elements such as sodium and chlorine. Should we stop using these for fear of being poisoned? Major organizations entrusted with protecting the public’s health, such as the World Health Organization and the U.S. Public Health Service, believe amalgam is a safe, effective material to treat cavities.
James B. Bramson, executive director,
American Dental Association, Chicago, Illinois
Much of the information in my article came from a report published in 2000 by the private, nonprofit National Research Council. The authors of the report conclude, based on studies done in the 1990s, that “Hg [mercury] vapor from dental amalgams enters tissues, including the brain,” and probably accounts for the mean blood concentration in the U.S. population of between 5 and 10 micrograms of mercury per liter. No one can say whether that level of exposure is safe. Even the U.S. Public Health Service, which maintains that dental amalgams cause no harm, notes in a consumer update that ongoing studies “will require several years of follow-up in order to detect any subtle and long-range health effects.” —Karen Wright
The high cost of conformity
Congratulations on your story “20 Years Ago in Discover: Misunderstanding AIDS” [R&D, April]. You have the courage to admit a mistake. The story illustrates an important lesson: Scientific and medical truth is not determined by majority vote. Your editor John Langone interviewed more than a dozen “experts” for the original 1985 story who agreed, incorrectly, that there was little risk that HIV and AIDS would be transmitted heterosexually. I was the only dissenting voice. Unfortunately, history has proved that I was correct. Another observation: Those who challenge orthodox opinion are labeled “controversial,” an appellation that sticks even when the controversial opinion becomes accepted wisdom. My advice to young scientists and doctors: Call it as you see it. Your controversial idea may be correct!
William A. Haseltine, president,
William A. Haseltine Foundationfor Medical Sciences and the Arts
Erratum: In May’s Letters, we printed the following from a letter by reader Sandra Duffy: “As a lawyer who has tried over 100 mercury poisoning cases since 1978, I can tell you that there is no substantial evidence to support a conclusion that any level of mercury exposure is safe.” The sentence should have read, “As a lawyer who has tried many cases since 1978 (over 100) . . .” We regret the error.