Letters — Vol. 43 No. 5

DNA Misconceptions

Carl Zimmer’s article “Seven Big Misconceptions about Heredity” (May/June 2019) makes some excellent points, and I would like to amplify a bit on “Misconception 1: Finding a Special Ancestor Makes You Special.” Using the generally accepted rule of thumb that there are three generations per century, it is possible to estimate how many ancestors a person has at a certain historical time. Because we all have two biological parents, the number of ancestors is simply two taken to the power given by the number of generations. For example, two hundred years ago would be six generations back, and the number of ancestors would be two to the sixth power, or sixty-four.

What is hard for many people to grasp is how quickly this exponential function grows. At some point the number of “ancestors” exceeds the population of the earth, and that point is not all that long ago. When the number of ancestors gets large, we must stop talking about unique “ancestors” and instead discuss “ancestor paths,” any number of which can lead to the same individual. We should think of an intertwined family mesh instead of a family tree. Using estimates of the world population, I find the approximate date at which the number of ancestor paths equals the world population to be around an astonishingly recent 1050 BCE! At this point the population of the planet and the number of ancestor paths are both about 600 million.

Going back two thousand years, or sixty generations, we learn that on average each of us has about three billion paths to any person living at that time! This shoots down the so-called “Merovingian Line” in Dan Brown’s thriller The DaVinci Code and shows that we are indeed biologically one human family.

Thomas Meyer
Ames, Iowa

Too Many Medical Tests?

In “Too Many Medical Tests” (May/June 2019), Dr. Harriet Hall makes broad claims that do not have an evidence base about how doctors think in dichotomous terms, e.g., “Doctors tend to think of tests as giving consistent and reliable yes or no answers.” Medical training emphasizes interpretation of quantifiable data, if available, as one data point in an assessment of one problem in a patient. 

“Test results are consistent and reliable” is not a myth. Our pathology colleagues are held to high standards to report “consistent and reliable” measurements. There are error bars associated with laboratory results. Anecdotes about errors or minor variations in results do not discredit our reliance on lab data to make decisions about patient care. Clinical judgment is crucial in deciding when to repeat a test before acting on the results.

The “Rules of Thumb for Patients” are simplistic and not practical for most clinical encounters. Context matters. Never say “never.” “Understand the reason for the test” sounds good. For routine tests, most patients choose to trust the professional assessment of the doctor that doing the test is appropriate. When greater-than-minimal risk is associated with performing a test, best practice incorporates shared decision-making before ordering the test. Of course, patients should “Refuse tests that are not indicated.” In reality, this applies to a small minority of the tests done every day. The problem is knowing enough medicine to evaluate whether “indications” are present.

David Lehman, MD, PhD
Associate Professor (ret.)
University of Colorado School of Medicine
Aurora, Colorado

Harriet Hall’s article “Too Many Medical Tests” is one I generally agree with, having worked with primary care development over thirty-three years. However, under her heading of Routine Physicals, she states, “But the physical exam itself can be omitted. It’s not useful to look in every asymptomatic patient’s ears, listen to his or her lungs and heart, or palpate his or her abdomen. What is useful is a directed physical exam to address any symptoms.”

Upon reading this I was shocked into the realization that this author is all about data at the expense of the person, which can be actually dangerous. I know this from direct experience with my wife’s situation, which serves as a perfect example countering Dr. Hall’s assertion.

My wife’s primary care annual physical checkup proved to be extremely fortuitous. A stethoscope examination of her heart, wherein the doctor noticed something that seemed odd and subtle, got an immediate referral to cardiology. Her aortic valve was ready to fail, and open-heart surgery was required within three months. Without her physician’s simple few moments of listening, she would have had a severe heart attack or died. Here is the kicker: she was a totally asymptomatic patient!

Such misleading statements as that of Dr. Hall can be generalized into inaction by some people (especially those hesitant or opposed to medical visits) with potentially disastrous results.

Darryl Wally
Pittsboro, North Carolina

Harriet Hall replies:

Dr. Lehman correctly points out that quality control holds tests to high standards and that medical training emphasizes judicious interpretation of lab tests. That does not negate the points I made. He says my claims do not have an evidence base, but much has been published on cognitive errors, overdiagnosis, overconfidence in test results, and harm from pursuing incidentalomas. And I have the evidence of my own observations during seventy-four years of experience as a patient and doctor: I have repeatedly seen simplistic thinking, needless tests, and over-reliance on lab tests—and have been guilty of them myself despite my knowledge. Patients may not know enough to question their doctors’ judgment, but they can always ask the doctor if the results of a test will change the management or outcome of their illness and can refuse those that won’t.

Darryl Wally offers one anecdote about heart valve disease detected during a routine physical in an asymptomatic patient. But heart valve disease commonly causes symptoms before it requires surgery, and auscultation with a stethoscope is not recommended as a screening test by the U.S. Preventive Services Task Force. It is very rare for a life-threatening problem to be detected by physical exam alone in an asymptomatic patient. Studies have shown that routine physicals do not save lives or prevent disease. Many experts, including the Choosing Wisely campaign, have called for routine physicals to be replaced by health maintenance visits with directed physical exams only to address any symptoms.

Creationist Funhouse: Red Shift

Regarding “Creationist Funhouse, Episode One: The Red Shift” (May/June 2019): Unfortunately, believers in the scientifically ridiculous may be influential in many governments.

The real difficulty for intelligent religious believers is the extreme age of the universe (not quite fourteen billion years) and its incredible size. World religions describe Creation as being for humanity! Our triviality is hard to accept.

A mere two thousand years ago a man, who indeed said many good and wise things, has today many millions of believers in his being the actual physical son of the creator of the universe now sitting at his right hand.

No one with a mere human brain capacity could possibly comprehend an omniscient god: no pope, priest, rabbi, imam … or professor! Many people need certainty, and when evidence is not present, then there will be no shortage of those proclaiming the Truth to satisfy them.

Neil McKelvie
Emeritus professor, organic chemistry, CCNY/CUNY
Forest Hills, New York

While I enjoyed Stanley Rice’s article on how creationists try to explain away galactic red shifts and apparent galactic distances as some kind of a divine hoax, I must take exception to some statements he made. While Henrietta Leavitt and Edwin Hubble both made great contributions to our understanding of a vast, expanding universe many billions of years old, they were never “collaborators,” as Rice stated. Leavitt was one of the many women “computers” at the Harvard Observatory working with glass plates showing stellar images and spectra. Her contributions were made before WWI. Hubble was an astronomer at Mount Wilson and began his career in the early 1920s as Leavitt’s was ending with her death on the other side of the country. The two never met, let alone collaborated.

Leavitt discovered the period-luminosity relationship for Cepheid variables but never established an actual distance to a Cepheid or confirmed that there were other galaxies outside of the Milky Way. As for Hubble, he never fully embraced the notion that the red shifts he discovered, which increased in direct proportion to distance, were caused by the expansion of the cosmos due to the big bang. Other astronomers, such as George Gamow and Georges Lemaitre, were the ones who truly understood what those red shifts revealed.

Dennis Middlebrooks
Brooklyn, New York

“Creationist Funhouse, Episode One” by Stanley Rice contains several errors in its description of the science of the expanding universe and the historical background of its discovery. Rice states that Cepheid variable stars in the Milky Way galaxy “all have the same light intensity.” This is entirely wrong and gives readers an incorrect understanding of how Cepheids are used to measure distances. In Rice’s telling, Edwin Hubble and Henrietta Leavitt were collaborators in the discovery of the age of the universe. This conflates and confuses their separate and independent contributions to astronomy. Leavitt’s discovery of the Cepheid period-luminosity relationship was a major influence on Hubble’s research, but Hubble’s work on variable stars in M31 and other galaxies was done after Leavitt’s death. Credit should also be given to Georges Lemaitre, who deduced the universe’s expansion prior to Hubble. Rice further distorts the history by stating that “Hubble and Leavitt detected red shifts in the light coming from all of the distant galaxies.” Leavitt didn’t work on measurements of galaxy red shifts, while Hubble’s work on the expansion of the universe used red-shift measurements that were done by other astronomers.

Aaron Barth
Dept. of Physics and Astronomy
University of California, Irvine
Irvine, California

Stanley Rice replies:

In praising both Hubble and Leavitt, I was trying to avoid the brilliant-white-man bias in science history, one that is easy to fall into. While Hubble and Leavitt were not technically collaborators, they both made important contributions. I had to leave out a lot of astronomical history, such as the story of Lemaitre, to keep my article short. I try to be careful outside my area of training (biology), but the error about Cepheid variables was my own misunderstanding. 

Gibberish about Water

One of the things I particularly admire in your publication is frequent exposure of so many false and/or misleading statements concerning methods and equipment supposedly in medicine. One such piece of equipment and accompanying unscientific, gibberish advertising is the John Ellis Water Machine.

One of the fantastic claims for what amounts to just a very over-priced still is that it changes the bond angle of water molecules. Any second-year chemistry student can tell you correctly that such a claim is false, but it gets worse. The claimed change is, according to advertising, one of the things responsible for its marvelous curative power, up to and including cancer.

Other claims include “erasing the memory” of previously tainted water, “energizing” the water by increasing the number of electrons in it, and adding oxygen to the water. The last of those claims might be correct but only if, as not specified in the advertising, the oxygen is dissolved in the distilled water by aeration. The first two claims, however, are deliberate lies or clear indications of a complete lack of knowledge of chemistry and physics. Water has no memory, a water molecule cannot have an arbitrary number of electrons, and chemically adding oxygen to water makes it hydrogen peroxide.

I hope some future issue of your fine publication will address this patent fraud.

Tim Lan
San Antonio, Texas

Joe Nickell’s “Magic Waters,” in this issue, addresses many related pseudoscientific claims and supernatural beliefs about water. —Editor

History Channel’s Bad History

Robert Sheaffer writes that the History Channel “once actually showed history” (“The History Channel Mangles Project Blue Book,” May/June 2019). Yes, and they were really bad at it. Here are some howlers I remember from those days (in the 1990s, I think). These were mistakes, not deliberate counterfactuals. But getting historical facts wildly wrong is not okay when “History” is literally your middle name.

*The battle of Gettysburg happened in July 1861. No, it was 1863.

*The first attempted launch of an American satellite (Vanguard) was in November 1956 (almost a year before Sputnik!). It was really in 1957 (first success in 1958).

*The first A-bomb test, in New Mexico, was in February 1945. No, it was July. No one at the History Channel considered how WWII might have gone differently if we had had the bomb when FDR was President and we were still fighting in Europe.

Jogn Fortier
White Bear Lake, Minnesota

Flat Earth?

If Marilyn Teed is convinced that the earth is flat, then she has not been taught science (“Flat Earth School Board Presentation Intelligently Designed,” by Craig Foster, May/June 2019). Science is about putting facts together in a coherent manner, and it is not just a collection of assertions.

The angles need not be the same, but if an object is above a plane it is visible everywhere on the plane, and if it is below the plane it is invisible. Sunrise and sunset must occur at the same time everywhere on the plane. The north star and the southern cross should be visible to everyone.

You may not live in a place where the curvature of the earth can be seen, but if you think enough about the implications of living on a plane, it becomes obvious that it is not a tenable hypothesis.

Robert Clear
Berkeley, California

So as Not to Define

Stuart Vyse (“National Down Syndrome Society Promotes Communication Pseudoscience,” May/June 2019) states that the social movement urged professionals to say “person with autism” (as opposed to “autistic”) so as not to define a person by their diagnosis. There were other conditions and diseases at the time that also changed from diagnoses, such as persons with diabetes and persons with epilepsy from diabetics and epileptics, although some persons with these conditions and diseases still refer themselves as the latter.

Frank Archer
Delta, British Columbia

DNA Misconceptions Carl Zimmer’s article “Seven Big Misconceptions about Heredity” (May/June 2019) makes some excellent points, and I would like to amplify a bit on “Misconception 1: Finding a Special Ancestor Makes You Special.” Using the generally accepted rule of thumb that there are three generations per century, it is possible to estimate how many …

This article is available to subscribers only.
Subscribe now or log in to read this article.