“Monsters of the Mesozoic Skies,” Michael B. Habib's article on pterosaurs, gives the best discussion of their likely flight mechanisms I have ever read! Some birds with large heads and bills, such as pelicans, fly with their neck retracted over their back so that the weight of the head and bill are close to the shoulders (and thus the center of lift). Would such a posture be a way for pterosaurs to maintain better balance during flight?

College of William and Mary

What was the advantage of pterosaurs having such large heads and long necks? Habib describes how flight may have proceeded from a leg vault to a wing catapult to launch. It appears to me that an important additional motion was employed: a sudden upward jerk of the head during launch. This impulse would have utilized the strong neck muscles and long neck to snap the large head upward, providing vertical momentum. Were the utility of this impulse critically important for pterosaurs to launch, it would help explain the evolutionary advantages of some of their ubiquitous morphology.

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As pilots know, an aircraft's vertical stabilizer and its associated rudder are essential for controlled flight. I wonder if the aerodynamic consequences of the large crested heads of these creatures has been investigated.


HABIB REPLIES: I want to thank readers for their fantastic engagement with a subject that I will continue to probe at the Dinosaur Institute of the Natural History Museum of Los Angeles County. Regarding Ware's thoughts: it turns out that pterosaurs' necks were not very birdlike. Rather than having numerous, small, highly mobile neck vertebrae, they tended to have a handful of large ones with fairly average mobility. In the longest-necked pterosaurs, the neck vertebrae were actually interlocking, making the neck quite stiff. As a result, there was no way for them to arrange it in a classic birdlike S curve.

In response to Sproul: The head and neck might have been raised quickly during launch to help give a bit more rise to the center of mass. Pterosaurs could also have moved their head and neck in flight to quickly change the center of mass and thereby improve agility.

To answer Magathan's question: The crests do indeed look like vertical stabilizers or rudders in some species. But flying animals do not use (or need) those mechanisms because they employ a different distribution of lift on their wings as compared with aircraft.


In “A Significant Problem,” Lydia Denworth presents some of the major controversies regarding the use and misuse of null hypothesis significance testing (NHST) in published medical and behavioral science studies. She also mentions a special issue of the American Statistician concerned with these problems, and I happen to be one of the statisticians who contributed to it. A big part of the problem is science journals' widely cited publication bias, whereby reports showing positive effects in support of hypotheses receive preference. Given this bias, is it any wonder that there is a “replication crisis”?

Publication bias can be largely circumvented by preregistering studies judged methodologically sound with journals before their results are in. Yet an almost equally effective and less cumbersome method that could be more seamlessly adopted would be results-blind manuscript evaluation (RBME), whereby the editor distributes only the introduction and methods sections to reviewers for a first-stage provisional decision on publication acceptance before the results are seen. (The Results section would be edited in a second stage if the first-stage provisional decision is for acceptance.) Authors would be made fully aware of the RBME policy to also reduce any incentive to consciously or unconsciously distort results in a more positive direction or to fail to report valid null findings. Such a procedure bases publication solely on the judged importance of the research question addressed by the study and the quality of its methodology, not the results.

Harvard Medical School


“Closing the Skills Gap,” by Rick Lazio and Harold Ford, Jr. [Forum], is an interesting (if incomplete) article arguing for reform in education to better serve a need for workers in STEM that would have been improved if the acronym had been defined in the narrative (it stands for science, technology, engineering and mathematics).

Although I don't disagree that the educational system is failing us (particularly in minority communities), the authors are overlooking another gaping hole: not everyone is destined to (or interested in) becoming a scientist, engineer or mathematician (or even graduating from college). The current system is also sorely lacking in encouragement, opportunity and training for those who would become, for example, plumbers—or enter other fields that are well paid, necessary and unlikely to be replaced by automation in the near future.

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After reading Christof Koch's article on reviving the brain after death [“Is Death Reversible?”], I was struck by the similarities to the ideas found in Roald Dahl's short story “William and Mary.” It was first published in 1959 and describes a very similar method of keeping the brain alive by connecting the veins and arteries to it and running an artificial bloodlike solution through them. It obviously supports the idea that “death” occurs only when the brain dies and that the soul is contained within the brain. I find it interesting that Dahl had very similar ideas about reversing death 60 years ago and wonder if any of the researchers involved read the story.

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Koch appears to imply that Buddhists are reassured by an eternal cycle of reincarnation by citing it among other religious concepts as a “defense mechanism to deal with [the] foreknowledge” of death. But in Buddhism, this cycle, termed “samsara,” is laden with suffering and not reassuring at all. In fact, the journey of Buddhists is directed at releasing oneself from it.

Nashville, Tenn.

Koch repeatedly refers to death and lightly touches on its possible reversibility. Death is primarily defined as the irreversible loss of life, but do we know what life is? It is a property easy to recognize, difficult to describe and impossible to create in the laboratory. We suspect it originated in some earthly pond many millions of years ago, and it is only temporarily housed in all beings. Will science ever be able to restore a property whose nature we are unable to determine or even rationally discuss? And whatever life is, may it also be responsible for the push forward of evolution? This seems to be another intractable mystery.

JOAN GIL Professor emeritus of pathology, Icahn School of Medicine at Mount Sinai


“Is Death Reversible?” by Christof Koch, should have described modern fields such as machine learning as creating an illusion of understanding the “vegetative soul” rather than the “sensitive soul.” The vegetative soul defines the body's basic physical functions.