Claudia Wallis's account of how her opinion regarding treatment options for osteoporosis has changed in “A Perfectly Avoidable Crisis” [The Science of Health] was interesting. But I was disappointed that she did not back up her claim that “new drugs have emerged that do not have the same risks” of osteonecrosis of the jaw and atypical femoral fracture that oral bisphosphonates do. I would have appreciated knowing the names of those drugs and at least a little something about the research that suggests their greater safety. I'm sure that rather than accepting even a small risk of devastating side effects, most women with osteoporosis would opt for a “risk-free” treatment—if such a thing existed—or even one with side effects that are less potentially severe.

Scottsdale, Ariz.

WALLIS REPLIES: Hutchison Bernard raises an important question that I didn't have room to address. Not every drug for osteoporosis carries these specific risks. Some work by a different mechanism than the bisphosphonates and have a different profile of side effects. Teriparatide and abaloparatide, for instance, are injectables that appear to build bone rather than just slowing bone turnover. But they, too, involve certain risks. Moreover, patients who take them are usually switched over to bisphosphonates after 18 to 24 months to maintain bone density. For some patients, hormone replacement therapy or the related drug raloxifene are good options, although they have risks as well. Bottom line: treatment for osteoporosis should be tailored to the individual patient, based on a careful evaluation and discussion with an endocrinologist or another specialist.


In “The Means of Reproduction,” Karen Weintraub discusses fertility research on converting blood or skin cells into viable sperm and eggs. She states that Marcy Darnovsky of the Center for Genetics and Society “does not think that lab-generated germ cells could ever be safe enough to justify their risks” and quotes her as saying this is because “it's likely to be extremely biologically risky for any resulting children.” Darnovsky then notes that many cloned mammalian embryos fail to develop and that some have been born with birth defects.

But embryos frequently fail to develop in regular reproduction, and children are born with health problems in regular reproduction as well. The question is not whether a system in which blood or skin cells are used in place of sperm or eggs can be perfect but whether it can be better than the alternative. At some point, it might even be safer than regular reproduction by eliminating birth defects such as Down syndrome. People might even someday blame parents who choose traditional reproduction over the safer scientific methods for carelessly subjecting their children to greater risk.

Williston, Vt.


In “Island of Heavyweights,” Christoph E. Düllmann and Michael Block discuss efforts to create superheavy elements that would last for minutes or longer before decaying, forming an “island of stability” on the periodic table.

I would think superheavy isotopes near the island of stability would be created by neutron star collisions, which excel at creating heavy, neutron-rich isotopes. Might superheavy elements be detectable in the debris of neutron star collisions, such as the one seen last year? Was uranium detected or inferred in that collision's debris?

San Jose, Calif.

DÜLLMANN REPLIES: The question of whether superheavy elements are formed in processes occurring in nature is among the most interesting aspects of the field and has not yet been conclusively answered. An open question is how the heaviest nuclei created in astrophysical phenomena decay. If they decay by spontaneous fission—that is, by disintegrating into two lighter fragments—access to very long-lived nuclei at or near the center of the island of stability is blocked. If, on the other hand, they are stable enough against spontaneous fission that other decay modes, such as beta decay, dominate, a pathway to the island may be available. Hence, studying the nuclear structure and stability of the heaviest elements is an important part of superheavy element research. Of special interest are the most neutron-rich nuclei, as astrophysical events proceed in neutron-rich environments.

As for the recently observed neutron star collision: individual elements were not identified. The detected optical signature is best explained by the formation of very heavy elements, but scientists did not measure an observable tied specifically to uranium.


Andrea Gawrylewski's review of The Wizard and the Prophet, by Charles C. Mann [Recommended], misrepresents Norman Borlaug, who helped to bring about the green revolution, as thinking “technology would find a way to save us.”

Borlaug was well aware that the green revolution didn't address the root of the problem. In the lecture he gave when he received the Nobel Peace Prize in 1970, he said, “The green revolution has won a temporary success in man's war against hunger and deprivation.... If fully implemented, the revolution can provide sufficient food for sustenance during the next three decades. But the frightening power of human reproduction must also be curbed; otherwise the success of the green revolution will be ephemeral only.” He therefore saw the green revolution simply as a stopgap while humanity, he hoped, got its act together on the real problem.

Stroud, England


In “Alvy's Error and the Meaning of Life” [Skeptic, February 2018], Michael Shermer makes his own teleological error by ascribing design to evolution: “We are sentient beings designed by evolution to survive and flourish in the teeth of entropy and death.” There is no plan in the unfolding of evolution, but there is great mystery in carbon becoming aware of the universe and using words to describe its grandeur.

Dallas, Tex.

SHERMER REPLIES: Wade is correct in the sense of top-down goal-directed evolution, but Charles Darwin's genius was to show how evolution can produce the illusion of top-down design from the bottom-up process of natural selection. Functional adaptations are “designed” features of nature: wings are designed to fly; eyes are designed to see. Carbon atoms are not aware of anything. But when combined to help build complex protein chains that form cells, some of which are neurons that generate thoughts in brains, awareness of the cosmos and even self-awareness are possible, given time. It would seem that 4.6 billion years is sufficient, at least on this planet. The next big discovery will be where else this has happened in the cosmos.


“Quick Hits,” by Yasemin Saplakoglu [Advances], incorrectly referred to ticks as insects. They are arachnids.