LIFE’S POSSIBILITIES
In “Life’s Big Bangs,” Asher Elbein reports on geochemist Abderrazak El Albani’s controversial argument that complex life emerged much earlier than thought and possibly did so multiple times, based on evidence from rock layers more than two billion years old. As David M. Ewalt kindly points out in “It’s Good to Be Wrong. Right?” [From the Editor], accepted facts in science have been proved wrong before, and Elbein’s idea is supported by recent discoveries from other researchers. Certainly in this age, when we have finally admitted that we do not have all the answers yet, we can at least embrace the further study of an idea that has reasonable hard facts that could lead to its possible acceptance.
We believe that Earth has had five mass extinction events because of the huge amount of evidence left behind. Yet how many others may have there been for which we have found no clues? If conditions had been close enough for more complex multicellular life to come into being earlier in Earth’s history, those same borderline conditions could have changed and wiped it out. We humans must remember that our perspective of time and possibility is incredibly limited. Mother Nature is very patient.
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SCOTT CLINE VIA E-MAIL
SUPPLEMENTAL INFO
In “Supplements That Fight Inflammation,” Lori Youmshajekian both provides a concise review of acute and chronic inflammation and explains that there is very little objective scientific evidence of benefit for the great majority of supplements marketed to “support immunity.” One of the three supplements she noted that actually can suppress inflammation, vitamin D, deserves special mention.
Vitamin D is a metabolic precursor of the hormone calcitriol. The classical role of calcitriol is to stimulate intestinal calcium absorption, but it also has established roles in innate immunity. Intracellular synthesis of calcitriol stimulates synthesis of bactericidal peptides by macrophages in infectious diseases such as tuberculosis. Calcitriol may also suppress some harmful immune responses in diseases such as multiple sclerosis and injury to pancreatic islets during the development of type 1 diabetes.
A fascinating feature of vitamin D is that it isn’t always obtained through diet. Ultraviolet B (UVB) rays in sunlight produce the D3 form of the vitamin in humans’ skin, as noted in “The Rise and Fall of Vitamin D,” by Christie Aschwanden [January 2024]. People with ample exposure to UVB light do not require any dietary vitamin D.
While the amount of supplemental vitamin D that people who get little or no UVB-containing sunlight need to optimally produce calcitriol when it is required remains a subject of debate, the VITAL (Vitamin D and Omega-3 Trial) studies noted in both articles demonstrated that vitamin D is not a drug and that vitamin D supplements don’t boost health in people who already have adequate levels of the vitamin (that is, those who already have a normal level of the vitamin D precursor 25-hydroxyvitamin D in their blood).
ARTHUR SANTORA WATCHUNG, N.J.
TELLING TIME
The clock puzzle “Find the Time,” by Heinrich Hemme [Advances], reminds me of a problem I set for my mathematically curious granddaughter many years ago. If you are given a clock with 12 at the top in which both hands are identical, you can sometimes read the time anyway. For example, if one hand points to 12, and the other points to 4, then the time must be four o’clock. If one hand points to 6, and the other points halfway between 10 and 11, then the time must be 10:30. Consider this: Can you always determine the time?
Dial orientation problems such as Hemme’s puzzle are related to this. Suppose that, on a dial that has no numbers and two equally sized hands, one hand points exactly right (to where a clock would usually indicate 3), and the other points exactly down (to where 6 would typically be). This would be impossible on a standard clock with 12 at the top. If the dial were rotated, however, so that 12 was to the right, then the time would be three o’clock. If 12 were at the bottom, then the time would be nine o’clock. Here are two questions to consider: Would this hand arrangement be possible if 12 were in any other position? And given any arbitrary hand arrangement, can you infer one or more possible positions for 12?
JOHN KNEISLY DELAWARE, OHIO
AIRBORNE AMPHIBIANS
“Graceful Flop,” by Rohini Subrahmanyam [Advances; April 2025], describes a study that found that cricket frogs do not truly skim over the water but instead perform a series of “belly flops” in which they sink for a fraction of a second and then jump out. The researchers posited that the frogs may do so because they need time to reposition their legs to power each jump. I’d like to suggest that the purposes of a cricket frog’s reimmersion may be more involved and elegant.
Lifting a body out of the water requires considerable energy. At the size of the cricket frog, even the energy to overcome surface tension is most probably, in my opinion, significant. Although cricket frogs, like all adult frogs, have lungs, these organs alone may not suffice to deliver enough energy for aerial acrobatics, especially because aquatic amphibians take in much of their oxygen through their moist skin.
Even with high relative humidity over a brief time, whooshing through the air may dry a frog’s skin enough to reduce oxygenation during behavior that has increased the need for it. Reimmersion between jumps replaces skin moisture. Moreover, the water at the shallow depths in which the cricket frogs sink is probably nearly saturated with oxygen both from surface absorption and from algae and other plants. So brief immersion may act as the froggy version of a gasp for air, also rewetting the skin to absorb atmospheric oxygen during the next jump.
DAN HEMENWAY VIA E-MAIL
ERRATA
In a “A New View of CO2,” by Lee Billings [Q&A December 2025], the illustration should have depicted carbon dioxide as a linear molecule.
“Flashes in the Night,” by Ann Finkbeiner [January 2026], should have said that China’s Einstein Probe began collecting data in mid-2024.
“The Imperiled Orcas of the Salish Sea,” by Kelso Harper [January 2026], incorrectly said that in 2008 Deborah Giles helped to develop an acoustic device used in orca research. She worked with colleagues to attach such devices to the backs of orcas that year.
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