March 12, 2024: Today we dive into Daylight Saving Time debates, "sexual size dimorphism" data, and special glasses for viewing the April 8 total solar eclipse. —Robin Lloyd, Contributing Editor | | | It has long been assumed that in most species of mammals, males are larger than females. Now, an analysis of more than 400 mammalian species reveals that just 45 percent feature males that are larger than females, reports science journalist Rachel Nuwer. Nearly an equal number of species, 39 percent, have sexes that are about the same size, the researchers found. And in 16 percent of species, females are larger than males.
How they did it: Most past research on "sexual size dimorphism" in mammals looked at carnivores, primates and ungulates, the study's lead author Kaia Tombak found. She and her colleagues corrected this by adding data from each of 16 mammalian orders that contained at least 10 species each, groups that ranged from bats to rodents. The new study also added data on species from the order Eulipotyphla, which includes moles, shrews and hedgehogs.
What the experts say: "The questioning and reevaluation of prevailing assumptions about sex differences is part of an ongoing process that I call the female turn," says evolutionary biologist Malin Ah-King. "Perceptions about females have [changed] and are still changing away from passive, coy and mating with one male—and now, in mammals, being generally smaller than males." | | | Camargue horses Credit: USO/Getty Images | | | Many people have strong opinions about the clocks changing by an hour twice a year, but chronobiologists generally advocate for permanent Standard Time. Research shows it better aligns people's schedules with the sun year-round, reports journalist Teresa Carr. The biological clock rhythms of humans and other animals are entrained, or synchronized, to the solar clock. All of the researchers interviewed by Carr see potential harm in permanently setting our clocks an hour ahead because in the winter many people would have to start their day in darkness.
Why this matters: On the whole, the available data make a decent case that changing clocks to shift light from the morning to the evening could be bad for our health and safety. Some people struggle to sync their lives with their biological clocks, experiencing "social jet lag." That phenomenon is associated with smoking and consuming higher amounts of alcohol and caffeine as well as obesity, depression, higher risk for heart disease, and other ill health effects.
What the experts say: The focus on Daylight Saving Time overlooks harder questions about the built environment and how we choose to live and work, says sleep researcher Derk-Jan Dijk. "The more general question is how the heck do we actually come up with work schedules and social schedules, which basically determine to what extent we make use of natural light versus man-made light?" |  | Commuters walk through the morning bright sunlight coming from the 60 feet (18m) high windows in Grand Central Terminal in New York City on March 11, 2019 the first morning after Daylight Savings Time took effect March 10, 2019. Credit: Timothy A. Clary/AFP via Getty Images | | | • An expansion of Medicaid, the state and federal insurance program, has been hailed as a way to prevent overdoses from illicit opioids and other drugs. Health insurance can help tackle the overdose crisis because it allows people to afford substance use disorder treatment. But expansion of Medicaid is an insufficient solution to the problem, write substance use disorders researcher Hannah Cooper and her colleagues. The team's recent analysis of all overdose deaths in the U.S. from 2008 to 2018 found that Medicaid expansion did not prevent fatal overdoses among people facing poverty. In digging deeper, the researchers found that a shortage of treatment slots posed a barrier even for people with insurance who sought treatment. And in 2020, only 71 percent of treatment facilities nationwide accepted Medicaid. Low reimbursement rates for methadone treatment also serve to inhibit access to this health care. "We must bolster treatment to meet demand, expand program and provider acceptance of Medicaid, and permanently relax oppressive methadone policies before another million lives are lost," the authors write. | 5 min read | | | Total solar eclipse-viewing plans are a popular topic of conversation these days. I've heard people mention Upstate New York, Cleveland, Ohio, Houston, and Austin, Texas as viewing destinations along the 115-mile-wide band of the April 8 total solar eclipse. (Even if you can't visit the path of totality, you can see a partial eclipse from anywhere in the Lower 48 states and much of Mexico and Canada.) If you are lucky enough to have planned ahead or to find an impromptu viewing destination that is not in gridlock on the big day, here is a guide to using extra-dark eclipse glasses. The essay includes a list of safe solar viewer and filter suppliers vetted by the American Astronomical Society. For more details on everything from the influence of solar eclipses on science to the best places to view the event, check out Scientific American's full report on the Total Solar Eclipse of 2024.
| —Robin Lloyd, Contributing Editor | | Subscribe to this and all of our newsletters . | | | | Scientific American
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