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Meditations on meditation

People get uncomfortable when they’re left alone with their thoughts. In fact, as Bruce Bower reported in “People find solitude distressing” (SN: 8/9/14, p. 12), college students willingly gave themselves electric shocks to avoid quiet contemplation.

Readers chimed in with lots of explanations for the findings. Nancy Martsch wondered about family dynamics. “As an only child, I’ve noticed that people from large families or with very close siblings tend to depend on the company of others for entertainment.” John Day asked, “Why would the authors imagine even for a millisecond that the pathological behavior of modern Americans is a result of Darwinian evolution, as opposed to a reaction and plastic adaptation to a crazy-paced, out-of-control civilization?”

Gretchen Dean warned against using the study to make sweeping generalizations about human behavior. “Perhaps a statement attributed to the French philosopher Pascal should be considered: ‘The trouble with Western man is he does not know how to be content in an empty room.’ Maybe the study simply lends validity to this observation and does not apply to all human minds.  Culture can influence far more than just dress and customs. Before declaring a behavior universal, perhaps researchers should take it on the road.”

Tracing Tibetans’ genetic past

Tibetans may have gained a genetic adaptation for high-altitude living from extinct human relatives known as the Denisovans. Analyses show a match between distinctive DNA variations in both groups, wrote Tina Hesman Saey in “Tibetan high life aided by old DNA” (SN: 8/9/14, p. 8).  

Jim LeSire wasn’t convinced that the Denisovans were the source of the variations. “I see no reason why it should be necessary for Tibetans to have inherited their genes from the Denisovans; they could just as easily have developed their own.” Tim Cliffe countered that the gene variants weren’t just similar; they were an exact match. “That doesn’t happen by accident or coincidence.” Even if the variants are virtually the same, LeSire argued, “no one knows where either group got it. The Denisovans might have inherited it from the same source as the Tibetans.”

Both readers have a point, says Saey. “Tibetans and Denisovans could have inherited the adaptation from an unknown extinct hominid group — the researchers can’t rule out that possibility. But the exact match is what makes it seem unlikely that Tibetans and Denisovans acquired so many identical DNA mutations independently.”

The Sahara’s less-dusty interludes

In “Dust helped build up the Bahamas” (SN: 8/9/14, p. 18), Thomas Sumner explained how airborne particles from the Sahara Desert may have provided nutrients to the carbonate-producing microbes that erected the islands.

But the Sahara hasn’t always been a desert, as John Compton pointed out. “Did dust continue to blow across the Atlantic during the ice ages to promote the growth of the calcium carbonate layer, or was this an intermittent process, depending upon the climate?”

Geochemist Peter Swart of the University of Miami in Florida replies that while the desert was periodically less arid or less extensive than it is now, it’s likely that some dust was always blowing across the Atlantic from the Sahara and nearby regions. During less-dusty periods, Swart notes, the Bahamas’ growth would have slowed.

Corrections

The right-hand graph in “Dead zone shrank as winds declined” (SN: 9/6/14, p. 11) shows a repeated number. The second barometric pressure from the top should be 200 pascals, not 250 pascals.

Due to an editing error, words were omitted from “Gene methylation can lead to cancer” (SN: 9/6/14, p. 15). The sentence should read: “Lanlan Shen of Baylor College of Medicine in Houston and colleagues studied whether cancer could result from attaching a chemical tag called a methyl group to the DNA building block cytosine.”