Web edition: February 25, 2008
Print edition: March 1, 2008; Vol.173 #9 (p. 143)
Regarding "Whales Drink Sounds: Hearing may use an ancient path" (SN: 2/9/08, p. 84), I have heard that whales evolved millions of years ago into their present form, including their very large brains. We humans must be relatively recent in terms of our brain structures. Are there data concerning evolutionary development in whales?
"Learning to Listen: How some vertebrates evolved biological sonar" (SN: 5/14/05, p. 314) reviews the evolutionary steps in echolocation development in whales.Sid Perkins
Regarding "Pot Downer: Marijuana users risk gum disease" (SN: 2/9/08, p. 85), a familiar side effect of marijuana smoking is increased appetite, often for sweet foods. It is doubtful that the marijuana smokers immediately rush to brush their teeth after eating "munchies." If they smoke multiple times throughout a day, they may be constantly nibbling on sweets, leaving food lodged between teeth and gums, a fairly direct cause of gum disease.
Santa Cruz, Calif.
One result of such incessant munching would be plaque buildup. The researchers accounted for differences in plaque, as well as overall dental care, among the participants. These and other things being equal, pot smokers still had more periodontitis than people who didn't smoke the herb. Periodontitis starts out as gingivitis, marked by red, bleeding gums. When this inflammation results in the gums separating from the teeth and jawbone, that's periodontitis, which typically is irreversible. Gums receding from teeth make them look longer. This is often due to periodontitis in old age. Hence the term "long in the tooth."Nathan Seppa
Regarding "9/11 attacks stoked U.S. heart ailments" (SN: 1/26/08, p. 61): We must dissociate the attacks themselves from the intense media barrage that followed. Under the guise of providing information, the press seemed intent on inflaming our most negative feelings of fear, hatred, and grief. While the attacks were no doubt emotionally distressing, the psychological trauma was amplified a thousandfold by the nonstop and repetitive coverage.
Stephen E. Silver
Santa Fe, N.M.
Perkins, S. 2005. Learning to listen. Science News 167(May 14):314-316. Available at [Go to].