Even by yourself, you’re never alone, playing host to a multitude of organisms
Q. Of the 6,200 languages currently spoken as a mother tongue, the 16 with the most speakers account for fully half of the world population. To what extent are languages with few speakers being abandoned in favour of dominant ones? A. Economist David Clingingsmith collected and analyzed data from 15 countries covering 334 languages and found that only languages with fewer than 35,000 speakers are in decline (“The Economist Journal”). Some 4,300 languages (69% of the total) fall below this size, and Clingingsmith’s analysis suggests that about 1,700 will be extinct in 100 years — actually a smaller number than many scholars expected. Q. When entomologists talk about the “windshield phenomenon,” what are we to make of this? A. Older people in many countries remember the multitude of insect carcasses accumulating on car windshields during summer. Today, going by anecdotal evidence, drivers spend less time scraping and scrubbing, reports Gretchen Vogel in “Science” magazine. Now, the Krefeld Entomological Society has tracked insect abundance at more than 100 nature reserves in western Europe since the 1980s, noting dramatic declines of up to 80% at about a dozen of these sites.
And a study of stratified bird droppings in Canadian chimneys revealed a striking reduction in the fraction of beetle remains starting in the 1940s, around the time the pesticide DDT was introduced. After DDT was banned in the 1970s, the beetle fraction increased slightly but never returned to the original levels, and across North America and Europe, birds that eat flying insects are in steep decline.
Overall research suggests that declines in insect abundance and diversity are likely due to insecticides and habitat changes. As entomologist Martin Sorg says, “We won’t exterminate all insects…. That’s nonsense. Vertebrates would die out first. But we can cause massive damage to biodiversity — damage that harms us.” Q. Last night, while you were sleeping, legions of eight-legged creatures had an orgy between your eyebrows, even as other creatures inhabit your every crevice. Whoooa! What’s going on here? A. Think of yourself as a menagerie, populated by mites, arthropods, lice, and all manner of bacteria and fungi, says Daniel Cossins in ”New Scientist” magazine. Demodex mites, close relatives to ticks and spiders, are permanent and mostly harmless residents of the human face. In fact, says North Carolina State’s Megan Thoemmes, “Every person we’ve looked at, we’ve found evidence of face mites.” Only 0.4 millimeters long, they live buried head-down in hair follicles by day, then crawl out at night to copulate. “They have no anus, so on death disgorge a lifetime of feces into your pores.”
Some of these resident aliens are far from benign, such as parasitic worms like roundworm, hookworm and whipworm prevalent in the developing world; or hidden viruses such as “Herpes simplex,” which when activated are the source of cold sores.
But by far, the dominant group is bacteria, with cells perhaps more than 10 times the number of human cells, inhabiting “the caves of your nostrils and your anal-genital badlands and the crevices between your toes… The densest microbial gathering is in our gut, a community that affects aspects of health from digestion and immune defenses to possibly even mood and behavior.”
As Stanford University’s Justin Sonnenburg puts it, “Each of us is really a complex consortium of different organisms, one of which is human.”