If respect flows from Detwiler to John Hart, it also flows back to her. “Kate is one of the most inspired and creative collaborators we have worked with on our Congo projects,” Hart says. What great fortune, he adds, that the “widening ripples from those first encounters and experience with Africa, during our Watson years, have joined and been renewed in this collaboration.” Exactly what constitutes a new species has never been straightforward. This challenge is known as “the species problem,” and even Charles Darwin was equivocal about it, writing in The Origin of Species that “he was struck how entirely vague and arbitrary is the distinction between species and varieties.” Back when Detwiler was at Bates, the biological definition of species was, in very general terms, when “members of a group mate with members of that group” and produce fertile offspring. Hence the mule, the sterile offspring of horse and donkey, isn’t its own species. These days, says Detwiler, determining a new species is both art and, well, science, in that researchers consider and weigh a wide range of characteristics.
“It was really late at night, and I was looking at the screen thinking, ‘Oh my gosh, we’ve got the signal that we need from the genetics.’” Proving that the lesula was its own species presented special challenges. Known as guenons, the genus Cercopithecus features more than two dozen species that have a number of overlapping characteristics, such as similar diets, locomotion and arboreal living. In the end, Detwiler and her team would consider everything from the lesula’s genetics and behavior to the color of its butt (bright blue, by the way). “I said that we had to pick our criteria and move forward,” she recalls, “and argue that based on what we know today, we had what most biologists would call a new species.” Detwiler handled the genetic extractions and sequencing. She soon realized that at the genetic level, “we had something distinct” from the owlfaced monkey.
Terese Hart
Danny, a bushmeat buyer, with baby lesulas in Obenge. The researchers’ initial sightings of lesula were babies whose mothers had been killed for the bushmeat trade.
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Winter 2013