Carl Zimmer in The New York Times:
“Why are humans so smart?” is a question that fascinates scientists. Tadeusz Kawecki, an evolutionary biologist at the University of Fribourg, likes to turn around the question. “If it’s so great to be smart,” Dr. Kawecki asks, “why have most animals remained dumb?” Dr. Kawecki and like-minded scientists are trying to figure out why animals learn and why some have evolved to be better at learning than others. One reason for the difference, their research finds, is that being smart can be bad for an animal’s health.
Learning is remarkably widespread in the animal kingdom. Even the microscopic vinegar worm, Caenorhadits elegans, can learn, despite having just 302 neurons. It feeds on bacteria. But if it eats a disease-causing strain, it can become sick. The worms are not born with an innate aversion to the dangerous bacteria. They need time to learn to tell the difference and avoid becoming sick. Many insects are also good at learning. “People thought insects were little robots doing everything by instinct,” said Reuven Dukas, a biologist at McMaster University.