"Dogs' understanding of human forms of communication is something new that has evolved," Kaminski said, "something that's developed in them because of their long association with humans." Although Kaminski has not yet tested wolves, she doubts they have this language skill. "Maybe these collies are especially good at it because they're working dogs and highly motivated, and in their traditional herding jobs, they must listen very closely to their owners."

Scientists think that dogs were domesticated about 15,000 years ago, a relatively short time in which to evolve language skills. But how similar are these skills to those of humans? For abstract thinking, we employ symbols, letting one thing stand for another. Kaminski and Tempelmann were testing whether dogs can do this too.

Betsy's owner—whose pseudonym is Schaefer—summoned Betsy, who obediently stretched out at Schaefer's feet, eyes fixed on her face. Whenever Schaefer spoke, Betsy attentively cocked her head from side to side.

Kaminski handed Schaefer a stack of color photographs and asked her to choose one. Each image depicted a dog's toy against a white background—toys Betsy had never seen before. They weren't actual toys; they were only images of toys. Could Betsy connect a two-dimensional picture to a three-dimensional object?

Schaefer held up a picture of a fuzzy, rainbow-colored Frisbee and urged Betsy to find it. Betsy studied the photograph and Schaefer's face, then ran into the kitchen, where the Frisbee was placed among three other toys and photographs of each toy. Betsy brought either the Frisbee or the photograph of the Frisbee to Schaefer every time.

"It wouldn't have been wrong if she'd just brought the photograph," Kaminski said. "But I think Betsy can use a picture, without a name, to find an object. Still, it will take many more tests to prove this."

Even then, Kaminski is unsure that other scientists will ever accept her discovery because Betsy's abstract skill, as minor as it may seem to us, may tread all too closely to human thinking.

Still, we remain the inventive species. No other animal has built skyscrapers, written sonnets, or made a computer. Yet animal researchers say that creativity, like other forms of intelligence, did not simply spring from nothingness. It, too, has evolved.

"People were surprised to discover that chimpanzees make tools," said Alex Kacelnik, a behavioral ecologist at Oxford University, referring to the straws and sticks chimpanzees shape to pull termites from their nests. "But people also thought, 'Well, they share our ancestry—of course they're smart.' Now we're finding these kinds of exceptional behaviors in some species of birds. But we don't have a recently shared ancestry with birds. Their evolutionary history is very different; our last common ancestor with all birds was a reptile that lived over 300 million years ago.

"This is not trivial," Kacelnik continued. "It means that evolution can invent similar forms of advanced intelligence more than once—that it's not something reserved only for primates or mammals."

Kacelnik and his colleagues are studying one of these smart species, the New Caledonian crow, which lives in the forests of that Pacific island. New Caledonian crows are among the most skilled of tool-making and tool-using birds, forming probes and hooks from sticks and leaf stems to poke into the crowns of the palm trees, where fat grubs hide. Since these birds, like chimpanzees, make and use tools, researchers can look for similarities in the evolutionary processes that shaped their brains. Something about the environments of both species favored the evolution of tool-making neural powers.