The authors base their conclusion on a close physical resemblance between orangutans and humans, which they say has been overshadowed by genetic evidence linking us to chimps.

What's more, the study authors argue, the genetic evidence itself is flawed. (Get a genetics overview.)

John Grehan, of the Buffalo Museum of Science in New York State, and Jeffrey Schwartz, of the University of Pittsburgh in Pennsylvania, say that the DNA evidence cited by many scientists only looks at a small percentage of the human and chimp genomes.

What's more, the genetic similarities likely include many ancient DNA traits that are shared across a much broader group of animals.

By contrast, humans share at least 28 unique physical characteristics with orangutans but only 2 with