Dogs may bark to music and chimps may bang on drums, but creatures that can truly keep a beat are rare, raising intriguing questions about the evolution of the human brain.

A bonobo named Kanzi first surprised researcher Patricia Gray more than a decade ago, when Gray was absent-mindedly tapping on a glass window and the great ape on the other side tapped back.

Startled, Gray decided to speed up the tapping and the Kanzi kept pace, even reclining on his back to tap with his toes when treated to a sprig of green onions for a snack.

"So I thought we should be taking a look here at temporal dynamics as a way of getting to some very interesting questions," said Gray.

Since then, a few other creatures have showed scientists that they can truly synchronize their movements to a musical beat -- among them a cockatoo that is moved by listening to the Backstreet Boys and a sea lion named Ronan whose favorite song turns out to be the Earth, Wind and Fire classic, "Boogie Wonderland."

While animals in circuses and at water parks may appear to dance or sway to pop music blaring from speakers, most of the time they are not truly synching their movements to the beat, researchers told the American Association for the Advancement of Science meeting on Saturday.

"Is it just something that we and a couple of other species do?" asked Aniruddh Patel, professor in the department of psychology at Tufts University.

"This is an important question," said Patel, whose latest research paper in the journal PLoS Biology is entitled: "The evolutionary biology of musical rhythm: was Darwin wrong?"

- Do animals do rhythm? -

Charles Darwin believed that all creatures perceived and enjoyed musical cadences, and that rhythm was likely common to all animals, but that its expression depended on how complex they were.

But as scientists look more closely at true beat-keeping, and learn more about the relationship between rhythm and other abilities like language, some believe Darwin may have been mistaken.

"In terms of cognition, in humans the ability to move to a beat seems to be related to other cognitive capacities," Patel said.

Some studies on humans have shown that youths with better verbal skills are also better at keeping a beat.

But many mysteries remain, including whether this ability is innate or can be learned.

The bonobos Gray worked with were able to understand rhythm and timing, and after being given drums of their own they were soon jamming with the likes of Peter Gabriel.

The apes liked to beat the drums, but are not as precise in their movements as the cockatoo.

"Maybe we ought to think of bonobos more like human children than human adults," said scientist Edward Large of the University of Connecticut.

"Infants will move more to the music than to speech but they don't synchronize. As children get older, to the ages of two, three, four, they still don't synchronize," he added.

When toddlers get closest to truly keeping a beat is when they are in a playgroup with other people, studies have shown.

"They really do best in the context of a social interaction," Large told reporters.

"Somehow rhythm is about interacting with other people."

- A 'Type A' sea lion -

For the sea lion, Ronan, who was trained for more than a year by researchers at the University of California, Santa Cruz, hard work and a "Type A" personality paid off, said scientist Peter Cook.

"She was maybe an extra smart sea lion and she was very motivated to work so she eventually figured it out," Cook said.

"But it wasn't through social interaction," he added.

Ronan's success at nodding her head to music has also upended the notion that an animal must have the capability for vocal mimicry -- a basic verbal skill which sea lions do not possess -- in order to keep a beat.

For Large, whose focus is on brain rhythms, the intrigue lies in how networks of the brain coordinate with each other by synchronizing rhythms, and how brain rhythms can synchronize with musical rhythms.

"Synchrony, I think of as more of a building block that evolution has in its toolkit, and using it one way or another depending on the species and the situation."