If you're like most people, the last time you threw a dance party you invited only humans, cockatoos, parrots, and parakeets.
Which makes perfect sense, because the only animals capable of keeping a beat, as far as anyone knew, were mimicking birds and (some) humans.
But new research suggests that for your next interspecies soirée, you might need to fill a kiddie pool and stock your fridge with herring, because it turns out that sea lions may also show a sense of rhythm.
Researchers at the Pinniped Cognition & Sensory Systems Laboratory at the University of California, Santa Cruz's Long Marine Laboratory, trained Ronan, a 4-year-old California sea lion, to bob her head in time with music. It is the first time a nonhuman mammal has been observed keeping a beat.
Before Ronan danced her way onto the scene, animal behaviorists were beginning to agree that keeping a beat – "rhythmic entrainment" in science-speak – was in some way a byproduct of neural adaptations that allow vocal mimicry. Inspired by popular YouTube videos of Snowball, a sulfur-crested cockatoo getting down to the Backstreet Boys' "Everybody" and Queen's "Another One Bites the Dust," researchers conducted an extensive search of the video database to find that every example of beat keeping, as far as they could tell, was done either by mimicking birds or humans. (It's mostly humans, actually. And most aren't very good.)
But Ronan changes all that. "The idea was that beat keeping is a fortuitous side effect of adaptations for vocal mimicry, which requires matching incoming auditory signals with outgoing vocal behavior," said lead researcher Peter Cook, in a university press release.
"It's understandable why that theory was attractive. But the fact is our sea lion has gotten really good at keeping the beat. Our finding represents a cautionary note for an idea that was really starting to take hold in the field of comparative psychology."
Now Ronan has a viral video of her own. Watch as she grooves to Earth, Wind & Fire's 1979 hit, "Boogie Wonderland," and then, later in the video, the Backstreet Boys' 1997 song, "Everybody." The researchers also trained Ronan to bob her head to Creedence Clearwater Revival's "Down on the Corner."
Ronan, notes Mr. Cook in the press release, actually stays on the beat better than birds who have been trained to do so. And he suspects that brain structures for keeping a beat might be widespread throughout the animal kingdom.
"Human musical ability may in fact have foundations that are shared with animals," Cook said. "People have assumed that animals lack these abilities. In some cases, people just hadn't looked."
Exactly what those brain structures are, however, is still anybody's guess. The paper says that Ronan's behavior is consistent with "some sort of neural oscillation mechanism with a preferred endogenous rate being driven by an external rhythm."
If that's the case, and if these mechanisms are present in humans as well, then Cook and his team may have helped figure out what, in the most literal sense, makes us tick.