A sea lion at the Wildlife Conservation Society New York Aquarium, making fun of humans' breath-holding abilities (Photo: Getty)
They might not have opposable thumbs, but marine mammals definitely have us beat when it comes to holding their breath.
The longest a person has ever stayed underwater without a breathing apparatus is 22 minutes and 22 seconds - a record set last year by German diver Tom Sietas. But most of us can only stay down there for a couple of minutes.
For marine mammals like whales and sea lions, storing air and staying underwater comes naturally: a sperm whale can remain underwater without breathing for up to two hours, with most of their dives lasting an average of 45 minutes.
Until now, scientists didn't know exactly how marine species could hold their breath for so long, but new research has provided an answer: and it all started with looking at muscles.
Human muscles are red - that's because of a protein called myoglobin, which allows our muscles to store oxygen.
In marine mammals, the muscles are almost black because they contain so much myoblobin.
Here's how that helps them stay underwater: the myoglobin molecules have a strong electrical charge, and they repel each other (kind of like the poles of two similarly charged magnets).
This prevents the proteins from sticking together, allowing for a much higher concentration of myoglobin, which means they can store a lot more oxygen in their muscles.
A tail of a whale (Photo: Getty)
The discovery offers a cool insight into our mammalian cousins and helps scientists understand how mammals have evolved over the years.
The researchers traced the muscle oxygen stores in more than 100 mammalian species and their fossil ancestors.
"We really are excited by this new find, because it allows us to align the anatomical changes that occurred during the land-to-water transitions of mammals with their actual physiological diving capacity," Scott Mirceta, one of the researchers, said in a news release.
The research could also help us better understand human diseases that involve proteins sticking together, such as Alzheimer's and diabetes. And it could aid in the development of artificial blood substitutes.