Washington State University
Dr. Universe: Are mermaids real? Is there a species that contains DNA that’s half human and half fish? – Maite, 12, Texas
People have thought about mermaids for a long time. Ancient people even drew humans with fish tails on cave walls. So, did they really see mermaids or were they drawing from imagination?
The marine experts from the National Oceanic and Atmospheric Administration say that no mermaids have ever been found in the ocean.
But we’ve fully mapped only about one-quarter of the ocean floor. There are probably between 700,000 and 1 million different kinds of plants and animals in the ocean. At least two-thirds of those are still unknown to us.
Does that mean mermaids could be swimming around in parts of the ocean we haven’t explored? Maybe. But our best guess is that people mistook other sea animals for mermaids – like manatees and their relatives.
Manatees are also called sea cows. They’re big, slow swimmers that graze on sea grass. They belong to the scientific group Sirena – named after sirens. Those are killer mermaids. In Greek mythology, they lured people to their deaths with beautiful singing.
Like mermaids, manatees have bodies that taper into a tail. They have no hind limbs. Their front limbs are flippers with finger-like bones inside them. Manatees can turn their heads like humans do. Plus, their faces give a slight human vibe – but not quite like the mermaids we see in movies.
Maybe that’s why we have historical records of sailors saying they were surprised that the mermaids they saw weren’t as pretty as they expected.
When it comes to DNA, mermaids might be closer to home.
I talked about fish and human DNA with my friend Allison Coffin. She’s a neuroscientist at Washington State University.
“Fish and humans are distant cousins,” Coffin said. “Humans are actually more than half fish when you think about our genetic material. From that perspective, I guess you could say we’re all mermaids.”
The first ever animal with a backbone was a fish. So, all animals with backbones today came from fish who lived about 500 million years ago.
If you visit Coffin’s lab, you’ll see lots of zebrafish. They’re freshwater fish related to minnows. They have stripes a bit like a zebra. Zebrafish share more than 70% of their genes with humans. They have similar genes to 84% of the genes that cause human disease. That means scientists can study zebrafish to solve human problems.
Coffin studies sensory cells deep inside your ear called hair cells. Sound vibrations bend your hair cells. That sends electrical signals to your brain. Your brain uses the signals to figure out what it’s hearing and where the sound comes from.
Hair cells can be damaged by loud noise, injuries or just old age. That’s one way hearing loss happens.
Fish have hair cells in their ears, too. They also have them along the outside of their bodies. It’s a lot easier to study hair cells on the outside–which is one of the reasons scientists like Coffin study hearing in fish to help understand hearing in humans.
Unlike humans, fish can grow new hair cells if they need to. Maybe someday humans will be able to regrow their hair cells and regenerate their hearing, too.
All thanks to the hard work of scientists and the good luck that we have fish cousins.
Adults can help kids submit a question at askdruniverse.wsu.edu/ask