If you need a new icebreaker for your next dinner party, try this one: “Did you know your skull and head are organized like an extinct jawless fish?” OK That’s weird, but it is true.
Take your philtrum, for example. That’s the groovy indentation on your top lip beneath your nose.
You've probably never thought much about it, but your philtrum a clue to our shared ancestral past.
It is evidence of your "your inner fish,” as paleobiologist Neil Shubin called it in his book of the same name.
Shubin and colleagues discovered the fossil Tiktaalik, the so-called "fish with hands." The discovery has had implications for understanding human evolution. You see, it turns out, our origins are fishy.
And it's not just your philtrum. It's also your neck and many other structures.
The top lip, along with the jaw and palate, started life as gill-like structures on your neck. Our philtrum is a vestige of our evolutionary past, and of our time in utero.
As the human embryo develops, the parts of our face grow independently and then meet in the middle, at the philtrum, which forms a seam. The parts must line up in synchrony. When they don't, the result is a cleft palate.
Comparative embryology is a field of biology that compares the anatomical similarities and differences of animals in their earliest stages of development. The early human embryo looks very similar to the embryo of every other mammal, bird or amphibian—all of which evolved from fish.
Like all the fish in the sea we morphed. Our fins became hands, our tails disappeared and legs sprouted. Now we walk instead of swim. Well, most of us.
Yet we still have vestiges. If you've ever taken a bad fall backward, you know all about your coccyx, or tail bone.
But did you know the anatomy of the human inner ear with its three delicate bones is structurally related to the jaws of a shark?
Consider, also, your knees. Knee injuries are common among humans. The knees are one of our body plan's weakest joints.
That's probably because the first knee-like structures appeared 300 million years ago in the pelvic fins of fish. The animals that had them were mostly aquatic, so their so-called “knees” didn't bear much weight. It was just a simple hinge. And now this hinge must bear the entire weight of our heavy upright bodies as we run, walk, jump, play soccer and pursue sports unthinkable to a fish.
So, let’s take stock: You have an ear like a shark's jaw, knees like a fish—what else? Well, you hiccup like a tadpole. The hiccup reflex of tadpoles helps them breathe through their gills and prevents water from overwhelming their developing lungs.
If that sounds like something out of a science fiction movie, you’d be right. Minus the whole fiction thing.
To learn more about your inner fish, visit aqua.org/ablueview.