There’s Something Fishy About Your Ancestors
Grab a mirror or snap a selfie. About one percent of you will have a small dent close to your ear.
What you see in the photo (or in your mirror!) is evidence of the hundreds of millions of years-old story of life on earth.
A fish paleontologist seems an unlikely choice for chairman of the anatomy department at a prestigious medical school.
Meet Dr. Neil Shubin. He is host of the new PBS series Your Inner Fish and is author of a book by the same title. Dr. Shubin is witty and a talented story-teller (Your Inner Fish has been on my list of “favorite books I’ve read” for years). If you haven’t yet, watch episode one – I promise you’ll set the recorder for the rest. I love the Cosmos series, but Inner Fish is more engaging.
One Bone-Two Bones-Lots of Bones-Digits
All living things with skeletons – every reptile, every bird, every mammal, every human – every vertebrate alive today is descended from ancient fish. You might be surprised to learn how much of the human body is an inheritance from our fishy-families.
Every animal walking the planet today has the exact same grouping of bones in their limbs (think about your own arm or leg): one bone, two bones, lots of bones, digits.
We even see this arrangement in a preliminary form in the fins of fish.
In the transitional fossils between fish and the first amphibians, we see this pattern (one bone-two bones-lots of bones-digits) become more and more pronounced as we move closer to amphibians (the first true tetrapods, aka four-legged animals). The most famous of the fish-to-amphibian transitional animals, Tiktaalik, had a flat head and a neck.
Tiktaalik had distinctive fish features (scales, fins, gills), but inside its fins was an early version of one bone-two bones-lots of bones-digits. Tiktaalik even had a kind of wrist!
Your Inner Fish
Our skeletons are not the only key to our fishy past. In both human and fish embryos, there are swollen structures found near the face and neck. In fish, these structures become the gills. In humans, these structures become the lower jaw, the middle ear, and the voice box. That’s why a fish paleontologist is an excellent human anatomy professor – many of the same muscles, bones, and nerves humans use to talk and hear correspond to the gill structures in fish.
Sometimes your “inner fish” comes out.
If you have a tiny dent near your ear (sometimes it is a small tag), you have a remnant of the gill structures you had as an embryo. Own your inner fish!
Your Inner Boy Fish
In male fish, the testicles are located high up in the body – close to the heart. Fish are cold-blooded animals, so body temperature isn’t a problem for heat-sensitive sperm.
In male human embryos, testicles start in the same location – high up, tucked deep in the body. But humans are warm-blooded, so before birth (about 24 weeks old) the testicles of human males descend to a cooler climate outside the body cavity. This descent through the muscle wall leaves an opening where intestines can potentially poke through – a hernia.
Organizing Principle of Biology
The primary organizing principle of all modern biological sciences is the theory of evolution. Your Inner Fish is an excellent introduction as to why that is so.
Catch up here if you need to: Episode 1: Your Inner Fish
And get excited about the rest of the series! -Wednesdays on PBS.
(a) Goodnight (for the) Moon
Let’s hope for clear skies Monday night/early Tuesday morning (April 14-15). For the next two years, there will be a celestial rarity – a lunar eclipse every six months – and Monday night/Tuesday morning is the first one in the line-up.
The eclipse will begin at 1:58 a.m. (EDT, just after midnight on April 15); totality will be at 3:07 a.m. (EDT).
Lunar eclipses (unlike solar eclipses) are perfectly safe to view. During a lunar eclipse, the moon passes behind the earth so that the earth blocks the sunlight from shining directly on the moon.
As the moon starts to pass into the earth’s shadow, the round disc of the earth-outline becomes visible on the moon. Ancient Greeks saw this and understood that the earth was round.
As the sunlight passes though the earth’s dusty atmosphere, the light is bent (refracted) toward the red part of the color spectrum and cast upon the moon. The more dust in the atmosphere (from volcanoes, etc.), the redder the moon.
As the lunar eclipse progresses, the moon changes from its familiar white-gray color to a deep red, then back to white-gray.
And if a blood-red moon isn’t enough, look for Spica (a bright star in the Virgo constellation) right next to the moon. Then off to the west, look for Mars shining bright and orange.
I believe that the heavens declare the glory of God.
I believe that day after day the cosmos pours forth speech and night after night the cosmos reveals knowledge.
I trust that the evidence and knowledge that is revealed is true because the Creator of the cosmos is Truth.
very cool about the gill thing. my dad me, and my daughter all have those by the same ear.
Cool indeed! I’m always tempted to point it out when I see someone with… but it might be awkward!!
It definitely could be awkward