When people think about evolution, they often conjure up a mental picture that has humans branching off on the descendants-of-apes limb of the big animal-kingdom family tree. However, if you look further back in evolutionary history, you will see evidence that humans are also related to fish. That's right – fish! The evolution from fish to human was obviously a long, drawn-out process; however, the traits that humans inherited from fish show an uncanny resemblance in many instances.
If you're still wrapping your mind around the whole theory of evolution or are getting hung up on our simian brethren, prepare to have your mind blown by our aquatic ones.
The Way Your Face Forms Is The Same Way A Fish's Face Forms
Now, if you told someone that they look like they have a fish face, it would probably come off as an insult. However, everyone has a fish face to some degree. That's because a particular part of our faces is actually inherited directly from our fish ancestors. The "philtrum" is the groove located below your nose and above your top lip. This little patch of skin is largely ignored since it serves no purpose; however, it is a clue to where and how our faces formed.
Your face takes shape pretty early on in the womb, and it is the combination of three sections that come together in the fetus at the exact same time: your eyes have to come down and in, your jawbone and palate have to come up, and your nostrils and the middle part of your lip have to come down. The process is the same in fish fetuses, and the philtrum is the remaining leftover from all of this activity.
You Can Thank Fish For Your Ability To Speak
Many animals have the ability to make sound – using vocalizations to accomplish a wide variety of tasks, from finding a mate to warning trespassers to step off. Researchers have drawn parallels between human speech and certain mammalian ancestors, but far less research has been done to link human speech to underwater ancestors.
However, in 2008, Andrew Bass conducted a study that observed the neural circuitry responsible for vocalizations in toadfish. What Bass and his team found was that the neural pacemaker circuit responsible for making vocal sounds in these fish is very similar to the neural connections present in the vocal circuits of mammals. In other words, the studied toadfish had a collection of neurons at the base of their nascent brains that mirrored the collection of neurons that humans possess at the base of their brains. These neurons allow both of our species to make noises. Additionally, muscles, nerves, and bones that are vital to human speech are present in fish. Gill arches in fish have evolved over time into parts of the lower jaw and pharynx.
Human Embryos Are Basically Identical To Fish Embryos
All animals have in common the fact that they start out as a single cell. From that single cell, a worm forms, a penguin forms, a fly forms, a human forms, all developing into embryos that resemble the finished creature. Notably, fish embryos look a lot like human embryos. That's because fish body structures are the basis of human body structures. Both fish and human embryos have a head, a body, and a tail – although, obviously the tail disappears in humans.
Additionally, both embryos have gill arches in the neck region. In fish, these become gills. However, in humans, they morph into parts of the jaw, middle ear, and voice box.
Some Of The Bones That Allow You To Hear Came From Fish
Although, for a long time, scientists assumed that ears came with the evolutionary transition to land mammals, there's evidence to suggest that this feature, like so many others, came courtesy of our fish ancestors. There are two bones in the middle ear of humans (and other mammals) that are the same as two bones present in fish. In physiological terms, the quadrate and articular bones seen in fish correspond to the incus and malleus in humans.
In laymen's terms, this basically means that gill openings are the precursors to human ears. A structure called the hyomandibula in fish, which protruded into the gills, created a chamber where sound would later be amplified in mammals.
You Can Thank Your Fish Ancestors For Those Pesky Hiccups
The process of breathing in humans is controlled mainly by the brain stem. The brain stem sends signals to the primary breathing muscles in the human body, which cause them to contract. The brain stem is also responsible for the breathing processes of our underwater ancestors. In bony fish as well as sharks, the brain stem sends signals to the muscles surrounding the gills. Since the signals have to travel further in humans, they sometimes meet interference and ultimately cause a spasm.
The spasm will cue a quick inhale followed by swift closure of the epiglottis. This spasm is also what we experience as hiccups.
Fish Are To Blame For Hernias In Humans
Some fish – like sharks – have their reproductive organs in their thoracic cavity. In humans, these are also placed up near the liver during development, but they do not stay there. For females, these descend and become ovaries. In men, these descend further and become the testes. As the gonads travel all the way down to the scrotum in men, this weakens the abdominal wall and ultimately makes men more prone to hernias.
Inguinal hernias are when parts of the intestinal tissue get pushed through the abdominal wall. This is usually due to built up pressure from lifting things or straining. Fish, however, don't have this problem as their gonads stay up at their chests.