In the movie "WaterWorld," Kevin Costner's character has a mutation that gives him gills behind the ears. Is this really possible? Could a mutation allow people to swim in the water just like fish, without having to use any sort of scuba equipment?
One way to answer that question would be to look at evolution's record on the topic. Every time evolution has put a mammal in the water, whether it's a whale, a porpoise, a walrus or a manatee, evolution always does it with lungs rather than gills. Evolution often does drastic things to rearrange the rest of the body around the lungs -- for example, putting blowholes way back on top of the head in the case of whales, but evolution has never resorted to mammals with gills.
Why is that? The main reason lies in the fact that a mammal's gills would have to be gigantic. Gills work for fish because fish, being cold-blooded, don't need that much oxygen. A typical warm-blooded human being might require 15 times more oxygen per pound of body weight than a cold-blooded fish. When swimming, a human being would require even more oxygen than normal. Fish also use their mouths and gill flaps to move large amounts of water through their gills. Sharks and some other fish have to move constantly through the water so that enough water flows over their gills.
Think about how much of a fish's head is consumed by gills. Now imagine a human being with something like 15 times more room devoted to gills and some sort of system to force water over the gill surface. This is why you never see mammals with gills.
Watch this TED video featuring David Gallo, a leading ocean explorer, as he discusses some of the coolest underwater sea creatures. See how the shape-shifting cuttlefish works, as well as bioluminescent fish that can light up the ocean depths.
Oxygen from our gills would keep us from blacking out as we moved deeper, but below 200 meters or so we'd reach the bathyal zone, where it's dark and the water is 59 degrees Fahrenheit or colder [source: Britannica]. Living underwater
underwater
An underwater environment is a environment of, and immersed in, liquid water in a natural or artificial feature (called a body of water), such as an ocean, sea, lake, pond, reservoir, river, canal, or aquifer. Some characteristics of the underwater environment are universal, but many depend on the local situation.
https://en.wikipedia.org › wiki › Underwater_environment
Gills work for fish because fish, being cold-blooded, don't need that much oxygen. A typical warm-blooded human being might require 15 times more oxygen per pound of body weight than a cold-blooded fish. When swimming, a human being would require even more oxygen than normal.
Could humans have evolved with gills if we had spent most of our time in water? No. Oxygen levels in water are much lower than in air, and gills are not a very efficient means of extracting it. Gills couldn't provide the body with oxygen fast enough to support the high metabolic rate that we and other mammals have.
So humans cannot grow gills because they already have a respiratory system that is much more developed than aquatic animals and also being land inhabitants they do not require gills. Thus humans cannot grow gills.
If it wasn't for these adhesions that keep the lungs in place, an inverted sloth would spend up to 13 percent more energy on breathing. Lungfish have a unique respiratory system, having both gills and a lung. It is the only type of fish to have both organs, and there are only six known species around the world.
As a practical matter, it is unclear that a usable artificial gill could be created because of the large amount of oxygen a human would need extracted from the water.
To fly! The dream of man and flightless bird alike. Virtually impossible. To even begin to evolve in that direction, our species would need to be subject to some sort of selective pressure that would favour the development of proto-wings, which we're not.
We will likely live longer and become taller, as well as more lightly built. We'll probably be less aggressive and more agreeable, but have smaller brains. A bit like a golden retriever, we'll be friendly and jolly, but maybe not that interesting.
The evolutionary tree that led to humans means that if you go far enough back our ancestors had gills, but that far back they weren't humans they were the early tetrapods and before that fish. So while our ancestors had gills anything you would call human never had gills.
The next step is to prove that it can be used by humans, though Kamei believes that this will require a gill with a surface of 32 square meters (344 square feet).
Answer and Explanation: No, humans don't ever have gills, but during embryonic development the embryo does develop gill slits in the region of the neck. These pharyngeal slits develop into the bones of the inner year and jaw.
If humans also had gills then the deep sea divers could remain under sea water even without carrying oxygen cylinders for breathing as they would be able to extract the dissolved oxygen from water for breathing purpose just like a fish does.
Since acorn worms and the human lineage diverged 570 million years ago, pharyngeal slits for filtering food evolved into gills for extracting oxygen, and later into today's human upper and lower jaw and pharynx, which encompasses the thyroid gland, tongue, larynx (voice box) and various glands and muscles between the ...
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