I Accept the Theory of Evolution
Embryology can be very helpful in showing how our evolutionary history appears during foetal development. There are a few quick and easy examples that spring to mind from all those available: gills, blood vessels, and kidneys.
In the early stages of development, fish embryos have a series of pouches (separated by grooves) near where the head will later develop. These are called the brachial arches - they develop into gills, and the grooves between them develop into the gill slits. It‘s very straightforward.
Other vertebrates have the same structures... including humans. In fact, I once had the opportunity to see these brachial arches for myself on a foetus, and it was fascinating. They‘re not ‘sort of like’ a fish‘s brachial arches... they [i]are[/i] a fish‘s brachial arches. They‘re morphologically completely identical.
Tiktaalik roseae, on the cusp between ocean and land, used gills and lungs, but after the move onto land, gills were superfluous (although Olympic swimming competitions would be very different had we retained them). Sometimes (it‘s very rare) the gill slits fail to close, but it‘s easily corrected via minor surgery once the infant is born.
Blood vessel development in fish is, once again, basic and straightforward, producing six major blood vessels. In mammals (including humans, of course), the same six major blood vessels appear in early foetal development, but then three of them disappear at the same time that our circulatory system stops resembling that of fish and instead becomes identical to the circulatory system of embryonic amphibians. Not similar... [i]identical[/i].
In amphibians, this system simply grows into an adult amphibian circulatory system, but in mammals (including humans, of course) it changes into the circulatory system of embryonic reptiles. Not similar to the circulatory system of embryonic reptiles... [i]identical[/i].
In reptiles, this system simply grows into an adult reptilian circulatory system, but in mammals (including humans, of course), it undergoes further changes (the development of carotid, pulmonary, and dorsal arteries) to become the mammalian circulatory system.
During development, human embryos form three distinctly different types kidneys... the pronephros, the mesonephros, and the metanephros. The first two systems are discarded. The pronephros is the kidney system found in fish and amphibians, the mesonephros is the kidney system found in reptiles, and the metanephros is the kidney system that we eventually use.
From fish to amphibian to reptile to mammal.
No matter how many comforting myths we mutter to ourselves, every foetus carries the truth.
In the early stages of development, fish embryos have a series of pouches (separated by grooves) near where the head will later develop. These are called the brachial arches - they develop into gills, and the grooves between them develop into the gill slits. It‘s very straightforward.
Other vertebrates have the same structures... including humans. In fact, I once had the opportunity to see these brachial arches for myself on a foetus, and it was fascinating. They‘re not ‘sort of like’ a fish‘s brachial arches... they [i]are[/i] a fish‘s brachial arches. They‘re morphologically completely identical.
Tiktaalik roseae, on the cusp between ocean and land, used gills and lungs, but after the move onto land, gills were superfluous (although Olympic swimming competitions would be very different had we retained them). Sometimes (it‘s very rare) the gill slits fail to close, but it‘s easily corrected via minor surgery once the infant is born.
Blood vessel development in fish is, once again, basic and straightforward, producing six major blood vessels. In mammals (including humans, of course), the same six major blood vessels appear in early foetal development, but then three of them disappear at the same time that our circulatory system stops resembling that of fish and instead becomes identical to the circulatory system of embryonic amphibians. Not similar... [i]identical[/i].
In amphibians, this system simply grows into an adult amphibian circulatory system, but in mammals (including humans, of course) it changes into the circulatory system of embryonic reptiles. Not similar to the circulatory system of embryonic reptiles... [i]identical[/i].
In reptiles, this system simply grows into an adult reptilian circulatory system, but in mammals (including humans, of course), it undergoes further changes (the development of carotid, pulmonary, and dorsal arteries) to become the mammalian circulatory system.
During development, human embryos form three distinctly different types kidneys... the pronephros, the mesonephros, and the metanephros. The first two systems are discarded. The pronephros is the kidney system found in fish and amphibians, the mesonephros is the kidney system found in reptiles, and the metanephros is the kidney system that we eventually use.
From fish to amphibian to reptile to mammal.
No matter how many comforting myths we mutter to ourselves, every foetus carries the truth.
56-60, F
