What does your inner fish look like? Starting with a human arm a great anatomist, Sir Richard Owen, discovered that our arms, and legs, hands and feet fit into a larger scheme that is common pattern among other creatures such as bats, birds, frogs and lizards. The pattern that Owen discovered is one bone in the upper arm, two bones in the forearm, and nine little bones at the wrist, then a series of five rods that make the fingers. Seeing these similarities Owen went on to look at skulls and backbones here he found that there was a fundamental design in the skeleton of all animals which Owen credited to the Lana of a creator.
His findings were published in a monograph On the Nature of limbs (Subbing, 31-32). However it was Charles Darwin who supplied the reason why human arms and bat wings share common skeletal patterns, this being that they share a common ancestor. Yet, in fish the whole skeleton looks different. For instance, the base of a typical fin has four or more bones, but in the mid sass, the discovery of fish that had lungs in the Southern Continents started shedding some light on how fish crawled out of the water and started living on land. This confused anatomist so they named the fish
Ellipsoids Paradox, which means paradoxically scaled amphibian. Other fish were found in Africa and Australia, which were named lungfish. Perhaps what is most fascinating about these fish was that they had a single bone that attached to the shoulder much like the upper arm of a human. Anatomists had found a fish with a hummers bone. Around this same time there was the discovery of a fossil that was 380 million years old found on the shores of Gasps Peninsula in Quebec. This fish had a surprising mix of features seen in amphibians and fish. The fish was named Stenographer. This fossil had
Omen’s one bone, two bone pattern in its fin skeleton (33), making it another clue to humans ancient past. But, it was not until 2004 that Subbing and his colleagues found Tackling, a fish with a wrist, elbow and shoulder composed with the same pattern like humans arms. Tackling lived approximately 375 million years ago. Paleontologists say that Tackling represents a transition between non-trapped vertebrates (fish) such as Pantheists, known from fossils 380 million years old, and early teardrops such as Conestoga and Ichthyologist, known from fossils that are 365 million years old.
Tackling is a suture of primitive fish and derived trapped characteristics lead Subbing to characterize Tackling as a fishpond (Wilfred). In the PBS video Neil Subbing states, “Here we had the first fish who could do push ups. ” How did Tackling become so different from other fish? Another notable difference in Tackling is spiracles on the top of the head that suggest the creature had primitive lungs as well as gills. This may have led the development of a more robust ribcage, which is a key evolutionary trait of land living creatures.
This robust ribcage would have helped support Digitalis’s body any time it ventured outside the water. Yet another interesting difference was the fact that Tackling lacked bony plates in the gill area that restrict lateral head movement which makes Tackling the earliest known fish to have a neck with a pectoral griddle separate from the skull. Having a neck would have given Tackling a better ability to hunt prey either on land or in the shallows (Holmes). One hypothesis is that large shallow water fish lived in an environment that didn’t have much oxygen in the Water so they developed lungs. Dry Jenkins, who assisted in the interpretation of fossils said, ‘Fish feeding in water readily orient the mouth award food by maneuvering the entire body (Wilfred). This caused the first transition from water based life to land based life. However, if an animal spends any time out of water then it would need a true neck that would allow the head to move independently on the body. Thus Tackling is truly a transitional creature that exhibits changes that anticipate the emergence of land animals. Another very interesting discovery in the field of genetics was the Sonic hedgehog gene.
This gene is responsible for regulating trapped limb development. Every limbed animal has the Sonic hedgehog gene which s one of three proteins in the mammalian signaling pathway family called hedgehog. It plays a key role in regulating growth of digits on limbs and organization of the brain. The hedgehog gene was first identified in the fruit fly Drosophila melanomas in the classic Heidelberg screens of Christiana Insulin-Bollard and Eric Wiseacres, as published in 1980. These genes control the segmentation pattern of the Drosophila embryos.
If the hedgehog loses its function a mutation causes the embryos to be covered with identities, which are small pointy projections that resemble a hedgehog. That s how this got its name (Wiseacres). Then in 1 993, Philip Ingram, Andrew P. McMahon, and Clifford Tibia start some experiments to find a hedgehog gene equivalent in vertebrates. They ended up finding three homologous genes. Two of these were named after desert and Indian hedgehog species the third was named after Saga’s video game character Sonic the Hedgehog (Subbing 53). The Tibia group used chicken embryos to see how the Sonic Hedgehog worked.
They found that if they injected vitamin A at the site of Sonic Hedgehog that a mirror image of the wing would grow on top of the normal wing. Dan did the same kind of experiment on the fins of skates, which also showed a mirror image duplication (Dan). His findings show that Sonic hedgehog regulation may underlie major morphological changes during appendage evolution. If you look at the embryos of humans, chickens, and fish they are very similar. All of them have a head with gill arches. In the 1 8005 natural philosophers looked to embryos to try and find a common plan for life on earth.
One of these observers was Karl Ernst von Bare who studies chicken development. In the process he discovered that a chicken make look very different from a fish, but their embryos share striking similarities. Both develop from a single cell into tube- shaped bodies. They share many traits early on, such as a set of arching blood vessels in their necks. Fish keep this vessel arrangement but in chickens and humans, amphibians, reptiles this vessels are reworked into a different anatomy suited to getting oxygen through lungs (Developmental Similarities).
Yet another surprising thing that happens to the gill arches in mammals is they become the three middle ear bones known as the mallets, incurs, and stapes. The first arch is stapes and the second arch makes the mallets and NCSC. Karl Richter followed the gill arches of different species in 1837. He found that the two ear bones in mammals corresponded to pieces of the jaw in reptiles. Much later a German anatomist Ernst Gap in 1910-1912 provides more detail and interprets Erecter’s work in an evolutionary framework.
Embryologists and paleontologists didn’t started working together until 1 913 before that they worked in isolation. It was W. K. Gregory who saw an important link between Gap’s embryos and the African fossils found in the 1 sass. As Gregory looked at the successively more mammalian mammal like pitiless, he found a continuum of forms showing beyond doubt that over time the bones at the back of the reptilian jaw got smaller and smaller until they ultimately lay in the middle ear of mammals. So why would mammals need a three-boned middle ear?
It allows mammals to hear higher frequency sounds than animals with a single middle ear bone. This shift was accomplished by reposing existing bones not evolving new bones. So while there are many differences between fish and humans one can see our relationship to ancient fish ancestors if they look close enough. Through evolution we see how fins become limbs, aquatic life goes to land, and how structures have been repressed throughout life. Here in lies the proof that Darning’s Origin of the species gives a unique insight into our ancestry and answers the question why we look the way we do.