Common descent has been proven to be the most parsimonious way to explain the connections that have and are still being found between seemingly unrelated organisms. In this essay, I will demonstrate that I have digested the entirety of Shubin’s book by convincing you that there is lineage that connects all vertebrates. To make this case, I will describe several connections seen within the fossils and genes of different animals. Many of these connections involve a common blueprint, modifications of which are seen across vertebrate species. These blueprints seen in both primitive and modern vertebrates serve as excellent evidence of descent from a common ancestor.
Shubin described Sir Richard Owen’s discovery of an underlying blueprint in the layout of limb bones in terrestrial animals, which he refers to as Owen’s one bone-two bones-lotsa blob-digits pattern. In humans for example, the humerus always articulates with the ulna and radius, followed by carpals which connect with the fingers. The difference in this blueprint across species is seen in the sizes and shapes of the bones. This recurrent pattern in vertebrate land animals can be explained by descent from a common ancestor that had limbs bones laid out in the same manner. It then follows that there should be a fossil of this common ancestor that indicates the transition between finned fishes and limbed amphibians. Not unexpectedly, Tiktaalik, a perfect intermediate was found in a rock of appropriate age. It has a flattened head, and a neck which is seen in land animals and the one bone-two bones-lotsa blob-digits pattern in its fins. It also has scales and webbed fins, which are characteristic of fish. By examining fossils and extant organisms such as zebra fish, lung fish,...
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...ity is easily explained by descent from a common ancestor.
In conclusion, I know it is safe to say the list of evidence for common descent continues given by Shubin continues. This ranges from similar blueprints in the embryonic development of the ears, to how different vertebrates make scents. Fossils and genes individually provide a good amount of evidence for an uninterrupted lineage, but together, the evidence has greater significance. One might wonder why it so important to prove descent from a common ancestor. For some, it might be just for satisfaction of the curious human nature but for others, it is much more. For example, practitioners of modern medicine will benefit immensely from an understanding of this history. Either way, the evidence is there, but everyone is free to choose what they do with it and how it affects (or doesn’t affect) their beliefs.
Over the last few hundred years, more and more has been added to the world’s fossil collection, fossils from all over the world. New theories have been created and old theories have almost been proven about the evolution of man. For example, we have proof that different species of man existed with certain types of DNA sequences and instincts, some we may not have anymore, or some that other species did not have back then. Even though it is subjected to much debate, one of the most widely accepted theories however, is that Homo sapiens interbred with the slightly more primitive species of man, the Neanderthal.
Wilford, J. (2004).Another Branch of Early Human Ancestors Is Reported by Scientists. [Online], March. Available at: http://gateway.proquest.com [Accessed 28 March 2004].
Web. The Web. The Web. 11 February 2014 “Biology: Evolution”. The New York Public Library Science Desk Reference.
In the book, Your Inner Fish, by Neil Shubin he presents the notion of evolution and how we can trace parts that make up the human body back to jellyfish, worms, and even fish. The book not only discusses how we arose to be what we are today, but also the implications our ancestors had on our current body plan. In this essay, I will demonstrate that I have digested the entirety of Shubin’s book by convincing you (dear reader) that everything in our bodies is based on simple changes to already existing systems. To make this case, I will use the evidence of limb development in a vast array of organisms, the four arches found in the embryological stage of development, the structures inside our noses, and how our ears have come about all due to modifications.
Rienzo, Anna Di. Wilson, Allan. 1991. Branching pattern in the evolutionary tree for human mitochondrial DNA. Evolution 88: 1597-1601.
As archeological discoveries of bone fragments and fossils continue to support the existence of homo-sapiens
The second of Tinbergen’s questions Phylogeny looks at the evolutionary explanations of development, as opposed to just how behaviour has adapted, including mutations in response to environmental changes. Some of these mutations remain in species even after necessity has gone, and can influence future characteristics of that species. The third of Tinbergen’s questions looks at Causation,...
Humans know or understand the theory of evolution and how they evolved from apes, but there is always talk of a missing link between apes and modern humans. Apes did not just suddenly evolve into modern day humans. Apes evolved into another species that fall into the relation of modern humans. This is what the missing link is referring to; we call the species hominins. Hominins comprised of many species actually, including but not limited to, Australopithecus afarensis and Homo erectus. Homo erectus may have been a direct descendant of modern Homo sapiens. These species hold strong evidence that they are the missing link between apes and modern humans. There are many pieces of evidence that lay the path of evolution from these species to modern humans, “…these include anatomy, living primate behavior, and genetic relationships” (Stanford, 237). Australopithecus afarensis comes first, existing about 3.9 to 2.9 million years ago, with intermediate anatomical traits between living apes and modern humans; their fossils were found in Africa (Yukimoto). About a million to two million years later, the species Homo erectus came into existence and lots of evidence has been found about this particular species, in fact, it was probable that it was the first species to leave Africa (Yukimoto). These species are significant in the evolution of modern humans. We do not have a clear path or even understand why these species emerged when they did or how they, in theory, eventually evolved into modern humans. We can only assume these things, by using various evolutionary processes such as natural selection, genetic bottleneck, and many more.
The origin of modern day whales, a mystery that has puzzled paleontologists for years, may have just been solved with the discovery of an ankle bone. This discovery might sound simple and unimportant, but the bones of these ancient animals hold many unanswered questions and provide solid proof of origin and behavior. The relationship between whales and other animals has proven to be difficult because whales are warm-blooded, like humans, yet they live in the sea. The fact that they are warm-blooded suggests that they are related to some type of land animal. However, the questions of exactly which animal, and how whales evolved from land to water, have remained unanswered until now.
From the ancient bones of the Neanderthals, scientists have been able to extract small amounts of DNA. The DNA comparisons to modern humans show no relationship, implying evolutionary separation (Kunzig, 159). Some anthropologists say the small sections of DNA found are not conclusive evidence, because modern humans show just as much variation in DNA. These people point out that individuals such as the “Portugal Kid” are hybrids of Neanderthals and modern humans, showing there was gene trading. One argument against this is that there is no skull from the ‘Portugal Kid” so it is hard to compare it to Neanderthals. Also, it is known that closely related species can breed and their offspring can be fertile, but they are still separate species (Kunzig, 161).
Scientists thought that interbreeding would be a logical assumption to the Neanderthal conundrum. Unfortunately, any evidence of DNA from Neanderthals mixed with human DNA is difficult to come by because their fossils are usually tarnished upon finding. That is until Svante Paabo, and his research team from the Max Planck Institute for Evolutionary Anthropology, came across the remains of twenty-four Neanderthals and forty early humans.* All of these fossils were nearly 40,000 years old and were from Germany, Russia, and Croatia. Nine of these fossils (four Neanderthal and five human)
Charles Darwin’s theory of natural selection explains the general laws by which any given species transforms into other varieties and species. Darwin extends the application of his theory to the entire hierarchy of classification and states that all forms of life have descended from one incredibly remote ancestor. The process of natural selection entails the divergence of character of specific varieties and the subsequent classification of once-related living forms as distinct entities on one or many levels of classification. The process occurs as a species varies slightly over the course of numerous generations. Through inheritance, natural selection preserves each variation that proves advantageous to that species in its present circumstances of living, which include its interaction with closely related species in the “struggle for existence” (Darwin 62).
The human archaeological record is a long and undefined story that may be the most complex question researched today. One of the big questions in human history is the disappearance of the Neanderthal people from the archaeological record around 30,000 BP. While for thousands of years Neanderthals and Anatomically modern humans crossed paths and perhaps lived in close relations, we have yet to really understand the degree to which they lived together. My hypothesis is that these two hominids, Neanderthals and Anatomically Modern Humans, interbred exchanging genes after Modern Humans dispersed from Africa and creating like cultures and material remains. The differences between Neanderthal and Modern humans are not only physical but also genetically evolved and this research will determine an estimated amount of admixture between the two groups.
He realized that snake embryos had bumps where there should be legs. Which mean they probably evolved from a creature with legs. He noticed that whale embryos had teeth, but adult whales did not have teeth. The most shocking of his embryotic studies involved human embryos. He noted that the human embryos as slits around the neck, the same in fish. The difference is that in fish the develop into gills, and in human the become the bones of the inner ear. This showed that humans must be descended from fish. This led him to the conclusion that all species were somehow connected. He theorized that beginning with a common ancestor, species had changed dramatically over generations. Some species may add new body features, or lose them. He called this descent with
...o happen. But with the help of fossil evidence we are able to identify common ancestors and evolutionary pathways between species. We also identify oxygen as a major key contribution for life to evolve. Also, through scientific research it has been established that arthropods and chordates have shared genes, leading to the path of vertebrates and human life.