It is clear that fossils are great evidence of evolution. Coyne not only devotes an entire chapter to them, but also states that “within these petrified remains lies the history of life”(7). By following the fossil records, it is easy to see how a specific organism changed slowly over time into an organism we see today. By watching the species change, it is easy to see that the final organism clearly evolved and was not created and placed onto the earth.
That being said, imagine you are a scientist with the fossil records conveniently in hand. Your job is to explain to someone why evolution is true quickly. Because time is money, you can only pick one species’ line of fossils to prove to the ignorant one that evolution is true. Which line of fossils would you choose? Which species’ ancestry most completely proves evolution? Explain using how complete that specific line of fossils is (are there missing links?), how much change that species underwent, and if we can see evidence of that species’ relatives on that organism today(bone structure, teeth, ect.).
If I were to choose an ancestral line to prove evolution, I would choose the birds ancestral line. This is because the evolution of saurischian theropods into primitive birds is both well known and comparatively well documented, and genuses such as [i]Archaeopteryx[/i] and [i]Velociraptor[/i] are more well known than index fossil molluscs or brachiopods, which also show significant change over time.
ReplyDelete[i]Archaeopteryx[/i] is a primary example used in explaining the evolution of theropods into birds. Found in the Jurassic period, fossils of [i]Archaeopteryx[/i] have traits of both theropods and birds. Bird like features include the development of a wishbone and development of flight feathers. Reptilian features include teeth and a bony tail supported by vertebrate. These shared features indicate that [i]Archaeopteryx[/i] are very likely a result of the gradual evolution of theropods into birds.
[i]Velociraptor[/i] adds to the evidence of the shift from theropods to birds because recent discoveries indicate that [i]Velociraptors[/i] possess feather-like structures. These feather-like structures were likely to be used in thermoregulation in the form of insulation (Campbell 864).Though [i]Velociraptor[/i] did not evolve until the Cretaceous Period, feather-like structures indicate that there is likely a species that split between the lines of [i]Archaeopteryx[/i] and [Velociraptor[/i] that also possessed feather-like structures. This relates to the theme of change and continuity, as though [i]Archaeopteryx[/i] and [i]Velocirapter[/i] changed to fit different niches, their possession of feather-like structures were preserved from their common ancestor.
for some reason, the page did not read my [i][/i] tags. Those are supposed to italicize text.
ReplyDeleteI am in agreement with Ray that the evolutionary line birds would be the most successful in convincing someone that evolution is true. Not only do fossils show the evolution from reptiles to birds, but there also is important evidence for the theory of evolution in the evolution of flightless birds. The evolution of birds from reptiles, like Ray said, is well documented, and Coyne makes some very good points regarding vestigial elements and flightless birds.
ReplyDeleteFossil evidence suggests that modern birds evolved form theropods, which, as of 200 million years ago, were nothing like birds. The transitional species from these theropods to birds is Archaeopteryx lithographica; that species has numerous structures that suggest that the species was a “mosaic”(Coyne 42).That is, the species has mostly reptilian structures but has a few bits that are birdlike. Archaeopteryx lithographica had feathers and an opposable big toe, which are both birdlike features. The evolutionary line continues with Sinornithosaurus millenii, which had long feathers covering its entire body, but also had reptilian features like claws, teeth, tongue. The line continues with Microraptor Gui, which was significant because it had feathered arms and legs. These common structures between birds and reptiles are strong evidence in support of the theory that birds evolved from reptiles. However, in my opinion, the most convincing fossils in this evolutionary chain(and fossils that Ray didn’t mention) are the Mei long and an unidentified species who died while brooding. The Mei long fossil is extremely important because it shows a behavioral link between ancient fossils and modern birds. Mei long was found in a sleeping position which, as figure 11 page 45 shows, is strikingly similar to that of modern birds. The other behavioral link that Coyne mentions is unnamed, but was found in the brooding position, which is a common behavior for birds. This relates to our own study of behavior in the first unit of the year, where we discussed how behavior and anatomy/physiology are very closely related. Animal behavior is controlled by natural selection; simply put, animals behave in the manner that allows them to survive and reproduce (Campbell 1120). Therefore, the fossils that suggest a behavioral link between fossils with both bird and reptile features and modern birds would be very helpful in convincing an ignorant person that evolution is true. In the case of birds, behavioral and structural similarities of modern birds to these ancient fossils support evolution.
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ReplyDeleteHowever, if the ignorant person I’m convincing happens to be creationist, then he or she will probably dismiss any fossil evidence given that they believe the earth was created only a few thousand years ago. The existence of vestigial elements(in this case, wings in flightless birds) help prove evolution and disprove creationism as well, and is even within the supposed ten thousand year time span that the earth has been around according to creationists. While this argument doesn’t necessarily involve fossils, it involves extinct species of birds, which are still part of the bird ancestral line, even though these extinct species(such as dodo birds) are much more recent than the fossils mentioned above. Vestigial elements are structures that, because of evolution, are no longer used for their original purpose. Flightless birds still have wings, but those wings aren’t used for their original purpose, which is flight. Wings in birds like ostriches still have functions like balance. These elements help disprove creationism because, if a creator created all of these birds from scratch, there would be no need to even give them wings in the first place(Coyne 58). The better explanation as for why birds lost there wings is wings weren’t exactly an advantage for some birds in certain environments. For example, on islands, there aren’t many predators that birds would need to fly to avoid, and food is often found on the ground, so wings would be an unnecessary hindrance. This evolutionary process relates to the biological theme of continuity and change because some birds evolved into flightless birds while birds in other environments(like non-island areas with trees and predators) still can fly. The fact that some birds changed because of environmental factors while others stayed the same suggests is important in an explanation of evolution.
Overall, the birds ancestral line would be best in showing how evolution is true. Both the fossils and later parts of the ancestral line of modern birds have myriad evidence as to how and why birds(and other animals) evolve.