Darwin brings up many arguments for evolution. One of the major ones is found in the bodies of humans and animals. Darwin believes that all animals come from one ancestor. He explains that many of our ones are very similar. He also says that there are many characteristics that are useless. They may have been useful in the past, but through time have become unnecessary. Additionally, he talks about many animal embryos being similar (Darwin, 499-502). Darwin uses these arguments to show evidence of us coming from one ancestor and that differing structures are developed or stop being of use through natural selection. Moreover, he explains that patterns of migration are evidence of animals changing throughout time. He explains that bats that can cross the ocean would live on islands. This provides evidence that differing geological environments have decided how animals have evolved (Darwin, 484-499).
I think the most convincing thing about his document are his arguments about animals changing due to natural selection specifically the ones listed above. I found it interesting that he talks about a single ancestor and biological similarity in vestigial structures. I think I found his counterargument to fossilization is the least convincing part of his document. He talks about there being imperfection in the geological record. He says that only some classes of organic being can be fossilized (Darwin, 486-488). I think Darwin needs to be more specific or open up research on how some of these fossils and which organic classes are lost. Though this argument has nothing to do with his arguments for evolution, I did find it unconvincing that natural selection provides good reasoning for artificial selection (Darwin, 489). Although it does cover with an easy ‘yes’ using artificial selection to fix diseases, it doesn’t give a fair look into the some of the ethical concerns involved.