To help convince readers of his theory of natural selection, Darwin used a multitude of arguments. He began by addressing the obvious counterpoints, specifically addressing the arguments of a lack of geological record of species that had gone extinct that were “in between” the variations of species we see today. He states that we have not seen enough of the geological record of the world, and therefore the geological record that we have seen is not accurate or definitive. He then addresses the counter argument that states that natural selection would not result in similar species around the globe. Darwin points to large migrations as the cause for widespread similar species. He then continues on to give characteristics of animal life on Earth that are readily explained by the theory of natural selection. This includes comparisons of the breeding for specific traits in domestic animals by humans to the ability of nature to “breed” for characteristics of the course of millions of years. He also argues that the variability in animals, specifically birds, is much better explained by evolution than creationism. Why, for example, do upland geese have webbed feet, despite rarely going for a swim? Darwin says that the similar bone structures of horses and giraffes, man’s hands and bat wings, are all explained by a theory of descent with slow modification. Finally, Darwin wraps up by explaining the scope of his work.
In my opinion, Darwin’s most convincing argument for his theory of natural selection is his comparison of the similar bone structures and features in animals that have no shared needs. If humans cannot fly, and bats do not pick up tools, why do we have similar skeletal arrangements in our appendages? Darwin’s least convincing argument is the inaccuracy of the geological record. I understand the argument, but it feels slightly lazy or “too easy” to simply state that the geological record isn’t completely right.