In Darwin’s last chapter “Recapitulation and Conclusion”, he poses several arguments to convince his readers of the role of evolution through natural selection. He talks about how you can observe the variety produced by selective breeding, and that there isn’t any reason that change and variety doesn’t exist in nature as it does with the manmade domestication of species (Darwin, pgs. 488-489). Darwin also argues that the individuals that have a slight advantage over their opponents will be the ones to succeed, and also to produce the most offspring (Darwin, pg. 491). Of course, these variations occur at a slower pace in nature than they do under man’s thumb, but Darwin argues that this process of natural selection is akin to the manmade version, just slower. He also talks about how natural selection acts through competition and that new species have appeared slowly, though this process of natural selection, though the changes observed are different for different groups (Darwin, pgs. 493, 496). Darwin also talks about how depending on the climate, the adaptions will be different for different species (Darwin, pg. 499). These are several of the arguments that Darwin poses for the argument that evolution is due to natural selection.
I think the most convincing of Darwin’s points that I found most convincing was his argument regarding the selective breeding that mankind using to utilize the aspects of a plant or animal that they find the most useful. I thought this was a particularly convincing argument because he’s right, you can see the definite differences from generation to generation of a species when you selectively breed for a certain trait. He then connected this with the traits that emerge in nature over time as the dominant features of a species, through the process of slower natural selection. This was the most convincing to me.
I completely agree with your second paragraph that selective breeding was a hugely convincing point. Many of the other things that he talked about were fairly convincing, but selective breeding gives us very clear evidence of how we have evolved animals in just the past couple thousand years. Animals like dogs are perfectly tangible evidence of this.
I think that yes, human selective breeding does show which characteristics humans see as most valuable in animals, but I may be missing how this fact helps to proves Darwin’s theory of evolution through natural selection. I think the attributes that humans assign as “positive” in animals do not necessarily always correlate to those that will serve an animal to carry out its genes in the wild. I may be missing the point of your first paragraph though. I definitely agree that our ability to breed for certain traits and manipulate genes shows that gene modification through natural selection is very powerful.