The Origin of species
I assigned myself the task of reading the second part of the origin of species, a task I found most interesting and at the same time enlightening. Charles Darwin was a revolutionary for his time, and it comes as no surprise that this work was greatly criticized.
In my readings, Charles Darwin lays out the critical points against his work the origin of species and tries to address them properly. The first question he tackles is “why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms?” (pg 135) and “why is not all nature in confusion instead of the species being, as we see them, well defined?” (pg 135). The second question he tackles is that “is it possible that an animal having for instance, the structure and habit of a bat, could have been formed by the modifications of some animal with wholly different habits?”(pg 136). The third question is “can instinct be acquired and modified by natural selection?”(pg 136). The final question is “how can we account for species, when crossed being sterile and producing sterile offspring, whereas, when varieties are crossed the fertility is unimpaired?”(pg 136). In this summary I will highlight the relevant solutions to these problems from the first to the last in that order.
Darwin states “natural selection acts solely by the preservation of profitable modifications” (pg 136) and the new stock will take the place of the parents. This statement implies that there must have been “innumerable transitional forms” (pg 136) that have existed at one point or another. Why then do we not find fossils of these forms? Well the reason, as stated by Darwin, is that the geological records we have are unreliable and limited. Darwin believes that humans cannot account for a significant amount of fossils on the earth and thus are limited and “that numbers of our fossil species are known and named from single and often broken specimen or from a few specimen collected on one spot”. The fossils that have not been found will decay and disappear eventually. Furthermore, organisms are grouped into a concentrated metropolis where their kind is abundant. The farther you get from the metropolis the rarer the organisms a become, and the greater a different organism b is. The other organism b gets larger until it reaches a concentrated metropolis where its kind is abundant. The area between the 2 metropolis of organism a and organism b is an area for the intermediate species, which are small and contain modifications that favor both sides. However by the principle of natural selections, they will be assimilated eventually by the 2 larger groups, passing their modifications to larger the organisms. Therefore new varieties are very slowly formed because the intermediate species are “liable to accidental extermination” and the modifications are passed gradually.
Observe the case of the “Galeopithecus or flying lemur which was formerly ranked under the family of bats” (pg 141). He argues “although no graduated links of structure occur, fitted for gliding in the air, now connects the Galeopithecus with the other Lemuridae, yet I can see no difficulty in supposing that such links formerly existed and that each had been formed by the same steps as in the case of the less gliding squirrels; and each case had been useful to its possessor.” (pg 141) This argument simply implies that animal will modify gradually as habits change just as the case of the squirrel and the flying lemur that have wholly different habits but ultimately are from the same ancestry.
The next question is if instincts can be acquired and modified by natural selection. He argues that it is more than likely. “What can be plainer than that the webbed feet of ducks and geese are formed for swimming? Yet there are upland geese which rarely or never go near water?” (pg 143). The point of this is to highlight the modifications that can occur in organisms based on their environment. The classic example is the case of the woodpecker. In Europe, woodpeckers are known for “climbing trees and seizing insects in the chinks of the bark….”(pg 143) and “yet in north America there are woodpeckers who feed primarily on fruit, and others with elongated beaks which chase insects on the wings; and on the plains of La Plata, where not a tree grows there is a woodpecker, which in every essential part of its organization, even in its coloring…… yet it is a woodpecker which never climbs a tree”. This implies that modifications are dictated by the environment, and therefore natural instincts can be modified by natural selection.
The final questions is why, for example, if you cross a donkey and a horse you get a sterile offspring but when you cross two varieties of the same organisms the offspring are not sterile. Darwin answers this simply by saying this is as a result of two organisms possessing different reproductive organs and because of that conflict do not possess an active organ for reproduction, whereas organisms of the same species have similar organs and therefore do not suffer any conflicts.
In conclusion, I have to commend this work as Darwin highlights several examples to prove his points. I felt that he was in the habit of repeating most of his points and it made the whole work feel sort of like a déjà vu. But I credit this flaw to the spirit of the time. He had to continually hammer his point in so that the reader could follow his logical path.