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Tuesday, November 30, 2010

"Geo" Things - Everything We Don't Know (Chapters 9, 10, 11, and 12)

Hello, again! Just thought I'd note that we're over halfway through the book! Time flies when you're summarizing!

The next few chapters are about GEOlogical records and GEOgraphical distribution. It's also about all the things we are ignorant of - such as all the fossils we have missing and all of the details of the past (migration, ice ages, etc) that we fail to consider.

Darwin spends two whole chapters discussing fossils. In chapter 9 "On the Imperfection of the Geological Record," he asserts in many more words than necessary that even though we do not see intermediate species in fossils, the theory of Natural Selection still stands. We just have a really lame fossil record. I find this point well emphasized, since it is included in the name of the chapter, a name of a section of the chapter (On the poorness of our Paleontological collections), and throughout the chapter itself. I'm convinced!

Chapter 10 beings,

"Let us now see whether the several facts and rules relating to the geological succession of organic beings, better accord with the common view of the immutability of species, or with that of their slow and gradual modification, through descent and natural selection" (312).

In other words - Let's see if fossils prove my point or special creation?

Since this is Darwin's book, I think it would be safe to assume that the following chapter will prove his point.

One of the most interesting points, that is somewhat obvious but that I never stopped to think about is that once a species is gone it never comes back. "When a species has once disappeared from the face of the earth, we have reason to believe that the same identical form never reappears" (313). I've always known that once an species is extinct it is gone forever. But I think of it differently when considering Natural Selection. Closely related species still exist, so now I would think that variations could "bring" back the same species. But extinction is just as final as it always was.

To further support his theory, Darwin mentions that extinct species are always less related to extant (living) species the longer ago they went extinct. He then suggests, "Let us see how far these several facts and inferences accord with the theory of descent with modification" (331). Oh, Darwin. You just love setting yourself up for a win, don't you? According to descent with modification, each generation consists of small changes that accumulate to make big changes. The longer the time, the more the change. So, yes, this fact does support Darwin's theory. Surprise!

Just an interesting fact, which you should not remember on your next Biology exam, because part of it was discredited:

Darwin mentions that, according to Agassiz, "ancient animals resemble to a certain extent the embryos of recent animals of the same classes" (338). In other words, embryos look more similar to their ancestors than the full grown animal does. The reason I like this theory is because of one of the names for it (this is the discredited part): Ontogeny recapitulates phylogeny. Say that three times fast. Or just use it in any argument and your opponent will assume you know what you're talking about. It means that the developments from zygote to birth replicate the evolution of the species. This is not true. But it is interesting!

Now, chapter 11 "Geographical Distribution" and chapter 12 "Geographical Distribution - continued"

Essentially, Darwin says that all member of a species originated from one ancestor. But to prove this, he must explain how members of the same species ended up in different places...otherwise they would each have been created in the new geographical spot, which would kind of mess up Darwin's theory. Darwin's answer is basically that the make up of the earth wasn't always the way it is now...some places were more reachable than they seem (islands were closer together, etc) and that the one species did, in fact, migrate from one place. The opposite is also true - the places that are truly harder to reach have less common species with places around the world, because species could not migrate to them. He also shows, through many experiments, that plants can do the same by being transported via water (water itself, and fish) and air (birds).

Here is a true eccentricity of Darwin. Not even a mini one. A real one. But it happens to not be explained in the book, so just take my word for it. Darwin and his son would do experiments on dead birds...putting seeds inside them and having the dead bird float inside a bowl or their tub for a certain length of time to see if a seed would survive in the water in a dead bird. That's not my idea of a fun experiment, but, you know, to each his own.

Darwin's last sentence of Chapter 11 is the following:

"The various beings thus left stranded may be compared with savage races of man, driven up and surviving in the mountain-fastnesses of almost every land, which serve as a record, full of interest to us, of the former inhabitants of the surrounding lowlands" (382).

What I want to point out here, is one of the few mentions of the human race. Here, Darwin equates "savage" men, or uncivilized ones, I would assume, to animals that migrate in order to survive and then remain separate from other species. Now, I'm a firm opposer of Social Darwinism, and I don't believe that Darwin intended his theory to be used as justification for subjugating other humans. However, he does mention the "savage man" a couple of times, and I always make note of it, just because it makes a clear statement about how people of his time thought. Darwin clearly was a man who thought out of the box, and yet he still compares "savage" humans to other species, as if they were not even human at all.

Chapter 11 and Chapter 12 are definitely connected, and I've somewhat blended my summary of the two together. Just FYI, chapter 12 is more focused on islands, which makes it special and different from chapter 11!!

I'm a fan of the gardener metaphor in chapter 12:

"Nature, like a careful gardener, thus takes her seeds from a bed of a particular nature, and drops them in another equally well fitted for them" (388).

In other words, plants and animals can survive in more than one area. Short, but sweet, right? It's just a pretty sentence.

Another one liner is a sarcastic one that Darwin asks when discussing how bats seem to be one of the only mammals that occur on islands:

"Why, it may be asked, has the supposed creative force produced bats and no other mammals on remote islands?" (394).

The answer is: It (the creative force) hasn't. (Detailed answer: bats are one of the only mammals that can transport itself across the ocean, and therefore migrate to the islands. They were not created there specially.)

And just in case none of this made sense to you, as per usual, Darwin summarizes both chapter 11 and 12 at the end of this chapter. (But don't tell anyone that I told you.)

Until next time!

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