Let's get the next discussion started. I was a little behind due to my Finals week starting, but I managed to get some reading in. I don't know exactly where to start this weeks discussion. I don't know that I am grasping the book as well as I should be so I plan to read through this chapter again. I had several concepts I needed to look up or research and I want to go back through and get a better understanding of Dawkins' concepts. Anyone can feel free to ask questions/comment on anything they found an interest in!
Thanks again for reading along!
For me, the reason I wanted to revisit this book (and I am thoroughly enjoying doing so) is that I don't really recall a lot of the details from the 1st time (which was about a year ago. i listened to it on audiobook in my car, about an hour or so each day.) I did, however, know that I wanted to come back to it someday and give it the attention it deserves. Intellectually, I've taken for granted that evolution is a fact since some time in my early 20's (which would be 20 years ago), but, I sadly admit, that I never really took the time to learn very much about the details. So over the years there have been the uncomfortable encounters here and there, with persons opposed to evolution, wherein they put forth some of the standard objections--i.e. "if humans evolved from apes, why are there still apes?" and everyone's favorite, "well, it's JUST a theory", etc--and I didn't know how to respond, and it was embarrassing and I felt the fool. I mean I didn't think I was wrong, i just felt dumb for not being able to answer some very simple things about evolution and how it works. Which brings me back to The Greatest Show on Earth. I really wanted to go through this book again more carefully because when the occasion does arise where I have to defend evolution or just answer questions about it from someone who is actually interested, I want to be ready this time.
So, as I see it, the three basic points made by Dawkins in chapter one are:
a) there is a large contingent of theologians who readily support the claim that evolution is a fact,
b) that to say that evolution is "just a theory" is to, willfully or otherwise, misunderstand the difference
between a scientific theory and an hypothesis, and,
c) to say that evolution has "never been proved" is to, willfully or otherwise, misunderstand the scientific method and the difference between "actual observation and authentic testimony" and scientific inference.
Ok, so chapter 2. While I think that Dawkins' discussion of Platonic essentialism as a cause for the delayed "discovery" of evolution is interesting, I don't really buy it as being the whole story. And I don't really understand why Dawkins would be so reductionist about it. Although, to be fair, he really is just relating Ernst Mayr's theory, and it does work well as an intro to the next section of the "hairpin thought experiment." Since ultimately this book is about the evidence for evolution I can see why Dawkins wouldn't want to spend more time and space discussing the ideas (or lack thereof) and beliefs that acted as barriers to the idea of evolution. In the very 1st paragraph he does say however, "Perhaps minds were cowed by the sheer time it must take for great change to occur...Perhaps it was religious doctrination...perhaps it was the daunting complexity of...an eye, freighted as it is with the beguiling illusion of design by a master engineer." Obviously, it was all these things, as well as platonic essentialism and all kinds of other things, including the basic arrogance of human beings which prevented (and still prevents) them from seeing themselves as a direct part of the natural world, and ultimately mere animals (albeit very smart animals.)
I know for sure from other reading that one of the major obstacles was the estimated age of the earth.
Obviously, evolution requires a great deal of time and the problem was that, at the time, the age of the earth was far from being the ~4.5 billion years old that we think of today. I mean, according to those who used the bible as the authoritative source, the earth had only been created something like 6 or 7 thousand years ago (October 23, 4004 B.c. according to Bishop Ussher!). As I recall, scientists at the time were thinking something more along the lines of 20 to 50 million years old or so. Which is still far short of our current understanding, which (according to Age of the Earth ) didn't come around until the 1950's. So, in fact, I think that one of the things that has actually made Darwin's agrument more obvious is the expanding understanding of the age of the earth.
This is the beginning of the evidence, or say rather, the beginning of the presentation of the whole case. In chapter 2 Dawkins is first of all giving us a nice model to have in your head when thinking about the divergence of species. That is what the “hairpin thought experiment” is all about. I actually liked this part of the chapter a great deal. What I'm looking for, as I said above, is to clarify my thinking about evolution and how it works. When I was reading this section I realized that the way I had been thinking about species is one thing that still had me confused. I was thinking of species as sort of like a closed group, closed in both space and time. So I knew that evolution primarily occurs as gradual change over time, but I still had a block when it came to imagining one species changing into another. Like I would picture at some point in the distant past there being a certain species (species 1) of something-or-the-other (that is now extinct), and then I would picture a species (species 2) that was descended from that earlier species, but still see a sort of gap in between the 2 species, a gap into which I really didn't know what belonged. Like what was it exactly that had happened in between species 1 becoming species 2.
But as I was reading this “hairpin thought experiment” section, I had one those “ah ha!” moments. The fault in the way I was thinking about it was the “gap.” There is no gap, ever. Because there is always an unbroken chain of descendants from one group to a later group. It made me think of how when people trace their ancestry they always go back to a certain point (usually, I guess as far as you can based on records) which usually ends with a certain person (somehow usually someone famous), or a general area, i.e. “our family originally came from Hungary.” And that's it. But that's not it. They could trace, by direct lineage an ancestry to Hungary, but they could keep going, one by one, as Dawkins does following daughter to mother and on all the way back until after about 4 million or so years they'd find that their ancestors looked a lot like hairy little bipedal monkeys (Lucy). And if they kept going, from individual to individual, daughter to mother, for another 2 or so million years worth of ancestors, they would find themselves standing next to the last common ancestor of humans and chimpanzees (Wikipedia link: Chimpanzee-human last common ancestor.)
Now here's a point that I think Dawkins didn't quite make clear. When they have reached this point and are ready to make that “hairpin” turn, and start following the species forward again, walking along a chain of descendants back to the future and eventually arrive at Chimpanzees; they can't start from the same individual from which they had previously traced their individual ancestry to. This is where the next part of the chapter comes in, the gene pool discussion. The person walking their ancestry, now standing among a group of small, primatish, tree-dwelling mammals, would have to find another individual from that species' gene pool [or, I guess it's possible that you could start your walk back starting from that same individual, but you'd have to follow a different daughter]. So anyway, the thing is, it is from somewhere in the gene pool of this common ancestor, from some specific individual, that you could walk back, following from mother to daughter, all the way, one individual at a time, to modern day Chimpanzees. That's just awesome to me!
"When you talk about following back to the 4 to 6 million years ago range and not being able to follow back from that same person to a different species, it makes me wonder, why not?"
What I was thinking is that if you had followed the individuals back in time, one by one, daughter to mother, until you had arrived at a specific ancestor 6 million years ago, that you couldn't then just turn around and follow back from that particular individual because it would lead you right back where you came from. As you said, "In my mind I see that as we travel back 6 million years there is only one path we can take." That is exactly the same way I see it, and I think, exactly how Dawkins means it.
I guess my initial thought was something like this: now, having arrived 6 million years ago, and you're standing next to that individual that your path has taken you to; when you turn around, to make that hairpin turn, if you followed the daughter of that same individual then it would just lead you back. I guess that's why I threw in that "follow a different daughter" comment. I guess I hadn't formed a clear idea about the walk back, only knowing that from the point that you have arrived it would be possible to follow an unbroken chain of direct descendants from the common ancestor (that you had reached by walking back in time from a human) back to present day Chimpanzees.
I think you put it better when you say, "when we turn around there is an infinite amount of choices we can make to arrive at all the different species and ancestors of the chain." The walk back is definitely more complex! There are a lot more choices to make because of all the branching off.
Hello fellow readers,
Sorry for the delay in my responses, I have successfully finished my finals, and my reading for the week. I do apologize, I thought I would have enough time to complete both but a few twists and turns prolonged this response.
This chapter is a good start for me, I do not understand much more than the general concept of Evolution, and this has explained to me where some of the general ideas have been gathered. I concluded from this chapter that the genetic changes that we can 'force' upon other life (Dogs, Cattle, Cabbages, etc.) are very similar to those that can, and will, occur naturally over time. The part I wanted to hear more on is why these changes take so long to occur naturally, but I'm sure that will be addressed shortly. As i see it the changes that are made naturally are for a cause of some sort, and usually they are started due to a need of the life forms that is required for survival. Am I getting that part of it correct?
I don't think I have much else to post about this chapter. I will be looking forward to the chapter three reading and posting the new discussion Sunday or Monday. Thanks again for joining me.
Always nice to have finals behind you :)
Yeah, I agree, it seems that the rest of the chapter (that I hadn't commented on: gene pools, dogs, cabbages, artificial selection) is to demonstrate some basic ideas that are going to be very important in understanding the actual process of evolution by natural selection. I was especially bowled over by the discussion of the cabbage! I had no idea that "broccoli, cauliflower, kohlrabi, kale, Brussels sprouts, spring greens, romanescu..." were ALL derived from cabbage. Wow.
That was a new one for me too. The more obvious one is the Cauliflower and broccoli relation, but i had no idea the rest were connected. I think that's one of the area's that i am most interested in, seeing what other connections there are that have a closer relation than 6 million years ago. i know this sort of thing takes time, but an example that had me just amazed is Stone Fruit. The idea that they can plant one tree and graft (sp???) other branches into it, causing one tree that originally produced plums to also produce apricots, nectarines, and peaches. There are so many things like this that appear to be the forced adaptation that he has talked about in the chapter that I am so intrigued by.