Map of life expectancy at birth from Global Education Project.

Friday, August 04, 2006

It's Hard Work

So where am I going with this? I think that people find evolution hard to accept principally because it only makes sense when you have enough information, enough pieces of the puzzle, to put together the big picture. Our schools aren't giving people enough of those pieces, so the fragments they do hear about just don't make sense to them.

My previous post had a lot of fairly mind boggling information, and it assumes that people already have a lot of background. Some ideas I would venture to say that the large majority of Americans do understand, for example that all life consists of microscopic elements called cells, and that the big things we can see, including us, cosist of vast numbers of cells, while some organisms consist of only a single cell.

But the basic idea of DNA -- that it is a chemical which somehow encodes the instructions for making chemicals essential to life, that in the multicellular organisms, it somehow controls the developmental process that creates the structure of the body and the functioning of its various organs, and that it is sometimes copied imperfectly, making changes in the organism possible over time -- is probably pushing the envelope. (Actually, it's even a bit more complicated than that. Development depends on the interaction between DNA and the cellular environment that unfolds beginning with the zygote, that cell formed from the fusion of the gametes.)

I also invoked events that happened more than a billion years ago. Who can really grasp such a vast extent of time? But appreciating the time scale is essential to the credibility of evolution, because evolution depends on improbable events. Suppose something happens only once in a thousand years. During the lifetime of 95% of humans, it will never occur. But in a million years, it will occur a thousand times, and in a billion years, it will happen a million times.

Finally, I asked people simply to accept the existence of prokaryotic cells. But where did they come from? In fact, they had at least a billion and a half years or so to evolve between the time when the cosmic bombardment of the earth by debris from the formation of the solar system slowed sufficiently for life to exist, and the emergence of the eukaryotes. But how did the whole thing get started? How could life come about from warm, polluted water?*

We don't know, but we do have plausible ideas. As Prospero asked Ariel, "What seest thou else, in the dark backward and abysm of time?" As regular readers know, I don't normally post on Saturdays because I'm busy with a project. But I will return to this thread on Sunday.

*I note that it is only in very recent times, and thanks to science, that people actually started to find this implausible. Just a couple of hundred years ago, it was widely believed that flies developed spontaneously from rotting meat, and that mice appeared de novo in piles of grain.

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