Thursday, January 12, 2006

The evolution debate...

I did say that I thought this was going to be an interesting site to puddle in. And sure enough that it is how it seems.

Take this as an example. If, as I hope you will, you read the full transcript you will find that it is dated 1997.

In view of the present and persistent debate of evolution vs whatever kind of divine intervention suits your fancy I want to quote just the last two pages...

You contain a trillion copies of a large, textual document written in a highly accurate, digital code, each copy as voluminous as a substantial book. I'm talking, of course, of the DNA in your cells. Textbooks describe DNA as a blueprint for a body. It's better seen as a recipe for making a body, because it is irreversible. But today I want to present it as something different again, and even more intriguing. The DNA in you is a coded description of ancient worlds in which your ancestors lived. DNA is the wisdom out of the old days, and I mean very old days indeed.

The oldest human documents go back a few thousand years, originally written in pictures. Alphabets seem to have been invented about 35 centuries ago in the Middle East, and they've changed and spawned numerous varieties of alphabet since then. The DNA alphabet arose at least 35 million centuries ago. Since that time, it hasn't changed one jot. Not just the alphabet, the dictionary of 64 basic words and their meanings is the same in modern bacteria and in us. Yet the common ancestor from whom we both inherited this precise and accurate dictionary lived at least 35 million centuries ago.

What changes is the long programs that natural selection has written using those 64 basic words. The messages that have come down to us are the ones that have survived millions, in some cases hundreds of millions, of generations. For every successful message that has reached the present, countless failures have fallen away like the chippings on a sculptor's floor. That's what Darwinian natural selection means. We are the descendants of a tiny Žlite of successful ancestors. Our DNA has proved itself successful, because it is here. Geological time has carved and sculpted our DNA to survive down to the present.

There are perhaps 30 million distinct species in the world today. So, there are 30 million distinct ways of making a living, ways of working to pass DNA on to the future. Some do it in the sea, some on land. Some up trees, some underground. Some are plants, using solar panels - we call them leaves - to trap energy. Some eat the plants. Some eat the herbivores. Some are big carnivores that eat the small ones. Some live as parasites inside other bodies. Some live in hot springs. One species of small worms is said to live entirely inside German beer mats. All these different ways of making a living are just different tactics for passing on DNA. The differences are in the details.

The DNA of a camel was once in the sea, but it hasn't been there for a good 300 million years. It has spent most of recent geological history in deserts, programming bodies to withstand dust and conserve water. Like sandbluffs carved into fantastic shapes by the desert winds, camel DNA has been sculpted by survival in ancient deserts to yield modern camels.

At every stage of its geological apprenticeship, the DNA of a species has been honed and whittled, carved and rejigged by selection in a succession of environments. If only we could read the language, the DNA of tuna and starfish would have 'sea' written into the text. The DNA of moles and earthworms would spell 'underground'. Of course all the DNA would spell many other things as well. Shark and cheetah DNA would spell 'hunt', as well as separate messages about sea and land.

We can't read these messages yet. Maybe we never shall, for their language is indirect, as befits a recipe rather than a reversible blueprint. But it's still true that our DNA is a coded description of the worlds in which our ancestors survived. We are walking archives of the African Pliocene, even of Devonian seas, walking repositories of wisdom out of the old days. You could spend a lifetime reading such messages and die unsated by the wonder of it.

Don't worry, I put my hand straight up and confess confirmation bias. I also put my hand up for quoting without context.

Don't worry, I know that the writer is a scientist.

I also know that (in my mind) his science is pragmatic and forthright.

The reason for the quotation tho' is to try and encourage you the reader to digest the other 13 odd pages, hopefully with an open mind and with the intent of gaining an insight into just how Richard Dawkins sees the true nature of science.

In my opinion, it is good writing and a well-founded analysis.


Dave Justus said...

"The DNA alphabet arose at least 35 million centuries ago. Since that time, it hasn't changed one jot. Not just the alphabet, the dictionary of 64 basic words and their meanings is the same in modern bacteria and in us. Yet the common ancestor from whom we both inherited this precise and accurate dictionary lived at least 35 million centuries ago."

Interestingly enough, this is the very same arguement that ID proponents use as evidence for 'design.' We don't have a good 'scientific' account for how those original 'words' could evolve or come into existence. Random chance is always a possibility of course, but not a very satisfying one considering it would statiticy be beyond the threshold of what is usually considered 'impossible.'

That is one reason many scientists think panspermia, life originating from an extra-terrestrial source (not 'aliens' but bacteria on meteorites or something similar) makes a lot of sense.

I don't think we have any really solid answers for the question of how life first got started. My expectation is that there are natural principles we don't yet understand.

The probligo said...

Hmm, "panspermia". Not a word one would use in casual conversation. Never met it in me life before to be honest, but it makes an element of sense.

To add to that "sense" is a series of reports I have seen over the years recording the likelihood of just such occurences - triggering such events as the 1918 flu, the current "bird flu", the black death, immuno-deficiency viruses, and other periodic medical nasties.

How much credence to place on a possible "statistical correlation" in support of panspermia?. Perhaps a little more than the likelihood of divine intervention.

As I can make no intellectual concept of the time periods involved - like 35x10^8 years, a number rivalling the cost of the Iraq war which I believe to be $2x10^9 - without trying to add on how long the "dictionary" might have taken to evolve prior to that start point. Am I right in saying that the earth / solar system is something like 10^12 years old? I can't remember how long back it was that I thought of the idea... :D

Hey!! Now there is a point. Excluding interest, and saving at 60 cents per year, it would take roughly as long as life has existed on earth to pay for the Iraq war. Boggling.