The origin of life and the first cell
A modern cell, even of a simple organism like a bacterium, is intensely complicated. The cell membrane is studded with receptors like keyholes that allow sophisticated communication among cells. The cytoplasm, the fluid making up the interior of the cell, hosts elaborate biochemical pathways that process and propagate biological signals. Complex structures called ribosomes are like sliding clamps with integrated information readers; they produce new proteins in assembly-line fashion.
Proponents of the pseudo-scientific theory "Intelligent Design" (ID) use the above examples as evidence to suggest that no natural process could have resulted in a cell. In ID, cells are purported to be "irreducibly complex," meaning they cannot function in the simpler forms that would be expected according to the theory of evolution.
One cannot prove a negative; a single example to the contrary falsifies a negative statement. Inconveniently for ID proponents, recent research is working steadily to falsify this particular negative statement.
While modern cells possess the array of machinery described above and more, no researcher has ever shown that all of it is absolutely necessary for life to exist. According to one astrobiologist, Peter Ward, the bare minimum for a cell to live, metabolize, and reproduce may be no more than a membrane to separate cell contents from its surroundings and a bit of genetic material.* And Scientific American recently reported that Harvard Medical School researchers have caused this type of structure to arise spontaneously in a test tube. They mixed certain organic molecules (ones thought to have been around in earth's early pre-life days) in a test tube of water.
The result seems like wildly optimistic science fiction: some of the molecules (lipids, which are the building blocks of oil and fat and which don't mix with water) spontaneously formed a "pouch" with another molecule (DNA) inside, then more molecules (nucleic acids, building blocks of DNA) spontaneously crossed the barrier, and the DNA spontaneously replicated.
Did I mention that all this took place spontaneously, with no tinkering from an intelligence? Not only that, it required no more than 24 hours. Chalk up a blow to the argument that the cell is irreducibly complex.
| *Actually, Ward suggests the minimum definition of life may be considerably less even than that. I am currently reading, and must recommend, his book Life As We Do Not Know It: The NASA Search for (and Synthesis of) Alien Life. | |
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greylorn · 855 weeks ago
The concept of "irreducible complexity" was introduced by Michael Behe in "Darwin's Black Box," essential reading for anyone either within or without the Intelligent Design movement who tries to apply the concept to cells. Behe applied the concept to mousetraps, then to some of the molecular machines found within cells--- not to the cell itself.
Finally, I believe that knowing what DNA and lipids are, then gathering up samples uncontaminated by other organic compounds, and putting them in a test tube requires intelligence. For that matter, so does blowing a suitable test tube.
Kindly accept these comments in the spirit of debate. This subject is important, but fair debate can only be built on a foundation of valid information. Thank you.
Ginkgo100 38p · 855 weeks ago
On p. 121 of the book by Ward that I mentioned in this post, he writes "Only in the late twentieth century and the first years of the twenty-first has progress on this front [demonstration of natural synthesis of nucleotides] continued in anything like a promising fashion. But progress there now is...." Unfortunately, he does not cite any studies; on the other hand, the current abscence of evidence is certainly not evidence of abscence; in other words, there is nothing to suggest that nucleotides cannot be produced through natural processes.
You make a good point that what was produced in this experiment was the product of intelligent design -- the design of the researchers. Still, I think the lack of "tinkering" that was necessary to get these results is striking.