In the laboratory -we can take molecules of water, ammonia, and methane-rather like the ones we've been talking about for Titan-and dissociate them by ultraviolet light. The fragments make a set of precursor molecules, including hydrogen cyanide, which then combine and, in water, form the amino acids. In such experiments not just the building blocks of the proteins but the building blocks of the nucleic acids are routinely produced. There is a range of subsequent experiments, in which the smaller molecular building blocks join together to form large and complex molecules.
If we look at the fossil record, we find that there is a range of evidence for microfossils dating back not just to the beginning of the Cambrian but dating back to as much as 3,500 million years ago.
Now, just think about these numbers. The Earth itself forms about 4,600 million years ago. Because of the final stages of accretion, we know that the Earth environment was not suitable for the origin of life back then. From studies of the late crater-ing on the Moon, it looks-since the Earth and the Moon were presumably in the same part of the solar system then as now- as if the Earth was not in a suitable state for the origin of life until perhaps 4,000 million years ago. So if the Earth is not appropriate to the origin of life until 4,000 million years ago and the first fossils are around 3,500 million years ago, then there are only about 500 million years for the origin of life. But those earliest fossils are by no means extremely simple organisms. They are, in fact, colonial algal stromatolites, and a great deal of evolution had to precede them. And that therefore says that the origin of life happened in significantly less than 500 million years. We don't know how much less. Six days was once a popular hypothesis. It's not excluded by these data, but at least it cannot be as long as 500 million years. It must have happened very fast. A process that happens quickly is a process that in some sense is likely. The faster it happens, the more likely it is. There is a difficulty in extrapolating from a single case; nevertheless this evidence suggests that the origin of life was in some sense easy, in some sense sitting in the laws of physics and chemistry. And if that's true, that is a very important fact for the consideration of extraterrestrial life.
There is a classic objection to this kind of argument about the origin of life. As far as I know, this objection was first posed by Pierre Lecompte du Noiiy in a 1947 book called Human Destiny and is regularly rediscovered about once every half decade. It goes something like this: Consider some biological molecules. Not all of them. We'll give the evolutionists the benefit of the doubt. Let's just take a small, simple one, not something thousands of amino acids long. Let's pick an enzyme with a hundred amino acids. That's a very modest enzyme. Now, a way to think of it is as a kind of necklace on which there are a hundred beads. There are twenty different kinds of beads, any one of which could be in any one of these positions. To reproduce the molecule precisely, you have to put all the right beads-all the right amino acids-in the molecule in the right order. If you were blindfolded while assembling a necklace from equally abundant beads, the chance of getting the right bead in the first slot is 1 chance in 20. The chance of getting the right bead in the second slot is also 1 chance in 20, so the chance of getting the right bead in the first and second slots simultaneously is 1 chance in 202. Getting the first three correct is 1 chance in 203, and getting all hundred correct is 1 chance in 20100. Well, you can see 20100 is 2100 x 10100. And since 210 is a thousand, which is 103, then 2100 is 1030, so this is the same as 10130. One chance in 10130 of assembling the right molecules the first time. Ten to the hundred-thirtieth power, or 1 followed by 130 zeros, is vastly more than the total number of elementary particles in the entire universe, which is only about ten to the eightieth (1080).
So let's imagine that every star in the universe has a planetary system like ours. Let's say one planet has oceans. Let's suppose that the oceans are just as thick as ours. Let us suppose that there is a few-percent solution of organic matter in every one of those oceans and that in every tiny volume of the ocean that has enough molecules there is an experiment happening once every microsecond to construct this particular hundred-amino-acid-long protein. So in the ocean every microsecond an enormous number of these little experiments are going on. And identical things are happening in the next star system and the next star system, filling an entire galaxy. And then not just in that galaxy but in every galaxy in the universe. It turns out that if that sequence of experiments had gone on for the entire history of the universe, you could never produce one enzyme molecule of predetermined structure. And in fact it's much worse than that.
If you did that same experiment once every Planck time, the shortest unit of time that is permissible in physics, you still couldn't generate a single hemoglobin molecule, from which many people have decided that God exists, because how else do you make these molecules? If you haven't heard this before, doesn't this seem like a pretty compelling argument? Strong argument, right? A whole universe of experiments once every Planck time. Can't beat that.
Now let's take another look. Does it matter if I have a hemoglobin molecule here and I pull out this aspartic acid and I put in a glutamic? Does that make the molecule function less well? In most cases it doesn't. In most cases an enzyme has a so-called active site, which is generally about five amino acids long. And it's the active site that does the stuff. And the rest of the molecule is involved in folding and turning the molecule on or turning it off. And it's not a hundred places you have to explain, it's only five to get going. And 205 is an absurdly small number, only about 3 million. Those experiments are done in one ocean between now and next Tuesday. Now, remember what it is we're trying to do: We're not trying to make a human being from scratch, to have all the molecules of a human being fall simultaneously together in a primitive ocean and then have someone swim out of the water. That's not what we're asking for. What we're asking for is something that gets life going, so this enormously powerful sieve of Darwinian natural selection can start pulling out the natural experiments that work and encouraging them, and neglecting the cases that don't work.
So it turns out here, as in some of the arguments I was talking about yesterday, there is an important point that is left out in these apparent deductions of divine intervention by looking at the natural world. A very dramatic, strong statement of this sort has been made by the astronomers Fred Hoyle and N. C. Wick-ramasinghe. And their phrase, after a calculation in this spirit, goes something like this:
They say it is no more likely that the origin of life could occur spontaneously by molecular interaction in the primitive ocean than that a Boeing 747 would be spontaneously assembled when a whirlwind passed over a junkyard. That's a vivid image. It's also a very useful image, because, of course, the Boeing 747 did not spring full-blown into the world of aviation; it is the end product of a long evolutionary sequence, which, as you know, goes back to the DC-3 and so on until you get to the Wright biplane. Now, the Wright biplane does look as if it were spontaneously assembled by a whirlwind in a junkyard. And while I don't mean to criticize the brilliant achievement of the Wright brothers, as long as you remember that there is this evolutionary history, it's a lot easier to understand the origin of the first example.