The following design argument is atypical. It is not based on the principal of irreducible complexity, nor does it require evolution to produce a specific organ/organelle. It calculates the probability of evolution producing a certain level of biological complexity and compares this probability with the number of trials available for evolution to that level. Please approach it with a completely open mind.
An E. coli bacterium has around 4,000 protein-coding genes, a mouse has around 24,000, a chicken has around 19,000, zebrafish 22,000, and man 24,000 (Brown, 2007). These numbers are likely to be refined with further research; for example, the latest estimate for man is >18,000 protein-coding genes (Segal et al, 2008). Nevertheless, it is clear that any one of the thousands of extant vertebrate species possesses at least 10,000 more protein-coding genes than a bacterium. The primordial single-celled organism from which all these vertebrate species evolved was roughly similar to a modern bacterium. Thus, at least 10,000 protein-coding genes must have been added during the course of evolution from a primordial single-celled organism to produce any of the thousands of extant vertebrate species.
During the course of evolution, a new gene arose by processes such as the duplication of an existing gene followed by exon shuffling, point mutations and other mutations. After a new gene appeared in an individual, the rate at which this gene spread throughout the population depended on how beneficial it was to this individual, as well as how beneficial other genes in that individual were relative to the rest of the population. Even a very beneficial gene spread very slowly or not at all if it was in an individual whose overall genetic makeup was much less fit than the average. Conversely, an inferior gene can become prominent in the population if it is in an individual whose overall genetic makeup is far superior to the norm. The phenomenon in which an inferior gene rises to prominence by virtue of its association with other genes that happen to confer a fitness advantage is called “hitchhiking” in the discipline known as population genetics. The probability that a new gene was produced by mutations and subsequently spread throughout a population was obviously less than the simple probability of its production by mutations.
What is this probability? Many studies have explored the effects of deleting various combinations of the genes responsible for DNA proof-reading and repair. These studies found that the maximum mutation rate per generation per gene for extant bacteria is 10-3 (Marcobal et al, 2008). This is the rate in bacteria undergoing extreme hardship, such as starvation; when released from such duress they return to their normal mutation rate of 10-6 per generation per gene. Mutation rates for vertebrates (whether normal or under duress) are never greater than those for bacteria. Let us assume that one mutation of probability 10-3 was sufficient to produce a new gene useful for vertebrate evolution.
So, the probability that evolution produced any vertebrate species is 10-3 multiplied by itself 10,000 times, which equals 10-30,000.
Would this probability be significantly greater if, during the course of evolution, extensive lateral gene transfer between dissimilar organisms had occurred? Although gene transfer was involved in prokaryotic and single-celled eukaryotic evolution, it does not appear to have played a significant role in the evolution of vertebrates (Andersson, 2005; Kurland et al, 2003; Salzberg et al, 2001; Kurland, 2000). Even if it had played a significant role, it is not clear it would have increased the probability of vertebrate evolution, since the donated genes must have undergone an evolutionary process in the donor organism, and the probability is very small that the donor organism just happened to encounter, and then successfully transfer, the needed genes into a suitable receiving organism. Genetic exchange between dissimilar vertebrates is not as simple as it is between bacteria, which have a special organelle for this, namely the pilus. Moreover, organisms do not maintain for long periods of time functional versions of genes that are not useful for them. Thus, it appears that suitable donors and receivers need to meet at the right time, which requires events of very low probability.
The probability of vertebrate evolution starting from the Big Bang is much less than 10-30,000 since we must multiply 10-30,000 by two factors: (A) the probability that the Big Bang’s initial parameters were such that they produce a star with a planet with a primordial soup, and (B) the probability of the appearance of a bacterium in this soup. Both of these factors are believed to be very small; by some estimates, they are as small as 10-30,000. We did not attempt to calculate them since, at present, there is insufficient information.
What is the significance of this probability? Imagine you are flipping coins with two of your friends and you desire a particular result, namely all heads up. The probability that your coin will be heads up on any flip is ½, which is also the probability of heads up for each of your two friends. Thus, a trial in this case consists of three coins being flipped by three people. The probability that all three coins will be heads up on any trial is ½ times ½ times ½, which is 1/8. If you and your friends perform dozens of trials, you will notice that, on the average, out of every eight trials, one trial has all heads up. Eight is the reciprocal of 1/8. If four people are flipping, you will find that, on the average, out of every 16 trials, one trial has all four heads up. If ten people are flipping, you will find that out of every 1000 trials, one trial has all 10 heads up. If 1000 people are flipping, you will find that, out of every 10300 trials, one trial has all 1000 coins with heads up. Thus, we arrive at the very important rule that, if the number of trials is of the same order of magnitude as the reciprocal of the probability of a particular result, that result is expected to occur on one of the trials simply by chance, without design being involved. This is standard statistics (see any textbook on statistics). So, design can be inferred when the number of trials is many orders of magnitude smaller than the reciprocal of the probability. For example, if you and a thousand friends are flipping coins and all of you get heads up within the first ten trials, you would suspect design.
Thus, to avoid the conclusion that vertebrates were designed, of the order of 1030,000 evolution-supporting planets must now exist or have existed in the past, which requires: (A) a single large universe with that many planets, each of which exhibits some stage of evolution from the primordial soup up to vertebrates, or (B) nearly that many small universes, each of which has a few such planets, or (C) a small universe with a few such planets that had undergone nearly that many Big Crunches and subsequent Big Bangs. Regarding (A), only a few hundred extra-solar planets have been detected so far. Since it becomes more difficult to detect a planet the further from the earth it is, we can safely conclude that there is no way that even an insignificant fraction of 1030,000 evolution-supporting planets will be detected within the next few decades. The speed at which light reaches us and the speed at which electrons move through semiconductors in our computers impose fundamental limits on the speed at which even the best equipment can operate. Suppose this equipment can identify a new planet every pico-second (10-12 seconds), which is an outrageous rate far beyond present or conceivable technology. This still means that we must wait 1029,980 years to identify the number of planets needed for the chance hypothesis. Regarding (B), the unambiguous detection of a few other universes is presently considered difficult work, if it can be done at all, not to mention observing life on planets within those universes (Aguirre et al, 2007). Even if we had equipment capable of identifying a suitable planet in another universe every pico-second, we would still have to wait 1029,980 years to verify the existence of the number of evolution-supporting planets required for the chance hypothesis. Regarding (C), even if each pico-second we could verify that our universe had, in the past, undergone a cycle of Big Crunch and subsequent Big Bang, we would still have to wait 1029,980 years to verify the existence of the number of cycles required for the chance hypothesis. This means that the chance hypothesis is effectively unverifiable. Unverifiable hypotheses are scorned in science and quickly discarded when a verifiable hypothesis arrives. Hence, if there is a verifiable way to contact the designer, then the design hypothesis is superior to the chance hypothesis.