A basic concept in evolution is that mutations of DNA code, under pressure from natural selection, over long expanses of time, have generated increasing complexity and progression of life forms from simple to complex. Evolutionists admit that most mutations are neutral or detrimental, and not few are lethal. But they shun away from giving specific numbers in terms of the the relative rate of beneficial vs. neutral or detrimental mutations. And for good reason.
Could the eye have evolved through random mutations?
I will briefly discuss here an "example" of how eye evolution could have taken place. This was recently presented to me as strong evidence for evolution.
Two Swedish scientists published about 20 years ago an article cleverly titled "A Pessimistic Estimate Of The Time Required For An Eye To Evolve". What they did was to break down the differences between the modern, complex mammalian eye and the most "primitive" eye possible into many stages that were no more than 1% different from each other, and then, using a model of evolution that favors increasingly more complex eye development, determine how long it would take for the present eye design to evolve. Surprisingly, they state, it would take less than 400,000 years for the eye to evolve. This theoretical model of evolution is often quoted and even embellished (some claiming it was run on computerized models of evolution, which is not true).
The major criticism I have for the model presented in this article has to do with the rates of mutation, the way these mutations would have to occur, and whether random mutations could actually add new information to a genome.
The rates of beneficial mutations observed in real life are a surprisingly dark area in evolution science, which in itself is strange, given that such mutations are supposed to power the very engines of evolution. Except for some specific numbers given for single-cell organisms (bacteria), nobody seems to be able or willing to give specific ratios of beneficial mutations in relation to harmful or neutral mutations in more complex orgasnisms. Just a couple of months ago, this article published in the journal Evolution admitted this much:
Estimates of mutational parameters, such as the average fitness effect of a new mutation and the rate at which new genetic variation for fitness is created by mutation, are important for the understanding of many biological processes. However, the causes of interspecific variation in mutational parameters and the extent to which they vary within species remain largely unknown.
Which is a fancy way to say "We have no idea." There are some recent attempts that use the extreme value theory, but so far I have not seen anything meaningful in terms of numbers. Leaving this issue aside, for a beneficial mutation to be transmitted to offspring in multicellular/sexual organisms (where we find complex organs such as eyes), it would have to occur in germline cells, not just inside somatic cells. There are additional constraints and risks associated with germline mutations, an important one being that a significant number of mutations turn out to be harmful/lethal (current estimates are that 12% of all germline mutations are lethal), making it very unlikely that organisms that would have developed a beneficial mutation in their eye would survive to reproductive age to transmit their advantage to the next generation. (This is a serious stumbling block against evolution in general, not just eye evolution). Besides, we have to remember that sexual organisms inherit one copy of each gene from each parent, and for a beneficial mutation to stabilize in the population, both copies of the gene would likely have to have it. The likelihood of numerous such "mirror" mutations, as required by the model in the article discussed here, is beyond any shred of credibility. Not to mention the fact that there is overwhelming evidence that mutations remove, restrict or damage genetic mutation, rather than adding to it.
Furthermore, even assuming such beneficial mutations happened, and they were somehow passed down to the next generation, one would have to wonder at the incredible amount of environmental shifts required to select individuals with these mutations at each step, so that they had a survival advantage over the rest of the population, not once, not twice, but an incredible number of times.
In this context, to say the eye can evolve in the manner the Swedish authors above suggested, is similar to suggesting that one could make $1 million by gambling in Vegas, starting with only $1, if one had enough time and could ignore the losses. In real life, though, we cannot ignore the losses.