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problems for darwin : lecture three

irreducible complexity

Irreducible complexity is the idea that some organs, such as eyes, are so complex that they could not have arisen in the piecemeal, one mutation at a time, fashion required by natural selection. This is because ‘half an eye provides no reproductive advantage’, and without the pressure of natural selection the necessary sequence of mutations would not occur before the end of time.

Irreducible complexity was, initially, the centerpiece of the creationist attack on Darwin’s theory of evolution by natural selection. The claim was that eyes had to arise as a complete piece. That is as a work of the creator.

The fossil record shows primitive eyes appearing and becoming more complex over time, and this has been the Darwinian counter to the claim of irreducible complexity.

Darwinians say that poor vision is an advantage over no vision at all. Indeed, they say, it is possible that something essential for the development of a complex structure may have initially arisen, as the result of natural selection, with a quite different function (exaptation). Feathers, they say, initially developed as an aid to heat regulation and were later exapted to their function as aids to flight.

According to Darwin’s theory of evolution by natural selection, complexity arises as natural selection operates to adapt primitive organs. Natural selection acts as a pruning force, in this case pruning to improve.

One flaw in this argument, and it may be a fatal one, comes from the fact that eyes have a discrete ontogenesis. The right genes must be activated at the right time and for the right time in the embryo for an eye to develop.

Darwin’s theory provides no account of ontogenesis (embryonic development) when this is central to the development of complex organs.

Another flaw in the Darwinian response to the problem of irreducible complexity lies in the impossibility of a new gene, one that codes for a new protein, arising by chance.

Assume, for the sake of argument (and this is just by way of demonstration), that a primitive eye requires an ancestor to develop one new gene, just one small gene, say 1,000 bases long. (I know the number of bases should be a multiple of three, but the math is easier this way and nothing important is lost)

While the ancestor has no eye this gene does not exist. It needs to arise by mutation according to Darwin’s theory of evolution by natural selection.

Assume now that a 1,000 base sequence of DNA has been inserted in just the right place and it will be activated at the right time for the right time in the embryo. Each of these things is incredibly unlikely to arise by chance, but, for the sake of argument, assume that they have happened.

This initial sequence of 1,000 bases is essentially random so far as the required ‘primitive eye’ gene is concerned. That is, each of the 1,000 locations is occupied by one of 4 bases so by chance about one-quarter of the bases will be ‘correct’. However, unless all 1,000 bases are correct the required protein is not produced, and until the required protein is produced there is no primitive eye. No eye, no competitive advantage, no natural selection.

How many attempts will it take to get all the bases (answers) correct?

Let’s be generous and assume that the correct sequence is found after only 1% of the possibilities have been tried.

There are 4x4x4……..x4x4 (4 multiplied by itself 1,000 times) possibilities. This is a reasonably large number. One percent of it is also a reasonably large number, a little larger than 1 followed by 600 zeroes. The universe is perhaps 14 billion years old, or something less than 1 followed by 19 zeroes seconds. This first gene just isn’t going to arise by chance. A miracle is needed.

Matters are made worse by the reliance on mutations, which will not occur in every offspring of every generation.

The problem is entirely analogous to imagining a student required to answer 1,000 multi-choice questions correctly, without knowing the questions.

This is the fatal flaw in the claim that Darwin’s theory of evolution by natural selection is a complete explanation. It can not get started. Once the first primitive eye forms, then natural selection is a plausible way for that eye to develop into a more complex structure.

But if that first eye requires a new gene, that can’t arise by natural selection.

Possibly, it may be that the gene required for a primitive eye is an old, unused gene for which a new use is found. But that can’t always be the case. If it were all animals and plants would be based on the same genes, and these would be the genes that arose spontaneously on the first day life appeared on this planet (and we are back to a Creator).

The insurmountable problem for Darwinians is that the gradual process on which the theory relies is not how evolutionary change always begins. Sometimes it must begin discretely, with a jump, before natural selection can operate.

The evolution of the eye was a problem recognized by Darwin. He also saw a similar problem with the evolution of the wing.

There seems to be general agreement that life began underwater, and it may well be that flippers (or even gills) can be seen as very primitive wings. But flippers became limbs as animal life invaded dry land, and it seems that limbs became wings.

There are lots of ideas around as to how “half a wing” could provide a reproductive advantage. The common theme is called ‘exaptation', where physical structures that initially had one purpose come to have another purpose (millions of years) later.

This is a powerful idea. For example flapping half a wing could make it easier to climb trees!

If we accept, once again purely for the sake of argument, that the first eye gene has arisen by mutation in some animal, what happens next?

The short answer is that that animal dies before he or she is old enough to reproduce. Death before reproductive maturity is the norm in the animal kingdom.

Even if that animal does live and has more offspring than the average, the probability is still that all of them will die before reproducing.

The first animal with a primitive eye has another problem, as even if he or she produces offspring and this continues for a number of generations death is lumpy, not homogenous, in populations. For example, the offspring are all likely to live within a relatively small area which could be devastated by a local natural disaster, or by the entry of a predator, or by an illness.

There is a category of adaptation which, at first, seems to pose problems for the Darwinian. This is the “mimics”. An example is the stick insect which is protected from predators (birds) by a combination of camouflage and immobility.

Although it is possible to use the argument that the first “mimic” gene could not have arisen by chance, it is equally possible that “mimic” is not a new single gene property at all. It may be an acquired characteristic transmitted epigenetically or it may be a multi-gene phenomenon. Camouflage and behavior are relative properties. They are not new properties. A stick insect only needs to be better camouflaged and more still than its neighbor. Then the neighbor gets eaten. If this is true then stick insects are the result of a breeding program, a true example of natural selection in action.

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