The Nuts and Bolts of Evolution

Mechanisms and molecules have been preserved in bacteria, fungi, plants, and animals, essentially intact through billions of years of Darwinian evolution. 

Perhaps the first question we should ask is why any gene changes at all. Would it not be better from the point of view of the gene itself to be copied 

In the cells that are used in the lifetime of the individual but are not passed on to descendants, which are called somatic cells, the error rate is higher, but stiU impressively small. 

The body has to make the same compromises that a factory making a specialized and complicated instrument has to make the master copy of the design needs to be carefully protected from damage, and if copied for use in another factory it needs to be copied with meticulous accuracy to avoid errors. 

The more routine copies that are used for the actual manufacturing need to be accurate as well, as it is not good to produce large quantities of defective instruments, but a certain low proportion can be tolerated. 

---

The geneticist Richard Levontine has been quoted as describing population genetics as the auto-mechanics of evolution because most users do not like to be bothered with the nuts and bolts of it. The derivations are laborious and lead to inelegant solutions. The same can be said of the relationship between most biochemists and physiologists and the details of kinetic derivations. Such disenchantment with the field under discussion... 

Thus, to go back to the bombardier beetle and the human eye, the question is whether the numerous anatomical changes can be accounted for by many small mutations. The frustrating answer is that we can t tell. Both the bombardier beetle s defensive apparatus and the vertebrate eye contain so many molecular components (on the order of tens of thousands of different types of molecules) that listing them— and speculating on the mutations that might have produced them—is currently impossible. Too many of the nuts and bolts (and screws, motor parts, handlebars, and so on) are unaccounted for. For us to debate whether Darwinian evolution could produce such large structures is like nineteenth century scientists debating whether cells could arise spontaneously. Such debates are fruitless because not all the components are known. 

---