Throughout history there have been many other examples, similar to that of Haeckel, Huxley and the cell, where a key piece of a particular scientific puzzle was beyond the understanding of the age.

The basic structure of proteins is quite simple: they are formed by hooking together in a chain discrete subunits called amino acids.

In the abstract, it might be tempting to imagine that irreducible complexity simply requires multiple simultaneous mutations - that evolution might be far chancier than we thought, but still possible. Such an appeal to brute luck can never be refuted... Luck is metaphysical speculation; scientific explanations invoke causes.

In private many scientists admit that science has no explanation for the beginning of life... Darwin never imagined the exquisitely profound complexity that exists even at the most basic levels of life.

The theory of undirected evolution is already dead, but the work of science continues.

Proteins are the machinery of living tissue that builds the structures and carries out the chemical reactions necessary for life.

As can be seen even by this limited number of examples proteins carry out amazingly diverse functions.