Biological life is far too complex to have arisen from chance

The argument

A central objection from critics of evolutionary theory is that living things display a degree of intricate, interdependent complexity that, they argue, undirected processes could not have produced. The living cell, on this view, is not a simple blob but a microscopic factory of staggering sophistication — packed with molecular machines, information-storage systems in DNA, error-correction mechanisms, and thousands of precisely coordinated chemical reactions, all working together. Critics contend that systems of this kind, in which many parts must be present and correctly arranged for the whole to function at all, point to design rather than to the accumulation of chance variations. The argument is often framed around the idea of 'irreducible complexity', associated with the biochemist Michael Behe, who argued that certain biological systems — such as the bacterial flagellum, a rotary motor of many interacting protein parts — would not work if any single component were removed. If the system confers no advantage until all its parts are in place, critics ask, how could natural selection, which can only preserve functional intermediate steps, have built it gradually? They extend the point to the apparent fine-tuning and engineering of organisms generally, arguing that the sheer, baffling complexity of life is more reasonably explained by an intelligent cause than by blind mechanism. Proponents of the theory respond that selection can co-opt and repurpose existing parts and build complexity by small steps, but critics of this argument answer that no such pathway has been convincingly demonstrated for the hardest cases, and that the intuition of design remains the more compelling explanation. Because the theory cannot, in their view, make sense of the baffling complexity of biological life, this argument holds, life is too complex to have arisen from chance, and the theory of evolution is flawed.

Premises

Counter-arguments

The mainstream scientific reply is that 'irreducible complexity' has been directly answered: the bacterial flagellum's components have known homologues serving other functions, such as the type III secretion system, showing parts can be co-opted, and evolution builds complex systems by repurposing, duplication and scaffolding that is later removed, so intermediate stages need not have the final function. Biologists note that 'too complex to have arisen by chance' mischaracterises natural selection, which is a non-random filter, not chance, and that 'no pathway has been demonstrated' is an argument from present ignorance rather than evidence for design. The complexity of cells is real but has documented evolutionary explanations.

Rejecting the premises

[Rejecting P2] 'Irreducible complexity' has been directly rebutted: flagellum components have homologues serving other functions (e.g. the type III secretion system), showing selection can co-opt parts and build via removable scaffolding. [Rejecting P3] 'No pathway has been demonstrated for the hardest cases' is an argument from present ignorance, not evidence for design, and mischaracterises selection, which is a non-random filter rather than chance.

Further reading

Support: https://www.discovery.org/f/45693/ https://www.discovery.org/f/45721/