Evidence of evolution from genetics

The argument

Genetics provides some of the most powerful confirmation of evolution, because the genetic code reveals the relationships between species with a precision the visible world cannot. All life on Earth uses the same fundamental molecular machinery — the same DNA, the same genetic code translating it into proteins — a deep unity that points to a single common origin. More tellingly, when biologists compare the genomes of different organisms, the degree of similarity tracks exactly the branching pattern of descent that evolution predicts: humans share the overwhelming majority of their DNA with chimpanzees, somewhat less with other mammals, less again with more distant relatives, producing a nested family tree that matches the one drawn from anatomy and fossils. The argument is reinforced by features that only shared ancestry can explain. Genomes are littered with non-functional remnants — broken 'pseudogenes', and ancient viral sequences inserted into DNA long ago — and the same defunct genes and viral scars appear at the same positions in related species. Humans and other primates, for instance, share an identical broken gene for making vitamin C, disabled by the same mutation; this makes sense only if they inherited the broken gene from a common ancestor in which it first failed. No designer would install the same precise errors in the same places. Genetics also lets evolution be watched directly, as mutations arise and spread and as DNA evidence reconstructs lineages and confirms predictions about which species are most closely related. The molecular record agrees with every other line of evidence and adds detail none of them could supply. Because genetics provides this independent and precise confirmation of common descent, this argument holds, the theory of evolution by natural selection is correct.

Premises

Counter-arguments

The main objection raised against this argument is not to the data but to one inferential step: the claim that shared features, especially shared 'broken' genes and viral insertions, can only be explained by common descent. Proponents of common design reply that a single designer reusing the same working molecular toolkit could also produce a unified genetic code and nested similarities, and that shared sequence need not imply shared ancestry. They also point out that some DNA once classed as non-functional 'junk' — including certain pseudogenes and endogenous retroviral sequences — has since been found to have regulatory or other functions, which they argue weakens the 'same useless error in the same place' premise. Defenders of the argument regard these replies as far weaker than the evidence, but critics note the inference to common descent does the real work and is where any challenge must be aimed; the raw similarity data alone is, in principle, compatible with more than one explanation, so the argument's force depends on ruling those alternatives out rather than on the sequence comparisons by themselves.

Rejecting the premises

[Rejecting P2] Critics from a common-design view argue shared pseudogenes and viral insertions could reflect a reused design or as-yet-unrecognised function rather than inheritance, and note some 'non-functional' remnants have since been found to have roles, contesting the 'only ancestry explains it' step. [Rejecting C] Because the similarity data is what needs interpreting, the conclusion rests on the inference to common descent; critics argue that inference, not the sequencing itself, is where the argument must be defended.

Further reading

https://www.nature.com/articles/hdy200814 https://www.pnas.org/content/113/28/7774 https://muslimskeptic.com/2019/07/14/the-sparsity-of-99-evaluating-human-chimp-genetic-similarity/