From Sarah Zhang at the Atlantic:
As you read this article, the cells in your body are dividing and the DNA in them is being copied, letter by letter. So long is the human genome—more than 3 billion letters—that even an astonishingly low error rate of one in many million letters could amount to 10 new mutations every time a cell divides.
Oh, perhaps you’re also catching some sun (ultraviolet rays) while you read this, or enjoying a beer (alcohol), or have recently been high in the atmosphere on an airplane (cosmic rays). Congratulations, you’ve given yourself even more mutations. In a typical day, scientists estimate, the 37 trillion cells in your body will accumulate trillions of new mutations.More.
We are told that “Evolution has built in a formidable number of safety nets.” It takes considerable faith in the powers of Darwinian evolution (natural selection acting on random mutations) to accept such a statement at face value, given the scale and complexity. But we suspect that Atlantic readers are over-represented in the sample of such people.
See also: Eugene Koonin on how CRISPR is leading to conceptual shifts in evolutionary biology. Koonin: Furthermore, different biological systems that function by genome manipulation appear to have evolved convergently from unrelated MGE.