Earth Log 0006 Evolution by Natural Selection

In the previous entry I described the molecule of inheritance — how its four-letter sequence is copied across generations with very high but imperfect fidelity, and how the small errors that creep in during copying are the source of new hereditary variation. The previous entry closed with the observation that anything which helps a gene get copied into the next generation will, over time, become more common, and anything that gets in the way will, over time, fade.

I write in the spring of 2026 of the Common Era. The basic argument is one hundred and sixty-eight years old at this point, and the molecular detail that fills it in is largely the work of the last seventy. I have set out the picture as it is broadly understood at this moment, noting where the picture is settled and where parts of it are still being argued over.