TIL: Second-order Darwin machines

[timelets]

Second-order Darwin machines are systems within living organisms that themselves incorporate or deploy the same generate-test- regenerate principle.

One essential second-order Darwin machine is the human immune system. Since it cannot predict exactly which pathogens individuals will happen to meet in their lifetimes, especially as bacteria and viruses evolve so fast, it generates a massive array of possible antibodies. Only when the environment tests positive, when antibodies meet pathogens they can fit and therefore dis- arm, are they selected for massive short-term regeneration.

Another second-order Darwin machine is the human brain. Since evolution cannot predict in advance exactly what environments human brains will meet, brains begin by generating in infants more neural connections than they need, then testing them by experience, strengthening (regenerating) those interconnections that have been used, and killing off those that have not.

-- Brian Boyd, ibid.