Complexity_ A Guided Tour - Melanie Mitchell [34]
Turing also visited the Institute for Advanced Study and was offered a membership but decided to return to England. During World War II, he became part of a top-secret effort by the British government to break the so-called Enigma cipher that was being used by the German navy to encrypt communications. Using his expertise in logic and statistics, as well as progress in electronic computing, he took the lead in developing code-breaking machines that were eventually able to decrypt almost all Enigma communications. This gave Britain a great advantage in its fight against Germany and arguably was a key factor in the eventual defeat of the Nazis.
After the war, Turing participated in the development of one of the first programmable electronic computers (stemming from the idea of his universal Turing machine), at Manchester University. His interests returned to questions about how the brain and body “compute,” and he studied neurology and physiology, did influential work on the theory of developmental biology, and wrote about the possibility of intelligent computers. However, his personal life presented a problem to the mores of the day: he did not attempt to hide his homosexuality. Homosexuality was illegal in 1950s Britain; Turing was arrested for actively pursuing relationships with men and was sentenced to drug “therapy” to treat his “condition.” He also lost his government security clearance. These events may have contributed to his probable suicide in 1954. Ironically, whereas Gödel starved himself to avoid being (as he believed) poisoned, Turing died from eating a poisoned (cyanide-laced) apple. He was only 41.
CHAPTER 5
Evolution
All great truths begin as blasphemies.
—George Bernard Shaw, Annajanska, The Bolshevik Empress
THE SECOND LAW OF THERMODYNAMICS states that the total entropy of an isolated system will always increase until it reaches its maximum value. Everyone knows this instinctively—it happens not only in our understanding of science, but also in our daily lives, and is ingrained in humans’ conceptions of history and in our art, literature, and religions. The Buddha tells us that “Subject to decay are all compounded things.” The Old Testament prophet Isaiah foretells that “The earth shall wax old like a garment.” Shakespeare asks,
O! how shall summer’s honey breath hold out,
Against the wrackful siege of battering days,
When rocks impregnable are not so stout,
Nor gates of steel so strong but Time decays?
It is a gloomy message, this inexorable march toward maximum entropy. But nature gives us a singular counterexample: Life. By anyone’s measure, living systems are complex—they exist somewhere in the middle ground between order and disorder. According to our intuitions, over the long history of life, living systems have become vastly more complex and intricate rather than more disordered and entropic.
We know that to decrease entropy, work must be done. Who or what is doing the work of creating and maintaining living systems and making them more complex? Some of the world’s religions propose that a deity is responsible, but in the mid-1800s, Charles Darwin proposed that instead, the history of life has resulted from the invisible hand of evolution via natural selection.
No idea in science has been more threatening to humans’ conceptions about themselves than Darwin’s theory of evolution; it arguably has been the most controversial idea in the history of science. But it is also one of the best ideas. The philosopher Daniel Dennett strongly affirms this:
If I were to give an award for the single best idea anyone has ever had, I’d give it to Darwin, ahead of Newton and Einstein and everyone else. In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning, and purpose with the realm of space and time, cause and effect, mechanism and physical law.
This chapter sketches the history and main ideas of Darwinian evolution and how it produces organization and adaptation. Concepts from evolutionary theory will come up again and again in the remainder