Bayesian thinking and evolution

Coin Collection
OK, I need a fair coin… Any volunteers? I’ll need references. (Photo credit: flash2)

A quick post, today, as pastoral, camp, and festival work is thick! But I read a nice article last night and thought it worth sharing.

It came in my e-mail, through my “Nota Bene” subscription with the Discovery Institute: “Understanding Bayesian Analysis, the Evolution Skeptic’s Friend”

I’ve mentioned the Bayesian approach to probabilities before (here, too), and this article–explaining how natural it is to think in a Bayesian manner and how truly reasonable and rational it is to doubt so many of the claims of neo-Darwinian apostles–does a nice job of giving the feel of it.

My favorite way of summing up Bayesian thinking is to talk about the hypothetical “fair coin” we always talk about when teaching probability. A coin doesn’t remember the results of its previous flip results, so if a truly fair coin is tossed four times and each time “Heads” is the result, what is the probability that a “Heads” will result again?  The answer–assuming a truly fair coin–is 50% (or, as some would say, 50-50). While some want to say, “‘Tails’ has gotta come up after all those heads in a row,” if it is truly a fair coin then, no, the odds are still even. And, sometimes to stress the power of independent trials, the teacher will exaggerate: “What if the fair coin produced a ‘Heads’ 100 times in a row, would that make any difference?” The correct answer is, “No–if it is truly a fair coin, then on toss 101 it is still 50-50, and you have even odds that you will receive a ‘Heads’ or a ‘Tails.'”  Yet, it is only in the hypothetical world of the theoretical math text book that a “truly fair coin” will produce a “Heads” result 100 times in a row (or, perhaps a world somewhere in Max Tegmark’s Ensemble).  Here in the real world, if you see someone call it a “fair coin” and it produces 100 “Heads” in a row, you start to think (actually, you began to think long ago) that the fix is in and something is fishy in Coin-Flippy Town. Consequently, you ignore the claim of “fair coin” and begin hedging your estimated probabilities based on what experience tells you: This coin favors heads.

That is Bayesian thinking. Actually, Bayesian probability gives a methodical means of bringing experience-based levels of confidence into the calculation of probabilities, but what I’m calling “Bayesian thinking” is at the heart of that approach. And the article from Evolution News and Views does a great job, IMHO, of showing how Bayesian thinking is natural to us and how it is the right way to consider the claims of neo-Darwinian apostles. Check it out, and, if you want to read more, you can click through to my older posts about how Bayesian probability analysis has been used to analyze the likelihood of alien life and intelligence in the universe and even whether or not God exists.

3 thoughts on “Bayesian thinking and evolution

  1. John Wheeler (Johanan Rakkav)

    Just from your summary, I think to myself: So much for the sometimes-made claim that human beings weren’t evolved to think rationally (which, perversely, is used in the next breath to argue that belief in “goo-to-you-by-way-of-the-zoo” evolution is rational). I look forward to delving into this further.

  2. TeapotTempest

    In Balzer’s article he quotes Dr. Sagan as saying, “They also tend to be less than assiduous in exposing themselves to the evidence. Evidence has little to do with it. What they wish to be true, they believe is true.” The problem is, like most narcissistic scientists and politicians, they accuse others of being guilty of the same thing THEY are guilty of doing.

    I remember as a child I used to have fun with a coin that always turned up heads… (until I was caught cheating). The coin had two heads. Evolutionists and Climate-change kooks do the same thing: they “adjust” and accept only data that fits what they believe to be true and consider anything else to the contrary as “outliers”. “What, you don’t believe man is making things warmer? You obviously don’t have the right information or are just too ignorant to understand the implications of global-warming.” Heads, I win. Heads, you lose. Simple.

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