Quote of the Day: eric on Evolution and Compound Interest

This is a really important point that is well put by eric. It goes a long way to expaining why people just don't get the shift from supposed micro-evolution to macro-evolution:

My feeling is it has more to do with innumeracy and particularly, the fact that human intuition in really bad at estimating compound/geometric change. Most people will significantly underestimate how much money their bank account can produce over a lifetime via compound interest. I start with $100 and a 1% daily interest rate. Tomorrow, it's 1.01*$100 = $101. The day after, it will be 1.01*$101, not just adding a dollar, which is the calculation our intuition will naturally tend to do. The difference between the simpler 'add a dollar' intuitive estimate and the actual compound total gets larger over time.

Evolution is a nearly identical form of compound change over time. A parent organism will have a genetically mutated daughter. The granddaughter organism, like tomorrow's interest, will be derived from the already-mutated daughter; it mutates from $101 to some new state, it doesn't mutate from the original $100 to some new state. Thus, like with compound interest, our naïve or innumerate estimate of what evolution can accomplish is likely to drastically underestimate what it can really accomplish - and like with compound interest, the more cycles the process goes through, the bigger our mistake/underestimation is likely to be. Billions of years of microorganism generations is a lot of cycles. :)

What this means in terms of educating the public about evolution is that (a) we should not be surprised or derogatory towards people who are skeptical that evolution could produce the variety of organisms we see in the amount of time that has passed, because (b) their skepticism at least in part derives from a common human bias/fallacy that has little to do with religion. Its pretty normal for someone without the requisite education to underestimate the power of things like compound change and exponential growth, and that mistake has nothing to do with what religious beliefs you were indoctrinated into during childhood.