Over at Adaptive Complexity, the sesquicentennial celebration of the publication of Darwin's On the Origin of Species is rocking on with 30 Days of Evolution Blogging. From his position of extreme geographical proximity, Mike, abetted by our fearless leader, asked your friendly neighborhood Rugbyologist to contribute.

It is well-known that I dig on evolutionary theory (as well as BBQ and pie). But, come on. The 150th anniversary? The 200th birthday?

HUZZA! The occurrence of an arbitrary time unit with base 10 aesthetic appeal! HUZZA!

How am I supposed to take 150&200 seriously? They aren't even primes (149, 151,&199 are), and they can forget about the Fibonacci sequence (like 144&233).

And, the 150th anniversary of what? Darwin announced Wallace and his theory of natural selection to the Linnaean Society on 1 July 1958. If Darwin hadn't published On the Origin of Species on 24 November 1859 after his 50th birthday, we'd never have had the chance to shoe-horn the 150th&200th anniversaries together to great fanfare.

You may have noticed that 2009 is the 151st (prime) anniversary of Darwin's Linnaean Society presentation. You might think, "Now, that is an arbitraty time unit a Rugbyologist can get behind." Sure, as long as we ignore the fact that Darwin came up with natural selction in 1838. The year 1858 simply commemorates the year that a whippersnapper of a naturalist named Alfred Wallace came so close to stealing Darwin's thunder that Lyell finally managed to get his buddy Chuck off his ass and in front of an audience.

Then, obviously moved by my stinging refutation, Mike started to cry. So, in the spirit of further numerical abuse and ending the tears of grown men, let's take a look at how evolution has done capturing the hearts and minds of the American public over the last 151 years.

Starting in 1982, Gallup has been polling folks on their beliefs about evolution.
At first glance, this poll shows that evolution (spring green) is not gaining ground on creationism (puke green) or intelligent design (forest green). You may view this result with either glee or dismay, depending on which side your toast is buttered. In 1982, 44% of Americans thought the statement "God created man in present form" best represented their "views on the origins and development of human beings." In 2008, 44% of Americans also picked "God created man in present form." The 27-year average was 45% (+/- 1%).

In that context of a 151 year debate, 27 years is a relatively short term view. The high temporal resolution of the Gallup poll (1997/1999/2001&2006/2007/2008) says nothing about long term patterns. Wasn't creationism even more common at one point? You know, before Darwin?

The short term view looks bleak for evolution proponents. What about the long view? Let's put on our Hari Seldon hats and try to use made-up math to predict the trajectory of society.

In 1860, the population of the United States was approximately 31 million. In 2010, the population will be approximately 310 million. To make the math easy (hey, I'm a biologist here) let's assume that on 30 June 1858, 100% of Americans would have picked "God created man in present form"? From Gallup, we know that in 2008 44% of Americans (~1.36 million) espoused the creationist idea. The graph below (The First 150 Years) represents our assumption (1858 datum) and the Gallup data (1982-2008).
From the data and our assumptions, we can create an exponential growth model of changes in both total US population (red) and US creationist population (blue),

which allows us to predict the creationist proportion of the population (blue line) in any given year (rsq = 0.98).



In fact, it allows us to project the populations (blue line) into the future (ignoring upper limits to population size).


Not only does this approach reassure evolution advocates that they are not stuck in the mud, it predicts the decline creationist thinking. It should only take another 970 years, when the US population is 91 trillion or so, for creationism to disappear. Be patient!

Not good enough for you? Let's validate a different model based on the poor fit of the 1982 datum to the exponential curve. A third order polynomial fits the 1858 assumption and Gallup data even better than the exponential growth model (rsq = 0.99). This is the curve evolution advocates have been waiting for. It predicts the demise of creationist thinking by 2050.

Interestingly, the shape of this curve reflects the conventional wisdom that fundamentalist thinking as been on the rise in the United States during the 20th Century. Since this fits both my preconceived notions and my hopes for the future, I declare this third order polynomial an accurate representation of reality. According to this equation creationists, you have about 40 years to change your mind, or else.

One benefit of such models is that they can highlight weaknesses in the interpretation drawn from a narrow data set, such as the Gallup poll. Given what we know of human behavior, it is unreasonable to expect large changes in attitude toward questions such as the origins of human life over relatively only 1-2 generations. It also fits human nature to expect that the rare a belief becomes, the harder it will become to change the mind of that portion of the population, which is reflected in the exponential model.

The other benefit of these models is that they make predictions, no matter how flippantly they have been constructed. The exponential growth based model that I have presented here predicts that in 2018 the Gallup poll will find 42% of Americans (population ~360 million) will pick "God created man in present form". In 2048, it will be 35%. The polynomial model predicts less than 40% in 2018 and that no one will agree with "God created man in present form" by 2050. See you in a decade. I'll try to resist the urge to say, "I told you so."