What can Sudoku teach us about ecology and evolution?

Evolution is creeping into several different aspects of ecology. The latest buzz is all about integrating ecology and evolution. Perhaps you’ve heard of the  latest research trends in eco-evolutionary dynamics or community phylogenetics?

Theodosius Dobzhansky famously stated that “Nothing in biology makes sense except in the light of evolution“. This claim is undoubtedly true, but I’ve recently found myself wondering whether our obsession with evolution is actually clouding our ability to do good ecological research.

Please don’t misunderstand me, I am not implying that evolution is not important in explaining patterns in nature, nor am I suggesting that we should disregard evolutionary explanations for these patterns. Instead, I believe that in order to gain a deeper understanding of ecology, we should perhaps partially blind our views using “evolution blinkers”. In fact, I’d even be so bold as to claim that unless we blind ourselves to evolution, we will never be able to fully grasp the true nature of ecological processes. Unifying ecology and evolution might actual limit our ability to build ecology as a science.

Richard Feynman used a useful chess analogy to explain how physics works. I’ll borrow this style of argument to explain my stance on ecology and evolution. However, since chess is too complicated for my liking, I’ll use an even simpler game: Sudoku.

I’m sure most of us are familiar with the game of Sudoku, a game where 81 cells are arranged in a 9 by 9 grid and filled with the integers 1 through 9. If you page through a book of Sudoku puzzles – or, more precisely, skip to the back to look at the solutions to these puzzles – you’ll immediately notice that each of the grids are filled with different combinations and sequences of numbers. Each Sodoku puzzle has a unique solution; a distinct endpoint. The one-of-a-kind pattern unique to that Sodoku grid.

Now imagine an alien who, on landing on earth, discovers a book of Sudoku puzzles. It notices how large parts of the human population are captivated by cracking these cyphers. The alien, assuming that solving the Sudoku code will unlock some fundamental secret to the universe, sets out to understand the ‘true nature’ of the puzzle.

By examining the book, the alien notices that it is the mostly empty starting grids (with a few starting values already provided) and the completed solutions at the back of the book.

Since it is unfamiliar with the inner workings of Sudoku, it decides to unravel the underlying mechanism of Sudoku using purpose-built multivariate statistics. After applying these complex tools and tricks, our alien investigator discovers that every unique endpoint is strongly correlated to the distinct starting values. So strongly, in fact, that most of the variation in the endpoint patterns can be explained by the starting conditions.

The alien has figured it out! Its results show, without a shadow of a doubt (yes, P < 0.05!), that the end point of a solved Sudoku puzzle can mostly be attributed to its starting conditions.

In this analogy, each unique pattern for a solved Sodoku puzzle is akin to observable patterns in nature; whether it is the number of birds in a tropical forest, the relative abundance of insects along a hillside or even the global distribution of grasslands across the planet. The unique starting conditions of the Sudoku puzzle can be likened to historical processes, such as evolution, speciation, and historical colonisation.

There are, for instance, phylogenetic explanations for global bird species richness, evolutionary explanations for how insect’s thermal niches change with altitude and biogeographical explanations for how historical climate determined the extents of vegetation biomes cross the planet.

I’d be willing to wager that most sophisticated techniques will manage to find an evolutionary explanation for almost any contemporary pattern in nature if the researchers search hard enough. In this sense, it is exactly like the alien with its fictional Sodoku analysis: the end conditions (or the patterns in nature) are strongly correlated to the starting conditions (historical evolutionary events).

Theodosius Dobzhansky seems to be right: it is all about evolution! Nothing, whether it is in Sudoku or in nature, makes sense without first considering its origin story.

However, anyone who has ever struggled to complete a Soduku puzzle can tell you that the appeal of the game is not about realising that the end configuration is determined by the starting conditions. Unlike the statistically-proficient alien, Sudoku enthusiasts understand that it is the processes linking these starting conditions to the completed grid that make Sudoku one of the most popular puzzles on the planet!

A Sudoku grid is made up of nine quadrats of 9 by 9 cells. The rules state that each of these quadrats must contain all the numbers 1 through 9. Moreover, each row and each column on the full grid must also contain the numbers 1 through 9. It is these three simple rules that have captured the attention of that guy on the train during his daily commute, the old lady passing the time on a Sunday afternoon and even an ecologist trying to make a point on his poorly-maintained blog!

In Sudoku, the end configuration is undoubtable “caused” by the starting conditions, but it is the simple rules of arranging numbers that capture its essence.

Ecology is the same. Patterns in nature are undoubtedly determined by evolution. However, we shouldn’t just rest on our laurels because evolutionary processes explain most of the contemporary patterns in nature. Instead, this knowledge should inspire us to find the elegant ecological rules that could perhaps capture the “essence” of nature in the same way simple rules capture the “essence” of Sudoku.

I think it is the easy option to just attribute every pattern in nature to evolutionary processes. Of course, such attribution will generally provide exceptionally accurate descriptions of reality. However, I also worry that by stopping there, we are no different to Soduku-researching extraterrestrials. If we just concede that, “it’s all evolution”, we could perhaps miss the actual essence of nature; those handful of simple, elegant rules that could captivate us for hours on end.


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