Is there such a thing as destiny? How resilient are outcomes to changed starting conditions?
This was the question that Stephen Jay Gould asked in his 1989 book Wonderful Life. If we travelled back in time to the Precambrian period before animals were a thing and restarted the tape of life, the kind of creatures that would evolve would be very different to what we have now. Maybe while you’re back there you step on a worm that turns out to be your ancestor, and voila, no humans. Think of it as an evolutionary Butterfly Effect.
In 2003, Simon Conway Morris published Life’s Solution, in which he made the opposite argument. Because of the pervasiveness of convergent evolution, the outcome is preordained. Flight has evolved multiple times in vertebrates: Birds fly, bats fly, pterodactyls flew. No matter how many times we go back to the Precambrian and trample the local primitive wildlife, flying will evolve.
Because I’m interested in evolutionary theory and because at the time I was at the same Cambridge college than Conway Morris, I read his book, but I don’t remember much. That’s because apart from its central thesis, it consists of a long and thorough list of examples for convergent evolution.
Jonathon B. Losos’ Improbable Destinies is different. It asks the same question than Gould and Conway Morris did and their views get a fair hearing. What has changed since their books appeared is that we have more data.
We still can’t go back in time, but we can and have run evolution experiments where bacterial populations are subjected to selection pressures over thousands of generations. The results suggest that starting conditions make a big difference to the way the bacteria evolve.
An orthogonal approach is to study how geographically isolated animal populations evolve. Again, while convergent evolution is pervasive, there are examples of unique adaptations. In Australia, the wombat is basically a convergently evolved groundhog but the kangaroo is unique.
Overall, Losos’ book is a satisfying summary of developments in one of the central questions in evolution over the last 40 years. It doesn’t provide definite answers but offers a roadmap how we may be able to get them. The writing is good and I like the illustrations too.
I still wonder: How transferable are the insights gained from studying the role of destiny from evolution to other areas? For example, Philip Tetlock (his book Superforecasters is excellent) argues that it is valuable to think about historical counterfactuals. Would Hitler not existing have prevented Nazi Germany? Maybe or maybe not, but data is lacking either way. Could it be that the methods biologists have used will also prove useful to the historians?
Nehaveigur 