Tag Archives: paleontology

It’s a Wonderful Life

I’ve sometimes been asked whether the idea of the LTEE was inspired by Stephen Jay Gould’s book, Wonderful Life. In this bestseller, Gould put forward the idea of “replaying” evolution to explore the idea of whether evolution is repeatable. He wrote (page 48): “I call this experiment ‘replaying life’s tape.’ You press the rewind button and, making sure you thoroughly erase everything that actually happened, go back to any time and place in the past—say, to the seas of the Burgess Shale. Then let the tape run again and see if the repetition looks at all like the original.”  However, Gould then went on to say: “The bad news is we can’t possibly perform the experiment.”

Gould (1941-2002) was a paleontologist as well as an historian of science and prolific author, and he had in mind replaying life’s tape on a planetary scale over millions of years. The Burgess Shale is a geological formation in western Canada that contains fossils from about 500 million years ago. The fossils include exceptionally well-preserved early animals, many of which have body plans that are unlike any modern animals. Building on his thought experiment of replaying life’s tape, Gould pondered the potential outcomes: “If each replay strongly resembles life’s actual pathway, then we must conclude that what really happened pretty much had to occur. But suppose that the experimental versions all yield sensible results strikingly different from the actual history of life? What could we then say about the predictability of self-conscious intelligence? or of mammals?”

Of course, Gould’s experiment is impossible at a paleo-planetary scale. But at a more modest scale, one of the main goals of the LTEE is to study the repeatability of evolution. And so, I often quote from Wonderful Life when I’m giving talks about the experiment. Thus, it’s only natural that someone might wonder if Gould’s book had inspired me to start the LTEE.

In fact, though, Wonderful Life was published in 1989—a year after the LTEE began. I think I first heard about it when Mike Travisano shared some passages with me that were relevant to a paper we were writing on the roles of adaptation, chance, and history in evolution.

So, while Gould and I were thinking about similar issues, we were imagining them at vastly different scales. It’s one of the fascinating aspects of evolution that these broad categories of causality—adaptation by natural selection, chance events from mutations to asteroid impacts, and the effects of past history on future opportunities—play out at these different scales.

I was lucky to meet Gould and discuss these issues with him several years later, as I’ll describe in a future post.



Filed under Old Books, Science

Favorite Examples of Evolution

When the cold bites, When the review stings, When the news is sad, I simply remember these evolving things, And then I don’t feel so bad! — with apologies to Rodgers and Hammerstein

Over on Twitter, the biology students from George Jenkins High School in Lakeland, Florida, asked me and many others: “What’s your favorite example of evolution?”  There are so many fascinating examples that it’s hard for me to pick just one. So, here are half a dozen examples that are among my favorites.

  • The discovery by Neil Shubin and colleagues of Tiktaalik, an extinct fish (pictured below) from the Devonian that was poised to give rise to terrestrial vertebrates. You can read about this work in Shubin’s award-winning book, Your Inner Fish, which was also made into a PBS show.
  • The discovery by Svante Pääbo and colleagues of the Denisovans, an extinct lineage of humans, based on sequencing a complete genome from the finger bone of a girl who lived tens of thousands of years ago.
  • The analysis by Tami Lieberman, Roy Kishony, and colleagues of the genetic adaptation of an opportunistic species of bacteria to the lungs of patients with cystic fibrosis. I’ve blogged about that paper here.
  • Here’s one from the long-term experiment in my own lab — the evolution of the ability to use citrate that arose in just one of the 12 populations and after more than 30,000 generations. There are nice summaries of this work in Carl Zimmer’s blog here and here.
  • A study by Hod Lipson and Jordan Pollack on the evolution of robots. I remember hearing about this paper and being shocked: “Wait a second. Robots are expensive, and most things go extinct during evolution. How could they even afford do this?” I had to read the paper to realize they were evolving virtual robots in a physical simulation of the real world. They then built and tested the winners in the physical world. And indeed, the robots worked as they had evolved to do.
  • Applying the mechanisms of evolution to artificial systems is a fascinating approach useful for both biology and engineering. One of my favorite basic-science uses of this approach was a paper where we used digital organisms – computer programs that self-replicate, mutate, and compete for resources – to show how very complex functions could evolve if simpler functions were favored along the way. These simpler functions provided building blocks for the more complex functions, illustrating how evolution works by tinkering and borrowing already existing structures and functions and using them in new ways. Incidentally, this work involved collaboration between a computer scientist (Charles Ofria), a philosopher (Rob Pennock), a physicist (Chris Adami), and a biologist (me).

Readers: Please feel free to add your own favorite examples of evolution in the comments section below.

[The picture below shows the Tiktaalik fossil discovered by Neil Shubin and colleagues.  It was posted on Wikipedia by Eduard Solà, and it is shown here under the indicated Creative Commons license.] Tiktaalik


Filed under Education, Science