by Greg Mayer
Several days ago, while walking to my car past a small patch of woods adjacent to the building where my office is, one of my students called to me from the woods. He has been working on various projects, and this year has been pretty much in charge of a project to monitor the abundance of an invasive exotic crayfish in a local pond. He was sitting on a chair in the middle of the woods, and as I approached him I noticed two bird feeders hanging in trees nearby. He explained that he was working on a lab for his animal behavior course, but had seen few or no birds that morning. Surveying the woods, I noticed how open it was because the canopy trees had not yet leafed out, and very few of the understory trees or shrubs had either. There were, however, quite a few flowering herbaceous plants, and, seeing how the birds were scarce, we took a look at the flowers. They were unevenly distributed over the forest floor, with large clumps or colonies here and there. We wondered about this– were there subtle habitat differences we could not immediately see that determined where the plants grew? Or perhaps they reproduced clonally, and each patch was where a successful individual had landed.
While I take some pride in my knowledge of local trees, forest herbs are not my forte. The student said he thought the plants nearest us, with white flowers and lobed, shamrock-like leaves, were bloodroot. He plucked one, and sure enough a reddish sap was evident in the stem. We looked around a bit more, and found some Trillium, too. About this time a graduate student who also works in my lab was walking down a path through the woods, and we called him over, and showed him the plants we’d found. I told the students about how this was a good time to be in the forest, because you see much further before the understory leafs out, allowing you to see the topography and the distribution of the big canopy trees at a glance, as well as the flowering herbs, some of which are ephemeral and will soon die back, but others of which will, after flowering early, keep their green leaves all season.
I mentioned to the students that I’d seen a great web post that morning about first contact with aliens (h/t: PZ), which stressed the likely lack of similarity and extreme technological disparity between us and interstellar travelers (“nuclear weapons [used by them] vs. sponges [which would be us]”), and how a binary code would be the way to communicate, although PZ noted they’d probably collect several specimens for the interstellar natural history museum before they figured out the sponges [that would be us] were sentient. The grad student suggested that it wouldn’t be that bad, since convergent evolution would insure that they had some basic similarities to us. I said I’m not so sure, and noted that George Gaylord Simpson, in his famous essay on the nonprevalence of humanoids (link might require subscription), had argued strongly that life elsewhere is decidedly unlikely to be familiar to us. We discussed what basic similarities there might be among life forms evolved completely independently. Bilateral symmetry? Common on earth, but how many times had it evolved independently here? Cephalization? There were some interesting cases of it evolving in primitively radial urchins. Carbon based? It beats silicon, but there was the Horta on Star Trek. The grad student recalled how Star Trek “explained” the prevalence of humanoids by having the “ancient humanoids” seed the galaxy with DNA that would lead to the evolution of humanoids. This, I noted, is no explanation at all, but it did show the Star Trek producers were aware of the thrust of Simpson’s critique.
We went on to note that there were ways of trying to distinguish independent from convergent origins. Shared, yet arbitrary, characteristics, such as the genetic code, suggest a single origin (unless of course there are functional differences among possible codes, which would make them non-arbitrary), while clearly adaptive similarities might arise through convergence (see whales and icthyosaurs). About this time we all realized we had other things we were supposed to be doing– meetings, lectures, etc. So we split up, and headed for our varied destinations. As we did, the first student said, “This is what college should be.”