Friday, March 27, 2009

Seeing the Trees...and the Forest: Evolution in Nature

Over the past month I've been spending one evening a week learning more about forest ecology here in the Northwest. I'm not going back to school - would that my health were good enough for that - or planning some new career, but I am becoming a forest steward in a terrific program sponsored by the Cooperative Extension of Washington State University in conjunction with the Department of Natural Resources. The course is designed to help independent owners of small forests develop short and long term plans for their land.

My partner and I own five acres of northwest coastal forest filled with conifers like Douglas Firs, Western Hemlocks and Western Pines and deciduous tress such as Red Alders. Our primary goal is to maintain a healthy, sustainable forest where we, and our friends and family - and those who come after us - can walk, listen and learn from nature.

Putting myself back into a classroom on the other side of the desk brought back memories of my own school days, of favorite professors and classes, and most especially of the nature hikes I used to go on with my closest graduate school friends and a very special mentor, Dr. Alice Brues. During my last few years as a graduate student in Boulder, Dr. Brues would invite us to drive her somewhere up into the foothills where she knew of trails, or lakes, or special forests. I don't recall ever having to be pursuaded (or have my arm twisted) to go along, or even to be the designated driver. As Alice clambered over the rocky hills, binoculars firmly in hands, we'd watch her, watching and calling to birds, admiring wildflowers, and identifying trees. I'd never before been in the presence of someone who knew so much about nature and talked about it with such passion and authority. It was possible to imagine Alice completely comfortable walking through the woods with Charles Darwin and the two of them having an animated conversation about birds and beetles, a scampering mammal or an outcropping of basalt.

Within the first few minutes of my forestry class I knew that I was home again, in the woods. Themes that I've heard all of my life as a physical anthropologist were applied to species of trees, mammals and invertebrates found in forest ecosystems. As one teacher reviewed some basic species of tree identification in northwest forests I heard a familiar admonitition, "Watch for variation, though, when you're beginning to learn to identify trees...Even in the same species you'll see variation in height or width or even in the dimensions of leaves."

I heard in my mind a well-known quotation - actually the title of an essay, by a famous geneticist, Theodosius G. Dobzhansky, "Nothing in biology makes sense except in light of evolution." I thought about my walks over the rolling pine-needle strewn trails of the forest surrounding our home. As I sit under on a stump under a new grove of Red Alder, I sometimes imagine the mighty glacier that helped form these rocks, soils and hills as it retreated. I think of what has become a truism in science that, indeed, nothing makes sense in biology except in light of evolution.

This evening at dusk I came within three feet of a woodpecker, as I strained to see her markings and the length of her beak to determine her species. Was I was looking at a large downy or small hairy woodpecker? Careful to move slowly, so as not to startle her, I was so close to her I could hear her beak each time she struck the suet and seed brick. Suddenly she flew away, leaving me behind to make up my mind about her identification as I paused to examine the hole she'd chisled into the seed brick. While it's true that evolution helps us make sense of what we see, what are the clues we focus on to gain insight about the evolutionary process? Those clues - the observations that we can make around us in our own backyards - and in the privacy of our own homes - revolve around this phenomenon: variation in populations. And that - particularly when it comes to our own species - is the domain of the physical anthropologist.

Over the next few blogs I'll be talking about the importance of variation in populations and the study of variation by anthropologists - and a few naturalists or so. For now, consider that physical anthropology is actually organised around the investigation of a central paradigm - that we humans are all the same, and that we humans are also all different. The exploration and interpretation of this paradigm is a central task of physical anthropologists, whether we are considering human beings in the present or our ancestors in the past. And it is essentially the same paradigm that naturalists apply when they endeavor to tell a female downy from a female hairy woodpecker or, to ask themselves, in turn, why does this variation among and between species exist in the first place. Variation is an exciting and sometimes controversial subject, but it's absolutely essential to evolutionary processes and therefore to our understanding of nature and of ourselves.

I look forward to picking up here next time. In the meantime, learn this name: Ernst Mayr. That's it for now. Class dismissed.

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