By late winter everything knows. Nettle shoots with new leaves so deeply dark they seem more black than green rise out of moist loam a long creek bottoms fertilized by black used-to-be green alder leaves and dead salmon. Newts with chocolate backs and bright orange bellies and rough rubbery skin clasp in a days-long embrace, swimming together in the quiet water of overfull ponds and sloughs and ditches and rain-filled ruts cut into muddy roads that should never have been built. Song sparrows belt out song sparrow song into a sunrise with no sun, a gray fish-belly band of wan light growing over the eastern ridge.
Humans know in that special, brainy, convoluted, gray matter way in which humans know things. Dr. Bill Bradshaw studies how plants and animals adapt to changes in day length, and he likes to project a graph of temperature plotted over a year of time, a jiggly line that eventually does indicate colder winters and warmer summers. There is a similar line for rainfall that lurches and climbs into wetter winters and then descends back to drier summers. But the line for daylight increases toward the summer solstice in a curve as dependably smooth as a piece of rounded river bottom basalt. Then Bill asks, “Which one would you bet your life on?” In other words, if you were a living thing going about the business of living in order to continue living and ensure that your genes stay alive in the next generation, would you wager that in late winter tomorrow will bring rain or that it will send along just slightly less than three additional minutes of daylight?
People do have circadian-clock genes with cryptic labels that sound like spy names: Per2, Per3, Clock, and AANA. These could influence our response to seasonal changes in day length. Human populations existing at different latitudes differ from one another in the prevalence of genetic variants for each of these genes, and it is tempting to speculate that natural selection has favored certain genetic variants that are better suited to environments with varying seasonality. But this story has a boring ending—most likely these changes in the frequency of our day-length genes came about because of chance rather than the imposition of natural selection in seasonal environments. This makes sense to me. I have a big woodpile and a full pantry and very little to lose if I bet in the wrong direction and don’t behave myself as the equinox approaches. I can screw up and plant my tomatoes and corn and squash into the cold wet ground right now, then after it all rots in a few months I can go to the garden store and buy more starts and seeds. It’s hard for me to imagine that at this juncture natural selection is the omnipotent master of my behavior.
Perhaps selection isn’t sifting human clock genes. But every other thing around us seems to know that something is up, even in late winter: camas and cattail shoots, chorus frogs, green hazel buds, garrulous towhees, growing garlic, a few early garter snakes, the first yellow wood violets, red-tailed hawks twirling together with legs outstretched, varied thrushes wheezing asthmatically, red fox with winter hair falling free. Despite our fluorescent lights and forced-air heat and clocks and watches and nine-to-five and everything running twenty-four-seven that has blotted out our intrinsic knowledge of the seasons, I believe that we still know in the way that plants and other animals know. We sense the quickening pace of morning, that precious extra hour of evening light. We send a glance toward spring and feel that fully–formed feeling, that deep round yes in our chest—we have made it through one more winter. Or maybe this is just a deep round sigh of relief as the day length slowly and predictably progresses back to something more akin to our equatorial roots?
Hard to say. Personally, part of me is already missing the quiet introspection of winter. I’m tearing around and tearing things up, re-landscaping my back yard and trying to figure out what needs to be planted when and where. I do this even though natural selection will no longer be beating me about the head and ears because my day-length genes aren’t just so. While there seems little reason to bet on anything anymore, my money will stay on the daylight. I knew it was coming.
This piece first appeared in Nature Trails, the monthly publication of the Eugene Natural History Society.
©Tom A. Titus