When I started teaching 7th grade science in my second teaching job, I was sure I wanted to do a bunch of plant labs. I had taken a Plant Physiology class in college, and the labs were so much more relaxed and pleasant than animal or microbe-based labs. You’d be dissecting cotyledons or whatever, chillin and talking, without the worry of contaminating your bacterial samples, which smelled awful anyways, or the knowledge that you were causing a crayfish great pain.
The 7th grade curriculum was big on experimental design and the effects of varying one variable on an outcome, so I wanted to find seeds that we could grow in great quantities and have the kids come up with questions (ie, what happens when you give it lemon juice rather than water, what happens if you add an extra heat lamp, etcetera.) The first week was a total bust; most of the heirloom seeds I’d bought at considerable cost (120 students adds up) from a hardware store hadn’t germinated, and those that had germinated were of so many different species and varieties that it was almost impossible to see how we could do any kind of consistent experiment.
Then I hit upon dried Goya Red Kidney Beans (I tried black beans and dried black-eyed-peas, but the Red Kidneys grew the best.) We put them in several hundred little peat pots on top of the radiator by the classroom window on Friday, and by Monday, the eastern exposure and the overactive radiator had made these guys not only germinate, but push their cotyledons and seed leaves six inches above the soil. The plants were holding up the weight of the clear plastic take-out container tops we’d put over the pots to keep in moisture and produce a greenhouse effect.
Pretty soon, we realized what should have been obvious to me– all of the beans were clones of one another. They sprouted on the same day, flowered on the same day, fruited and formed seed pods on the same day, and looked almost exactly identical except as the vagaries of the classroom environment, their placement in the plant container, and our experimental manipulations altered them. You really could see what more or less light, more or less moisture or heat or lemon juice, did to each of the plants, because they were so much the same to begin with.
* * *
A couple of years later, I was camping in Southern Utah when we walked into a field of alpine wildflowers that was growing riotously during the few months of warmth, seemingly dozens of different varieties, all being tended to by squadrons of bees and flies. It would be almost impossible to tell what environmental conditions were doing to any one flower, or even to a section of flowers as a group. After all, the growth course of wild, uncultivated plants is highly variable. Some plants will grow at a rapid rate at first, shooting above the plants around them and grabbing onto sunlight– and then stall out. Others will wait as seedlings for years before shooting up when an opportunity arises. Even within species and varieties, there is enormous variation in growth course and life history between and within populations.
Imagine you went from meadow to meadow, trying to figure out which was the “best” to grow a plant in. The place where the plants were already tallest might be the best– or maybe the plants just got a head start there. So instead you find their initial height and then measure their growth from day to day or month to month, and say that the places where they grew the fastest were the best. Maybe there are some recognizable varieties that are known to grow faster or slower, so you “control” for those differences by giving them a bonus or penalty onto their measured growth rate. You then call the adjusted growth rate the “value added” of the soil and meadow.
Would this make sense? Not really. Even within varieties of a wild plant there is going to be significant variation in the genetically determined life history and growth course. Moreover, the interaction between soil type, water level, temperature, and growth rate will vary significantly from plant to plant, as long as they aren’t all the same genetically.
Human intellectual development is much more like the organic growth of wild living things– in fact, it is a form of such growth, of course– than it is like the growth– natural or experimentally modified– of genetically identical Goya Red Kidney Beans.