Unperceived cause and effect in evolution and survival

From Evolution for Everyone by David Sloan Wilson, page 53-4. Looks at how the body has many hidden triggers of which we are completely unaware. You can do everything that makes objective and logical sense but may have missed the consequences of the pike in the pool (see below). The question is, how many human survival "war plans" are triggered by events that we fail to recognize? In the example below, a one minute exposure by a minnow to a pike after 262,800 minutes of life affects the remaining 1,314,000 minutes of life of that (average) minnow. That is incredible sensitivity.

It is as if at 12 years of age you were exposed (not injured or harmed by, just exposed) to something for 23 minutes which then materially modified your behavor for the rest of your life.

The idea of a new environment requires clarification. The wood frog (Rana sylvatica) lays its eggs in small pools of water during the spring. A given pool might or might not have predators. For a tadpole that hatches in a pool with predators, a pool without predators would be a new environment, but the population of tadpoles lives in both environments on a regular basis. What adaptations are likely to evolve in this situation? Ideally, a tadpole should be able to first assess its local environment and then display the appropriate adaptation. We have already seen an example of this kind of flexibility in male dung beetles, who assess their size and then display horns if they are sufficiently large.

I hope that you can see by now that a prediction such as this one is not destined to be correct. It is just a reasonable guess that requires work to confirm or reject. It turns out that many species are very good at assessing their environment and displaying the appropriate adaptations. Wood frogs have a plan A and a plan B for the presence and absence of predators, just as dung beetle males do for their own body size. The presence of predators is sensed chemically, and each plan involves a coordinated suite of behaviors (such as movement), traits (such as when to emerge from the pond). The environment has a huge effect on the organism, but not in the way that we usually associate with learning. Instead, a very specific feature of the environment (the presence or absence of a certain chemical) is used as a switch to activate genetically determined strategies.

As another example, imagine raising a certain species of minnow from the egg stage in a number of aquaria under carefully controlled conditions. When they are six months old, take a plastic model of a pike (a minnow predator) on the end of a stick and move it slowly through the water for one minute in half of the aquaria. Then do nothing for eighteen more months. That incredibly brief experience has a profound and lasting effect on minnow behavior, causing them to be wary of predators for the rest of their lives. This is not learning as we typically think of it. It is more like an elaborate war plan that is set in motion by a single phone call.

The only corresponding human example I can think of is the epigenetic impact of starvation in 1944 on pregnant Dutch women in World War II. As was to be expected, their own children born in the aftermath of the famine were smaller than normal. Unexepectedly, their grandchildren were as well, seemingly indicating some sort of biological survival game plan (when nutrition scarce, make smaller babies). I wonder how many other biologically determined alternate game plans are out there?

Now that I think about it, those minnows and pikes sure sound like the kids in the study referenced in this earlier posting Teacher Value Added and Student Outcomes in Adulthood