Thursday, June 23, 2011

Day 23: Question Assumptions

The traditional evolutionary example is the story of the peppered moth. Here's how the original goes, as I have heard in numerous ecology and evolution courses and accepted as a really good example:

We are looking at England and we are looking at these small moths that are predated on by birds. So the story goes that before the industrial revolution in England the majority of peppered moths were this molted white variety with much less being the darker variety. As the theory goes, the lighter peppered moths could hide more easily on the light coloured lichen that covered the bark of the trees. When the factories began to open with the industrial revolution, the soot killed the lichen that covered the trees, making the trees appear darker. The theory goes that the moth population began to have more of the dark variety, which now had the advantage to blending into the tree trunks to hide. If the moth can hide, it won't get eaten and will have more offspring, passing that trait on to the next generation.

This is a great example of natural selection and is in every intro genetics, evolution, and ecology textbook that I can remember reading. It's simple. The conclusions are obvious. To pass on genes, you have to survive. To survive, you can't be eaten. To not be eaten, you can camouflage with your surroundings! Great!
An illustrated picture of peppered moths from

So what's the problem? There are assumptions that are questionable. The first is a misunderstanding of the behavioural ecology of the moths. It turns out that some studies showed that the moths are rarely found on tree trunks. The second is a human bias. Humans use sight as a primary sense, so the researchers immediately thought of camouflage, something that is important to us. Birds, the predators of these moths, can sense other spectrums of light, such as UV, in which both varieties of moths are equally detectable, so blending in for our visual spectrum is also meaningless. However, predation studies do seem to indicate that a predator can find and eat more of the darker form in unpolluted areas and more of the white form in the polluted areas. The scientific debate was raised by Jerry Coyne as he critically questioned the original Kettlewell experiments.

I'm not here to say who is right, since science is never decided that way, but is decided through exploration of the scientific questions. I'm just curious why these assumptions took 50 years to be truly questioned. There were studies in the mean time that explored the questions, but not in such a fundamental form. How much of science is based on a couple unknown assumptions? And how easily these assumptions can travel throughout a field as hundreds of papers begin to cite a big study that they build off of, and other papers cite those papers and so on and so on, except there may be a big glaring flaw in that original paper that no one sees, yet everyone builds on top of.

So how can we avoid this? I'm always told to question my assumptions, but it is much harder than it sounds, yet it seems so easy and obvious to question someone else's assumptions, to some extent. For example, in paleolimnology, we identify different species of algae or invertebrates in the sediment layers, sometimes thousands of years back. We know what the optima ranges are for various factors that allow them to survive in the present day, such as temperature, pH, salinity, etc., but how do we know that these are the same optima as that species had hundreds of years ago? I still don't understand this. But for something even closer to me, such as the experiment I designed in the kiddy pool, what am I missing? I know I'm missing something, but what is it? Now that I have some of the results back, I'm wondering if the nutrient availability in the water is temperature dependent, not necessarily even biological, but due to physical attributes of the nutrients, of the sediment? Not letting the system settle long enough to reestablish the algal population in the new containers? Why the spikes weren't noticed in the sampling right away - was it a sampling error, or does it take a while for the nutrients to diffuse in the water? And that's just a few things that I was able to notice, what haven't I noticed?

I know one way to solve the question assumptions problem is to tell other people about the idea and the project to get new perspectives. This also seems like such a simple, obvious step, yet I never really do it. I'm actually irrationally afraid that someone will find a flaw in my experiment that I didn't see, making my work completely useless and there goes my experiment. I know that from failure in science, you can always learn something, you can even learn a lot of really interesting things from failures. But... I don't want to fail! It's opening myself and my project up to criticisms that I'm afraid to take, but it's probably better to do so now than to finish the experiment and have so many bad assumptions that the results are truly meaningless.

I am in a good situation to have gone through the first stage of the experiment with the initial plan of using the first experiment as a trial for the second experiment, allowing me to change things as needed! Always prototype, that's another tenet of design, as is to get feedback from people with no detailed knowledge of the experiment/project. Writing up the methods to be critiqued by family and friends may be my task tomorrow, just to see what I've missed!

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