Principles of Evolution, Ecology and Behavior: Lecture 1 Transcript
January 12, 2009
Chapter 1. Introduction [00:00:00]
Professor Stephen Stearns: Biological evolution has two big ideas. One of them has to do with how the process occurs, and that’s called microevolution. It’s evolution going on right now. Evolution is going on in your body right now. You’ve got about 1013th bacteria in each gram of your feces, and they have enough mutations in them to cover the entire bacterial genome. Every time you flush the toilet, you flush an entire new set of information on bacterial genomes down the toilets. It’s going on all the time.
Now, the other major theme is macroevolution. This process of microevolution has created a history, and the history also constrains the process. The process has been going on for 3.8 billion years. It has created a history that had unique events in it, and things happened in that history that now constrain further microevolution going on today.
That’s one of the tricky things about evolution. It has many different scales. My wife always gets frustrated with me. She says, “Well when did that happen?” I say, “Oh not too long ago, only about 20 million years.” And, you know, that’s what happens when you become an evolutionary biologist, you zoom in and out of deep time a lot. And this process of microevolution is going to be the first thing we examine. It’s the nuts and bolts. It’s what’s really created the patterns. But the patterns of macroevolution are also very important because they record the history of life on the planet and they constrain the current process.
So the evolution part of the course is set up basically with two introductory lectures. Then I’m going to spend six lectures talking about microevolutionary principles. So these are things that you can always return to if you are puzzled about a problem. Then there’ll
be five lectures on how organisms are designed for reproductive success. This includes cool stuff like sexual selection, mate choice, that kind of stuff. I usually manage to give the sexual selection lecture just about on Valentine’s Day.
Then we’ll do macroevolutionary principles. This has to do both with speciation, how new species form, and with how biologists now analyze the tree of life to try to understand and infer the history of life on the planet. Then we’ll take a look at that history, looking at key events – and this includes both fossils and the diversity of organisms – and some abstract organizing principles about life. So all of those are part of how we can analyze the history of life on the planet.
And then, just before Spring Break, we will integrate micro and macroevolution. We’ll do it in two different ways. We’ll do it with co-evolution, where micro and macro come together, and we’ll also do it with evolutionary medicine, where both kinds of thinking are necessary really to understand disease and the design of the human body.
Chapter 2. History of Evolutionary Studies [00:03:22]
So where did this idea of evolution come from? Well, there are always ideas. You can go back to Aristotle and find elements of evolutionary thought in Aristotle. But really it’s a nineteenth century idea, and in order to see how it developed let’s go back to about 1790 or 1800; so at the end of the Century of the Enlightenment.
At that point, if you were to ask a well-educated person living in a Western culture how old the world is, they would say, “Oh thousands of years.” And if you were to ask them, “Well, where did all these species on the planet come from?