Natural selection

Natural selection is now considered a theory, but it started as a hypothesis. And certainly it was very controversial. Remember, Darwin was far from the first scholar to embrace the idea of evolution (that the kinds of living things in the world had changed over time), but he presented a way that evolution could take place — and take place naturally, without any sort of plan. Some people were bothered by this — and some still are (usually for religious reasons, not scientific ones).

For this discussion I want you to take a look at those 5 steps of natural selection that I’ve laid out for you in the lecture (and on the slide from the lecture). Here they are below in slightly different form. Notice words like “chance” and “tend.” These are important, since natural selection is all about probability.

Individuals within a population are born with slightly different traits.
Some traits lead to a better chance at longer survival than other traits.
Individuals that survive longer will tend to reproduce more (have more offspring) than individuals that die sooner.
Parents tend to pass on their traits to their offspring.
If 1-4 are true, it must therefore be true that, as generations go by, traits that lead to better chance at survival will tend to become more common in the population, and therefore the population will change (evolve) toward having those traits.
So, let’s say you objected to this idea, and could not accept it. If you’re a scientist, you’d want to show that it is wrong. This would require you to “falsify” the hypothesis — which means prove that it is not true. So, you’d need to show that at least one of those five steps is simply wrong.

For this discussion, imagine that you’re a skeptical 19th-century scholar that doesn’t approve of Darwin’s idea and wants to put him in his place. Pick ONE of those five steps and tell me how you might try to prove that it isn’t true!

Sample Solution