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What is Evolution?


In the last post, you learned that evolution is a theory, and that a theory is something that all the scientific evidence supports. But, what exactly IS evolution? Doesn’t mean we evolved from monkeys? No!

Evolution is very misunderstood. For example, some people think that we evolved from monkeys or chimpanzees, but we didn’t. We actually share a common ancestor with chimpanzees, which means we are distantly related to them, millions and millions of years ago, but we didn’t evolve from them. All life on this planet is related, and we are most related to other primates.

Evolution. Image of a chimpanzee sitting down on a small ledge.
We are most related to other primates.

So, what IS evolution? Evolution can simply be described as change over time. It is a fact that life on Earth has changed over time—we can observe that and verify that scientifically. For example, from studying fossils we know that there are organisms that were alive in the past, like dinosaurs and wooly mammoths, that are not here anymore. And we know that there are organisms alive today that did not exist millions of years ago. Life on Earth has changed over time.

We also know that organisms have changed over time as well— for example, horses in the past used to have 5 toes, and then they had 3 toes, and now today they only have 1. The horse has evolved, because it changed biologically over time. 

Evolution is change over time, specifically, a change in allele frequencies from one generation to the next. Evolution is all about alleles. 

So, what’s an allele? An allele is a version of a gene. For example, there is a gene for earwax, and there are two versions of that gene—one version creates wet earwax and one version creates dry earwax. These versions of the gene are called alleles. Wondering what a gene is? A gene is just a portion of DNA that does something. So, for example, there is a portion of your DNA that handles earwax, and that portion of DNA is called a gene. Evolution is just a change in the frequencies of alleles in a population, from one generation to the next.

Evolution. Image of 4 vials containing blood, and labeled A, B, AB, and O.
There are 4 types of blood in the ABO blood group.

Have you heard of ABO blood types? For example, my blood type is O+. You might know your own blood type. There are 4 blood types, called A, B, AB, and O. There is a gene for blood type, and the alleles are A, B, and O. 
Here’s an example of evolution using ABO blood types.

Say that you have a population of people. A population is a group of people who share a certain geographical area and find their mates within that group. So you have a population, and you test everyone to find out their ABO blood types. And, 50% of the people have A blood, 40% have B blood, and 10% have O blood. This means the frequency of A is 0.50, B is 0.40, and O is 0.10. 

Now, time goes on and people in the group mate with each other and have children. Then, we test everyone’s blood again and find that the frequency of A is now .30, B is .40, and O is .30. So, the amount of A has gone down, the amount of B has stayed the same, and the amount of O has gone up. There was a change in the allele frequencies from one generation to the next, so this is an example of evolution. 

Yep, that’s it! The allele frequencies changed from one generation to the next, so the population is said to have evolved. This is an example of microevolution, which is changes within a species from one generation to the next.

Macroevolution involves allele changes over thousands and millions of generations and can include the emergence of new species. Basically, a population can get separated from other populations, and then it accumulates so many genetic changes over hundreds or millions of generations that it is SO different from the other populations that it’s considered a new species.

Evolution. Two drawings of owls, one brown and one blue.
Organisms can change so much over time that they are considered to be a new species.

So, how exactly does evolution happen? What causes these allele frequencies to change over time? Well, there are 4 what we call, “forces of evolution:” natural selection, mutation, gene flow, and genetic drift. These forces of evolution change allele frequencies in different ways.

In summary, evolution is a change in allele frequencies over time. If you are looking at the changes in allele frequencies over short amounts of time, it is called microevolution. If you are looking at the changes over long periods of time, it’s called macroevolution.

Want to learn more about evolution?

Just take my Udemy course, “Exploring Genetics and Evolution Through Physical Anthropology: Anthropology 4U.”

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