The State Superintendent for Public Instruction in Arizona is up for re-election soon, and that means updating state standards to support voters and lobbyists. In a recent draft of updated science standards, the word "evolution" was removed, as well as the big bang theory. Naturally, science teachers are pretty upset. As I read comments online from supporters that think evolution is a made up theory, it becomes clear that people simply don't understand the term. The first thing we need to clarify is the word theory. Out of the scientific context, the word theory might imply just a guess or an idea. In science, we don't use the word lightly. A theory is a highly tested explanation of a scientific phenomena. If something is just a guess or prediction, we call it a hypothesis. To become a a theory, a hypothesis must have mounds of evidence. Can a theory be proven wrong? Yes. But I'd love for you to find me scientific evidence that disproves the theory of evolution.
When you think of the term evolution, what comes to your mind? Is it the idea of monkeys turning into humans? If so, you need to erase that image. The term evolution means change in genes in a population over time. Based on this definition, I guarantee you've seen evolution occur in your life repeatedly. (I'll give you examples in a minute). To be completely transparent to all my readers out there: yes, I wholeheartedly believe in God. And yes, I support the theory of evolution. The two are not mutually exclusive. I don't like saying I "believe" in evolution, because I think the word believe implies faith. We don't have to have faith that evolution is occurring, because we can see it happening! Let's dive in.
Scientists break evolution into two categories: microevolution, and macroevolution. Since you probably know the prefix "micro" means small, microevolution refers to small changes in DNA in an organism's genome. These could be caused by a variety of reasons such as random mutations or selective breeding. If these changes are beneficial to the survival of a species, they will become more common. If they aren't beneficial, the organism likely dies and that variation disappears. Ready for a few examples?
1. The Flu Virus- Ever wonder why you get the flu even though you got the vaccine last year? It's because this year's flu is a different strain than last year's flu. As the flu virus makes copies of itself, mutations (changes in the DNA sequence) occur. These changes are often resistant to the vaccine, reproduce quickly, and spread to new victims. This leads to the evolution of new strains, which is likely the cause of next year's flu season. Did we see changes in genes in a population over time? Check.
2. The Rock Pocket Mouse- Let's look at an example from my native area- the Sonoran Desert. There is a species of mouse that typically has tan fur. This is great camouflage on the desert floor. Every once in a while, a random mutation (changes in a few amino acid sequences) causes the mouse to have black fur. Living in the desert with visual predators like owls and snakes, this is no bueno. These mice get eaten pretty quickly because that gene is not beneficial.
BUT.... in the Sonoran desert there are areas that are volcanic. In these volcanic areas, the ground is covered in black lava. Now who survives well? Obviously, the mouse with the black fur. Over many generations we see that there are almost no mice with tan fur living in the volcanic areas, only mice with black fur. Did changes in genes in a population over time occur? You bet. Mutations aren't necessarily always good or always bad- it depends on your environment. If you want to see more about this cute little mouse, watch the first 5 minutes of this video:
Other examples of microevolution explain the reason we have so many dog breeds (selective breeding) and why farmers only save seed from the best crops.
Macroevolution (big changes) refers to the formation of new species, which in biology we call speciation. This form of evolution takes much longer- generally tens of thousands of years. To be considered a species, you must be able to reproduce and produce viable offspring. So this means that dog breeds are the same species, because a Labrador and a German Shepard can breed and produce puppies which can also reproduce. But if you tried to breed a dog and a cat, it wouldn't happen. Different species.
Darwin first saw variations among related species when he visited the Galapagos Islands in 1835. Among Darwin's famous finches, he noticed that finches that had large beaks ate large seeds, and finches that had small beaks ate small seeds. But were they the same species? He wasn't sure at the time, but we now know based on DNA evidence that there are 13 different species of finches living on the islands. Darwin wondered if God made each species, or if one species flew over from the mainland and evolved out on the islands. Based on DNA evidence we can see that the birds living on the islands are more closely related to each other than any one is to a species on the mainland. This implies one species flew over and evolved from there. (This is the same as your DNA being more similar to your family members than other humans on Earth). Now, do we have to rule out the theory that God could have a hand in this process? Of course not. But we know new species form, regardless of who you believe their creator to be.
Below is one of my favorite videos to show my students on Darwin's finches. Peter and Rosemary Grant from Princeton University set out to test Darwin's theory of evolution among finches on the Galapagos Islands. Their results were pretty spectacular- they saw the birds evolve twice within a short period of time.
It is estimated that there are over 8 million species on Earth, and there are many not yet discovered. There are currently new species being created, and species going extinct. Ready for some food for thought? If you are a religious person, you are no doubt familiar with the story of Noah's ark. In the story, God tells Noah he is going to flood the Earth, so Noah builds a huge ark, takes his family and two animals of each kind (male and female), and they live on the ark for about a year while everything else on Earth got wiped out. Do you think it is possible Noah had 8 million species on the ark? Of course not. If that bible story is true, the plants and animals Noah saved had to have evolved into the millions of species we have today. There is not a ton of evidence proving that a world-wide flood occurred... but if you are a faith based person and believe God had his hand in a catastrophic flood, then why couldn't He have also had a hand in the evolution of new species following the flood?
Up to this point, I'm hoping that most of you are thinking "okay, that makes sense." Most people can see that changes in genes in populations occurs all the time. But once we get to human evolution people freak. The bible states that God created man in his own image. If this is true, then how can we have evolved from other hominid species that don't look like we do today? I'm not here to tell you what to think or believe (remember, I believe in God too). But I want to clear up a few misconceptions that I frequently hear.
Misconception #1: There is no evidence of human evolution.
There is quite a bit of evidence showing that hominids have evolved over time. By looking at the fossil record, we are able to date fossils back in time and look at their characteristics. Over 6,000 hominid fossils have been found and analyzed. By using these fossils we can figure out how old they are, what areas of earth they inhabited, if they walked upright, and their ability to live in different environments. We can also learn about their behaviors if the fossils are found with tools or other artifacts.
As a biologist, DNA is always strong evidence that we like to lean on. When you analyze DNA of primates, humans and chimpanzees share more DNA than chimpanzees share with apes or any other primates. This tells us that chimpanzees are our closest primate ancestor. To clarify: does this mean that chimpanzees turned into humans? No. It means that we share a common ancestor. It is estimated that we branched out from this common ancestor between 6 and 8 million years ago. A great visual timeline can be seen HERE.
Misconception #2: If evolution is still occurring, then why aren't humans still evolving?
We haven't seen macroevolution in humans in a long time, but we have definitely seen small changes in the human genome in recent times. Take lactose intolerance for example. In the majority of species, only babies drink milk, and after infancy the gene for producing lactase enzyme (which allows you to digest lactose) is turned off. Several thousand years ago, being able to drink milk as an adult without getting sick became an advantage (possibly because farming became more common). In our species, the majority of adults can drink milk with no problems.
The average human height has also increased over time. 10,000 years ago, the average human height for a European male was 5 feet 4 inches. Currently, that average has increased to 5 feet 9 inches. This could be from access to better nutrition, or simply because females select taller males.
Misconception #3: If apes evolved into humans, we should not have apes around today.
This is a misconception stemming from the idea that if one species evolves into a new species, than the former one should no longer exist. This is like saying "if dogs evolved from wolves, we should not have wolves around today." This is not how evolution works. When species evolve, they generally branch out into multiple species, not one species simply evolving into a new one (see image). So as our ape ancestors evolved, there are several lineages that resulted. A great visual of the hominid/ape family tree can be seen HERE.
(If you are a biology teacher and would like more homonid evolution teaching resources, check out this blog post).
I realize this can be a sensitive subject for many. I will always have faith in a higher power, but also will not let that faith discredit scientific discoveries. The more we discover, the more we figure out how the two can go hand in hand.