Evolution is a foundational principle within biology that forms the basis for many other theories. The theory of evolution was first described by Charles Darwin, a scientist who lived during the 19th century. Darwin’s theory proposed that all species on Earth have descended from a common ancestor and that new species arise through the process of natural selection. This theory has been supported by numerous scientific discoveries made over the years, and it is now widely accepted by the scientific community.
While traveling to the Galapagos islands near South America Darwin noticed that there were many different types of finches, each with a beak adapted to a specific diet. He postulated that the finches had all descended from a common ancestor, but over time they had evolved into different species in order to better exploit their environment. This was one of the first pieces of evidence Darwin used to support his theory of evolution.
Since Darwin’s time, much more evidence has been uncovered that seems to support the theory of evolution and that have refined Darwin’s original theory. Darwin believed that evolution was caused by something he called Survival of the fittest. Survival of the fittest means that organisms that are better adapted to their environment are more likely to survive and reproduce than those that are not as well adapted. Over time, this can lead to the emergence of new species.
Today we have much better technology than Darwin had access to. This technology has led scientists to further refine the theory of evolution. Using microscopes scientists have been able to show that all living things are made up of cells and that these cells have DNA in their nuclei.
This DNA is code that controls how a species grows and develops. Each time a cell divides, the DNA must be copied so that both cells can inherit a complete copy of the DNA code. Usually, this division occurs without incident. However, sometimes the code is copied incorrectly. When this happens, we call it a mutation, because the code has mutated.
Usually, mutations are harmless. However, sometimes they can be very bad, and can cause the living thing to die or become sickly. Occasionally a mutation might result in the living thing having an advantage. If it has an advantage then it is more likely to live to reproduce and to pass on that advantage to future generations.
Scientists believe that this is exactly what happened with polar bears. That believe that there was a mutation that resulted in white fur. That this white fur gave the polar bear an advantage in camouflage over brown bears. As a result, the polar bears were more likely to live and reproduce, and their offspring inherited the white fur gene.
Evidence for the theory of evolution includes vestigial organs. Vestigial organs are structures that have lost most or all of their original function, but they are still present in the organism. They are often very similar to functional organs in other organisms. One example is the human appendix. The appendix is a small pouch that hangs off the large intestine. It has no known function in humans, but it is very similar to the cecum, which is a pouch that hangs off the large intestine of animals such as rabbits and horses.
The cecum aids in the digestion of tough plant materials. It is thought that the human appendix may be a vestigial organ left over from our ancestors who ate mostly plants. As our diet has changed and we have started eating mostly meat, we no longer need the appendix, but it has not yet disappeared from our species.
Other examples of vestigial organs include the hind legs of some snakes, which are left over from their ancestors who had legs. These legs are non-functional and do not assist the snake in any way. Another example is the pelvis and leg bones of some whales, which are left over from their four-legged ancestors. These bones do not support the whale’s weight or assist in locomotion in any way.
However, there are counterarguments that creationists make that explain why living things would have these structures. One such argument is that a creator based the design of newer life forms on older life forms already created.
For a more detailed look at this viewpoint watch the accompanying video.
Punctuated equilibrium is the idea that most species remain unchanged for long periods of time, and then change very rapidly. This rapid change often happens when a new species emerges and quickly takes over the territory of an existing species.
The ability of a new species to quickly take over the territory of an existing species is called an adaptive radiation. When this happens, the new species rapidly diversifies into many different forms, each adapted to a specific niche in the environment.
One well-known example of punctuated equilibrium is the emergence of the mammalian class during the Mesozoic era, after the dinosaurs went extinct. mammals were small, rodent-like creatures before the dinosaurs went extinct. But after the dinosaurs were gone, they quickly diversified into many different forms, including apes, bats, lions, and hippopotamuses.
Punctuated equilibrium is thought to happen because most species are in a state of stasis (no change) for long periods of time.
During these periods of stasis, the species is well-adapted to its environment and does not need to change. However, occasionally something happens that causes a new species to emerge. When this happens, the new species quickly adapts to its new environment and rapidly takes over the territory of the existing species.
Punctuated equilibrium is a controversial idea, and there is still much debate among scientists about how common it is. Some scientists believe that it happens very frequently, while others believe that it is rare.
The main evidence for punctuated equilibrium is the fossil record. The fossil record shows long periods of stasis interrupted by brief periods of rapid change.
Critics of punctuated equilibrium argue that the fossil record is incomplete and does not provide enough evidence to support this idea. They also argue that the idea of punctuated equilibrium is too simplistic and does not take into account the complex interactions between different species in an ecosystem.
Divergent evolution is the process by which two or more species evolve from a common ancestor. This can happen when a new species emerges and quickly takes over the territory of an existing species.
It can also happen when a group of animals is isolated from the rest of its population and starts to evolve in a different direction. For example, this can happen when a group of animals is separated by a body of water or a mountain range.
Divergent evolution can also happen when two populations of the same species are living in different environments. For example, one population may live in a forest while the other lives in a Desert. Over time, the two populations will start to evolve differently to adapt to their different environments.
One well-known example of divergent evolution is the evolution of the finch species on the Galapagos Islands. These birds evolved from a common ancestor, but they now come in many different shapes and sizes, each adapted to a specific niche on the island.
Divergent evolution is thought to happen because the environment is constantly changing. This means that there is always a selective pressure for animals to evolve in order to survive.
Over time, these changes can add up and result in two or more species that are significantly different from each other.
Convergent Evolution is the process by which two or more species evolve from different ancestors but end up looking similar. This happens because they are both adapted to the same environment.
For example, many animals that live in cold climates have fur or feathers to keep them warm. This is an example of convergent evolution because these animals did not inherit their fur or feathers from a common ancestor.
Instead, they evolved these traits independently to adapt to the cold climate.
Another example of convergent evolution is the development of wings in birds and bats. These two groups of animals did not inherit their wings from a common ancestor. Instead, they both evolved wings independently to enable them to fly.
A Note From Mr. Bertoch About This Topic:
Evolution is a challenging topic to teach in any setting. This is even more true when the audience being targeted are homeschooled families. The dichotomy within the homeschool community around the topic of evolution and creationism is strong and fierce.
On the one hand, there is a group who strongly advocates that creationism be taught in science. I will call these individuals “creationists.” Please know that I do not do this in a derogatory manner.
On the other hand, there are evolutionists, who fiercely advocate that only evolution should be taught in a science class. Again, please do not think I am using the term evolutionist in a derogatory way.
When I wrote the HandsomeScienceTeacher courses, my original intent was to teach evolution and leave creationism out of it. Right up until the moment I recorded this video in fact. Throughout the past year, as I have worked on developing these courses, there has never really been any doubt in my mind that I was going to approach the topic of evolution from a strictly scientific standpoint.
Remember, however, that these videos are not scripted. It was perhaps five seconds before I hit the record button, that I mentally called an audible, and decided to instead take a different approach.
I decided that perhaps a better way to address evolution was to still teach it in its entirety so that I am true to the science. Which is my job as a science teacher. But, instead of insisting that the theory be accepted as absolute, I would instead use the tension between the two sides to create a unit around the importance of being objective.
The truth is, that on this issue both sides lack true objectivity. Both the evolutionists and the creationists tend to be less than willing to consider anything outside of their own views. Evolutionists state that evolution is an absolute fact. That it definitely happened. So strongly are they convinced of this that they typically cannot see their own lack of objectivity. This unwillingness to consider anything outside of evolution to explain the diversity of life on Earth is a problem that runs counter to how science is supposed to be done. They will insist they are objective, but when asked whether they would consider any other explanation for life, they state that there is no need to, because all the evidence points to evolution. Know that I am generalizing. Not all evolutionists are guilty of this lack of objectivity. But, many are.
Creationists are often guilty of this as well. Though I will say that I tend to see more open-mindedness among creationists than I do in circles of evolutionists. This is often because believing in creationism does not preclude someone from also believing in evolution. Many who believe in a creator also accept the theory of evolution.
The objectivity granted by those who do not need evolution to be true but who are willing to accept it, if evidence can be found to support it, tends to allow for a more honest examination of the evidence.
What matters isn’t that intelligent people agree with each other. What matters is only that they able to remain objective as they make up their mind. Which is how I attempt to teach this lesson.
By focusing on objectivity, my hope is that I can fully teach evolution, without insisting that it be accepted as absolutely factual. Students who complete this unit will walk away with a full understanding of the science behind evolution. However, they will be given the opportunity to use their own objectivity to draw conclusions about whether or not they believe the theory taught.
I think where I perhaps failed though, is that my own biases come out a little too strongly. I apologize for this. In attempting to show countervailing evidence, my own lack of belief in the theory of evolution I think comes through more strongly than I had intended.
My plea to the learner is that you ignore my bias. Your job is not to believe me. The views expressed are simply my opinions, where were shared in an effort to show that there are alternative views.
Your job is to learn about the theory of evolution. To attempt to remain objective. To examine all the evidence, and then to make up your own mind about it.
I respect anyone who disagrees with me. So long as you drew your conclusions objectively.
The Importance of Remaining Neutral
Scientists try to remain neutral when studying the Universe. They try to allow the data and evidence to lead them wherever it may. However, when it comes to the topic of evolution, they don’t always accomplish this goal. Many scientists refuse to believe or accept any evidence that might point away from evolution.
This strongly held position, that there is no creator, can cloud their judgment. It results in their immediately dismissing anything that might suggest a creator actually does exist.
The same can occur on the other side of the debate with creationists who may not believe in evolution and as a result may dismiss any evidence that it is occurring.
Check Your Own Biases
Are you allowing your strongly held biases to cloud your opinions on this topic? To an extent, we all likely do this. Consider the evidence both for and against evolution and then make your own informed decision.
This article talks about evolution, but it doesn’t go into near as much detail on the debate as the video does. Make sure to watch the video to really get a good sense for the evidence that is both in favor of evolution and also against evolution.