Evolution is widely regarded as the most important phenomenon in modern biological sciences. But it has a very contentious history in terms of how it's regarded by the general public, in particular with various religious groups. So what is it about evolution that makes it controversial?
Well, it's not the process of evolution itself, and it's not even the observable patterns that have arisen from that process. The process of evolution is factual. This is the second video in a two-part installment of EvoEd, and in part one I outlined this factual process of evolution.
In this video, we'll look at some of the patterns in nature that are a direct result of that evolutionary process. After that, we'll dip our toes into the creation versus evolution conversation, try to figure out what part of evolution really is objectionable to creationists, and why evolution has become an immovable sticking point for many. By way of a recap, the process of evolution can be broadly summarized as follows. DNA mutations that lead to new proteins, that lead to new cell functions, that lead to new traits or characteristics emerging that are selectively advantageous in populations or become more widespread due to things like founder effects and bottlenecks.
As this process occurs over and over and over, it results in speciation. Today what I'd like to do is to talk about just three of the different types of patterns that we can observe that are due to this process of evolution. These patterns are DNA similarities, homologous structures, and the fossil record. Number one, DNA similarities.
DNA codes for a type of molecule called RNA, and RNA is used to produce proteins. Proteins, also sometimes called enzymes, are the molecular machines that do almost everything that a cell needs to function. A mutation in DNA can change the way that a given protein functions.
And DNA mutations, they're actually kind of common. Sometimes mutations are induced by outside factors like solar or nuclear radiation, but most of the time, mutations just happen because the microcellular machinery that copies your DNA isn't perfect. I mean, the machinery is good.
It's really, really good. Our DNA copying machinery in our cells, essentially it's a set of enzymes, can copy DNA with an accuracy of about 99.999999% That's only about one mistake out of every 100 million base pairs of DNA that it copies. The kicker is this though. Humans have about 3.2 billion base pairs of nucleotides in their genome.
Some organisms have even more than that and others have less. But since our DNA copying machinery is only about 99.999999% accurate, that means that it would make about 30 mistakes or so every time our entire genome gets copied. Most of these mistakes are meaningless or occur in non-coding segments of DNA.
But some are in coding regions that produce proteins. If we start to analyze how similar the DNA is across various species, we can start to put together a pattern of relatedness. So let's say that we're looking at a group of different primate species.
Now, it's not practical to compare the entire genomes of these species. So instead, we'll pick a single gene to compare. In this case, we'll pick a gene called cytochrome b. The cytochrome b gene makes the cytochrome b enzyme and that enzyme is used in the mitochondria and helps to facilitate the production of an energy molecule called ATP. When we look at this sequence of this gene across this group of species, what we would find is that the cytochrome b sequences of the Langer and the Colibus are really, really similar.
as are the cytochrome b sequences for the baboon and the mangabe, and the sequences for the human and the chimpanzee. We can carry on from there. The rhesus monkeys sequence is most like the sequences that we find in the baboon and mangabe, and the sequence found in the mona is more similar to those three species than any other species in our group.
We could also plot out where the gorilla, the orangutan, and the gibbon should go in our diagram. purely based on how similar their cytochrome b sequence is to the other species in our analysis. We would also discover that the Langer and Calibis sequences, those are more similar to the sequences that we find in the baboon mangambi group as compared to the sequences that we find in the human chimpanzee group.
And so at the end of this whole process we have this tree-like structure. In a very technical sense all this tree is really telling us is how similar the cytochrome b gene sequence is across this group of species. But because we know that DNA has a natural rate of mutation This allows us to say, with a degree of certainty, that species with similar gene sequences share a recent common ancestor.
And it's the buildup of mutations in different populations of that ancestor species that has resulted in the two species that you see today. Number two, homologous features. Homologous features are structures in different organisms that have a shared ancestral origin.
One of the poster child examples of a homology is the limb structure in vertebrates. Whether we're looking at bats or dogs or humans or birds or whales or frogs, the bone sequence from the shoulder and beyond shares the same pattern. That pattern is one bone, two bones, many bones, and then long bones.
Now a dog's leg and a bird's wing may look pretty dissimilar, But they share this same basic structure being one bone, two bones, many bones, and then long bones. This pattern is incredibly consistent across vertebrates. The only real exceptions in vertebrates would be something like snakes or certain kinds of amphibians that don't have limbs. Since we know the process of evolution acts on vertebrates, and we know from genetic analysis that vertebrates share a common ancestor, then we can say that this limb structure was a feature of the common ancestor that these groups shared.
And it was a feature that was conserved over hundreds of millions of years. Other homologies include things like the way that bodies are segmented in arthropods. Arthropods being things like insects and mollusks or the basic leaf structure across different types of plants which at first glance can look quite different. Homologous features support the fact that groups of species share a common ancestor. Number three, the fossil record.
Okay, right off the top, what are fossils and how are they made? Well, there have been times on earth when something dies and gets buried rather rapidly, say by mud. It could be in a landslide, it could be on the land, it could be in the ocean.
A couple of things happen here. First, the fleshy parts of whatever died can rot away and decompose rather quickly. Leaving the bones behind or the shell bits or the exoskeleton or the wood depending on what died These harder materials are much slower to decompose but as they do little bit by little bit water seeps into the little spaces that are left behind and What gets left behind then are whatever minerals were in that water? So the bone very slowly gets replaced with minerals like iron and silica and calcite As this process occurs over the span of several thousand years, the bones of the animal or the parts of the plant become completely replaced by minerals and those minerals turn to stone, making perfect stone replicas of the remains of whatever died. This process occurs all over the world but you need the right kind of organism dying in the right kind of way and it has to happen in a layer of earth that we have access to or else we never find it.
Paleontology is an entire field of study. I can't even begin to touch the surface of it here. But there are a couple of notable things about the fossil record and evolution that I can point out.
First, the fossil record features lots of species that no longer exist. This would make sense if they lived a very, very, very long time ago and they either went extinct or they underwent significant changes and speciated into something new. Second, we find virtually no evidence of modern day organisms in ancient rock strata. If we take a look at the Ordovician era fossil sites, and there are an incredible number of these sites in southern Ohio and in northern Kentucky, the rocks at these sites are about 445 million years old.
At these sites you'll find all kinds of marine fossils. Things like brachiopods, crinoids, trilobites, cephalopods. Bryozoa, among other things. One thing that you'll never find in this fossil layer though, are Jod Fish.
I'm not just talking about modern day Jod fish, like a clownfish or a blue tang or a barracuda. I'm talking about any jawed fish at all. The first jawed fish in the fossil record don't appear until millions of years later in the Devonian time period.
And even then, the fossilized jawed fish specimens we find aren't from modern day species, they're from species that have long disappeared. Now you may have heard of something called living fossils. That's when the body structure of a modern day species, like the coelacanth, closely resembles the body structure of a species that we find in the fossil record from millions of years ago. But this is important, they're not actually the same species. They come from the same taxonomic group, and even though they look somewhat similar, they're nonetheless still significantly different.
As another example, you'll never find dinosaur fossils in the ancient rock from the Ordovician era either. Dinosaur fossils don't appear in the fossil record until nearly 200 million years later, starting in the Triassic period. Incidentally, we also never see trilobites in the fossil record after they abruptly disappear around 240 million years ago.
If trilobites lived in the same time as humans or even in the same era as the dinosaurs, we'd find them in more recent rock layers. These features of the fossil record make it completely consistent with what we might expect to find if the earth had a deep, deep evolutionary history. It's indisputable. It's literally written in stone.
So these things, the DNA similarities, the homologies, the fossil record, these are just three of the lines of evidence that demonstrate the result of the evolutionary process occurring over time and over space across planet earth. And there are lots of other patterns that are a result of the evolutionary process. Broad scale things like the geographic distribution of species and island biogeography or small scale things that occur on a species level like vestigial structures. Vestigial structures are features in organisms that seemingly have no use, like remnant eyes in blind cave fish, or the whale's pelvic bones, or even wisdom teeth in humans, some might argue. But here's a question.
What if we didn't have some of this evidence? What if the fossil record has significant gaps in it? What if we had no fossil record at all?
Or what if there wasn't this... broad sweeping pattern of homologous body parts across species? Or what if DNA sequences from one species to the next weren't that similar?
Remember, all of these things, these are patterns that are a result of the process of evolution occurring. The process itself is factual. The patterns, while cool, are different from the process. Even in instances where we can't detect a particular pattern Evolution is still occurring.
In order to explain this, let me take a bit of a detour. Consider this. Imagine a future where we colonize Mars.
And imagine that we take a few species from Earth along with us. Let's say we take palm trees, we take a species of swallowtail butterfly because they're gorgeous, we take the American goldfish, a spinous tristis, because it looks good. And it sounds good. These three species are not that related. There's a plant, an insect, and a bird.
Then imagine after we go to Mars that Earth gets destroyed by a passing comet. This is a tragedy of a story. But anyhow, over the first thousand years on Mars, the palm trees, the butterflies, the birds start to reproduce and spread out.
I mean, let's just assume that that's possible on Mars just for the purposes... of this detour. So these three species, they spread out and different populations start to form.
Right off the bat, there is no fossil record. And maybe fossils never form on Mars because of Mars'unique geology. But the processes of DNA mutations leading to new proteins, leading to new cell functions, leading to new traits or characteristics that are selectively advantageous in populations, that process, the process of evolution, is nonetheless occurring.
Evolution on Mars, in this example, is still a fact even though there's no fossil record. In addition, there are no homologous structures between these three groups. And when you compare the DNA of these three groups, well their DNA is more different than it is similar. So we've concocted a scenario where the factual process of evolution is occurring but there are no evolutionary patterns evident in nature.
So just because a pattern can't be seen doesn't mean that the process isn't real. Alright, let's get back on track. So how does all of this inform the creation and evolution conversation?
Well, first of all, Gaps in the patterns that emerge from the evolutionary process don't disprove the evolutionary process. Instead, those gaps just give us something fun to explore and to try to figure out. The second thing, and this is kind of mind-blowing to me, take a look at some real images that come from the major creation museum in Petersburg, Kentucky. These images are showing speciation over time. You see a single ancestor species of palm tree, a single ancestor species of swallowtail butterfly, and a single ancestor species of finch.
And over time the diagram is showing speciation occurring. How does the museum claim that these speciation events occur? Well, by genetic change that by definition leads to new cell function and new phenotypes which they point out can be selectively advantageous in populations.
So in a weird and crazy way... The Creation Museum actually depicts the process of evolution and actually articulates their version of how the process works. Though I will say that their understanding of DNA mutation is a little bit wacky, but we'll leave that part alone for now.
It would seem that their main issue isn't really with the process of evolution. Their main objection has to do with the age of the Earth, which they claim to be 6,000 years old. They point out that there's No way that evolution could produce the amazing diverse set of species that we have, originating from a common ancestor, over such a short period of time.
And I 100% agree with this. If the Earth is only 6,000 years old, as they contend, then yeah, maybe some version of their creation account is correct. And if it wasn't a deity who was responsible for the creation of species, then it would definitely have to be some kind of extraterrestrial force. that brought life here to Earth.
Because not a lot of speciation, in the grander scheme of things, can occur over such a short time period. So in a way, creationists might more accurately be described as young Earthers, because by and large they depict a process of speciation that's somewhat consistent with the process of evolution. I suspect that a big part of the stigma against evolution in America is because of its implications. If species arose purely through natural processes, instead of being breathed into existence by an all-powerful supernatural deity, then for some people it may call into question some of the tenets of their religion if their religion adheres to a supernatural creation narrative. And if a religion is wrong about something as fundamental as where do species come from, then there could be some concern that it might then also be wrong about other important things.
It would be simpler in those situations if species didn't arise through evolution, or even if humans didn't evolve. Then there would still be space to accommodate a simple and straightforward deity-based creation narrative. Unfortunately for evolution deniers, the process of evolution is a fact, and the patterns that have emerged from this process occurring over billions of years are literally everywhere. Thanks for tuning in.
I'll see you next time.