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Defining Evolution 18: Homologous Features

The video above will sum up the key points of this chapter- in this case, why similar features shared by species cannot be used as evidence of evolution The full chapter, which features Rent-A-Friend and his fellow Nacho-eating arm chair philosophers, can be read below. Enjoy! #JesusLovesYou

To read other parts of this series click here

I was walking through the snow saturated winds on my way to Danny’s Bar, Grill, and House of Rabblerousing, cursing the name of Al Gore and wanting to scream out loud, “WHERE IS MY GLOBAL WARMING!?!?” You see, it was April, a time when, traditionally, the sun comes out and flowers bloom and temperatures sore ABOVE FREEZING. Yet here I was, slogging my way through puddles of slush, and squinting into curtains of huge, fluffy white snow.

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I was last to arrive at our round table in the back near the dartboard, and my friends Carl, Tom, Bill, and Captain Blue Beard were already warming up with root beer and mozzarella sticks.

“Where is my global warming?!?!” I finally blurted out.

“It’s climate change now,” answered Bill.

“What? Since when?” I asked.

“Since a few years back,” Bill explained. “There was this huge, multinational meeting on global warming in Washington, and on the day of the meeting some of the attendees couldn’t make it due to snow.”

“I remember that,” said Blue Beard. “On the same day, there were snow fall in places what hadn’t seen snow in almost a century. I figure it’s a bad sign when you’re trying to get people to join the fight against global warming on a day with record snow.”

“I think they missed a prime opportunity,” suggested Tom. “If I were them, I would have declared our meeting a tremendous success. Only one meeting and we’ve beat back the heat until it snowed in the Amazon!”

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“Hey, that’s funny right there!” exclaimed Blue Beard, giving Tom’s root beet a celebratory dink with his own.

“All that to say, it’s climate change now,” said Bill. “Because once they started trying to blame snow on warming, they realized they needed some new terminology.”

“I guess I shouldn’t be surprised,” said Carl, scowling. “You bunch of nuts aren’t just Darwin Deniers, you’re climate deniers too! What next? Are you going to try to convince us that the world is flat?”

“Hey,” I said, grabbing a mozzarella stick and pointing it at Carl for emphasis, “I’ve been to Hickman Nebraska, and I can tell you- it IS flat.”

“Well now!” exclaimed Blue Beard. “Does this mean three months of arguing about climate change, or arguing about the shape of the globe?”

“I think it means six more weeks of winter,” I said, my socks still wet with snow.

“And the globe is a shape,” said Tom. “You can’t argue about the shape of a ball. The argument is IF the earth is a globe.”

“Well of course it’s a ruddy globe,” said Blue Beard. “Otherwise I’d have sailed off the edge of it by now. Been trying for years.”

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“And before we go off on another long discussion about science or religion or something,” suggested Tom, “I have a few more questions about this whole evolution business.”

“Well, certainly, Tom,” I said. “What’s on your mind?”

“I was visiting my folks this weekend, and I was looking through some of my things, and I found a book from college. A biology textbook. And while we’ve talked about a lot of the things which it covered in its chapters on evolution, there was something they described in some detail which we haven’t talked about yet; namely homologous features.”

“Ya can’t be serious,” exclaimed Blue Beard. “Your college book says that men wanting to marry other men is proof of evolution?” He scoffed and shook his head. In the silence that followed, he took note of our faces and said, “That’s not it then?”

“No,” replied Tom. “Homologous Features are similar structures which result from common ancestry.”

“Hang on,” said Carl, swiping through his personal computation device. “I have a quote about this subject in here. Listen:

‘If you look at a 1953 Corvette and compare it to the latest model, only the most general resemblances are evident, but if you compare a 1953 and a 1954 Corvette, side by side, then a 1954 and a 1955 model, and so on, the descent with modification is overwhelmingly obvious. This is what paleontologists do with fossils, and the evidence is so solid and comprehensive that it cannot be denied by reasonable people [emphasis in original].’1

Berra, T., Evolution and the Myth of Creationism, Stanford Univ. Press, p. 117, 1990.

“Oh,” said Blue Beard.

“Does that make sense?” asked Tom.

“Not a bit,” admitted Blue Beard.

“It’s like this,” Tom began. “As far as I can understand it from my book and what I recall from school, when we look at the anatomy and physiology of different plants and animals, we find things they have in common. For instance, the two bones that make up your forearm are called the radius and the ulna, and they allow your hand to rotate around the central axis of your arm like this.” Tom put his hand out and flipped it palm up, palm down, a few times to demonstrate.

“That’s a lot useful,” admitted Blue Beard.

“We have a radius and ulna in our forelimbs, but so do lots of other animals. Rodents, bats and birds in their wings, dogs, cats, and even whales in their flippers have a radius and ulna. The theory states,” Tom continued, “that we all share these features because we, meaning all birds and mammals, have descended from a common ancestor which also had that feature.”

“That does kind a make sense,” admitted Blue Beard.

“Finally!” exclaimed Carl. “One of you can see the logical interpretation of scientific observation! The only reason we would share these features with lesser animals is because we had some common ancestor with those features!”

“Or,” I interjected, happy again to burst Carl’s metaphorical balloon, “because we have a common designer who chose to reuse good pieces of design for achieving a desired result.”

“We’re talking about science here, not religion!” Carl retorted.

“No, you were talking about evolution,” I reminded him. “Which is every bit as religious but far less scientific than Biblical Christianity.”

“Hold on now boys,” said Bill. “Before we come out of our corners, swinging, we should make sure the rules are clear. Blue Beard, you get what the idea is now?”

“Yeah. Something in the distant past had a radius and ulna, and that thing was the great great great granddaddy of birds and whales and peoples. So all of us having these bones is a long standing family resemblance.” Blue Beard looked around at us. “Does I got it this time?”

“That’s what I understood,” said Tom. “Carl?”

“For once the pirate is talking sense,” said Carl. “So which would you like to disagree with this time,” he said to me, “observable scientific facts or logic?”

“I’d like to talk about Jackson Pollock,” I said.

“Pollock?” replied Blue Beard. “You mean the fish? Oh, wait, no. I’m thinking Haddock. What’s a Pollock?”

“Paul Jackson Pollock was a painter of sorts,” I said showing one of the images of Pollock’s work I had pulled up on my personal computation device. “He was primarily known for this style of work.”

“It looks like a giant plate of alien spaghetti,” said Blue Beard.

“It looks like he just threw paint at his canvas with no intent to represent a place or object,” added Tom.

“That’s about right,” I said. “But while the work at first seems somewhat random and accidental, you can get to know his style when you study his many works. In fact, one team of researchers studied Pollock’s work so much that they were able to build a robot that impersonated his style.”

“You know, I would love to discuss art history,” said Carl dryly, “but before we continue, I think you need to admit that Homologous Features are obvious evidence for Darwinian Evolution. Just admit that and we can go back to talking paint.”

“My dear Carl,” I said. “You didn’t think I had changed the subject, did you?” Carl’s face registered a slight worry and confusion, so I continued. “I’m making a point about finding similarities in different works. Just as Pollock’s work all show a similar style, many of God’s creations show a similar design. It’s the similarities which help us determine the identity of an artist.”

“You’re begging the question by assuming intelligent design,” scoffed Carl.

“And you’re begging the question by rejecting it,” I said. “Which of course means we are both coming to the evidence with an assumption. But my assumption that God is the creator doesn’t need this piece of evidence to prove it. I believe that God is the creator because He said He was. Then, when I see common design, it makes sense that common design comes from a common designer. However, you are using homologous features as evidence FOR evolution, when your ability to interpret them as homologous features requires you to believe in evolution before you examine the evidence. Once again you’re forced to use Evolution as evidence for evolution.”

“Hold on,” said Tom. “Why can’t the evidence just speak for itself? When we talk about homologous features, we’re just talking about features that different species have in common, aren’t we?”

“Not entirely,” I said. “What makes similar features Homologous Features, is that both species in question got that feature from a common ancestor with that feature.”

“Of course,” said Tom. “Where else would common features come from?”

“There is the concept of convergent evolution,” I answered. “Carl, tell Tom all about it.”

Carl had that look of distrust he has when I ask him to explain something, but he did as I asked anyway. “Convergent evolution,” he said, “is when two different species evolve a common feature due to environmental pressures that benefits their survival, when they do not share a common ancestor with that feature. They evolve to have a similar feature as opposed to gaining that similar feature from a common ancestor which already had it.”

“For example,” I said, “bats and dolphins have very similar radar, which I’ve heard even comes from similar genes. But no one believes that bats and dolphins have a common ancestor which had that radar or those genes. Thus, the radar in both of these species is an example of convergent evolution. Right Carl?”

“Yes,” said Carl looking even more concerned that I was saying something with which he agreed. “Yes, that’s right.”

“Which means that common feature shared by bats and dolphins is not a homologous feature. Right Carl?”

“Well, yes, by most definitions. I suppose.”

“And how do we know that bats and dolphins aren’t both descended from an ancestor with that radar system?” I asked.

“Because we know what the common ancestors of bats and dolphins are,” Carl replied. “And none of them have any radar. The radar comes later, and isn’t shared by any of the other species which also evolved from that common ancestor.”

“So to tell homologous features from convergent evolution,” I added, “we have to look at the evolutionary ancestry of the species in question.”

“Yes,” said Carl. “You’re finally starting to understand some real science!”

“But that means,” interjected Tom, “that homologous features can’t be used as evidence for evolution.”

“What? No, of course they can,” said Carl. “What do you mean, Tom?”

“According to you,” Tom continued, “we need evolutionary theory to even know if a feature is homologous or not. But if the evolutionary story has to be established before we can tell if similar features are even homologous, then we can’t say the existence of homologous features are evidence for evolution, can we?”

“What?” Carl stammered. “Of course we can! No, listen. We find similar features, like the radius and ulna in species which descended from an ancestor which had that feature. Thus, birds and bats and humans and whales must have had a common ancestor.”

“But how do you know that the radius and ulna aren’t examples of convergent evolution?” asked Tom.

“Because we know the common ancestor had that feature,” said Carl.

“Meaning we are using an established evolutionary tree to determine if the radius and ulna are in fact homologous features.”

Carl had the slightly pained look he gets when he seems to be thinking. “Well, sort of. I mean, yes. But homologous features are one of the pieces of evidence that we use to build those trees.”

“Are you dizzy yet?” I asked. “Common features are homologous if the Evolutionary tree says the common ancestor had that feature. Then we use the existence of those homologous features to say the tree is valid. Imagine we’re deliberating the guilt of a murder suspect.”

“What does this have to do with…?” began Carl.

“Just applying the same logic to the courtroom,” I replied. “At the scene of the murder, we have footprints. Does that prove the defendant to be guilty? Only if we know they are his footprints. What Darwin is saying is, “We know the defendant is guilty, so those MUST be his footprints.” But when asked how we know the defendant is guilty, Darwin points to the footprints and says, “We know he’s guilty because we found HIS footprints at the scene of the crime!”

“That’s not what it’s saying at all!” said Carl.

“Then what is it saying?” I asked

“Well,” Carl stammered, “just listen to the quote I read. I think it says it all!

“..if you compare a 1953 and a 1954 Corvette, side by side, then a 1954 and a 1955 model, and so on, the descent with modification is overwhelmingly obvious. This is what paleontologists do with fossils, and the evidence is so solid and comprehensive that it cannot be denied by reasonable people.”

“So you’re saying that a 1955 Corvette has four wheels because it is descended from a 1953 Corvette which already had that feature?” I asked.

“Yes. Well, no. It’s a metaphor! The point is you can put things in order according to their similar structures to see which came first!”

“It’s a metaphor?”

“Of course! Cars don’t reproduce.”

“So the similar features they have are the result of an intelligent guiding force making decisions for engineering and aesthetic purposes?”

“Yes, naturally.”

“So while the comparison of the Corvettes shows obvious design and intelligent guidance, a similar comparison of similar structures in living things doesn’t show design and intelligent guidance because…?”

“Because living things reproduce!” Carl exclaimed. “They don’t need any intelligent designer. They do these things naturally!”

“Carl,” I said, “if cars could make new cars without our help, and could repair themselves when damaged, and could go out and get their own fuel when their tanks were running low, would that prove they didn’t need a designer? Would that prove that they were made by accident with no intelligence?”

“You’re changing the subject!” Carl exclaimed in frustration.

“No, I’m pointing out the blunder of your quote. This guy uses intelligently designed machines to explain the process he uses to determine an evolutionary sequence from homologous features. He demonstrates that the same sequence can be assembled from similar features even when there was a designer. Thus, by your example and his, similar features can be obvious evidence of intelligent design by a common designer.”

“I think there is more to it than that,” interjected Bill. “Just in terms of anatomy and physiology. Why does every ground vehicle have wheels? Every car has four wheels, right? But is it because they descended gradually from a common bicycle?”

“No,” answered Tom. “It’s because the wheel is a tremendously efficient mechanism of ground movement, and four wheels is more stable than three.”

“Exactly!” said Bill. “All of these cars and trucks have a similar feature because they need to do the same thing! They need to drive, see? And not tip over when they turn. Now,” he said putting out his hand, palm down, “what do all of these animals need a radius and ulna for?” He flipped his hand palm up, and then palm down a few times.

“They need to be able to flip their forelimb along a central axis?” said Tom.

“There you go!” exclaimed Bill. “Hand, foot, wings, flippers, all need to do THIS.” He demonstrated a few more times, this time with both hands, looking like he was doing some cheap impression of a penguin. “It’s a smart design which works.”

“And that is the key to examining living things,” I said. “Nature has brilliant design at every level. But there are lots of different versions of similar things. For instance, our eyes are very different than the eyes of a squid.”

“Yeah,” scoffed Carl. “The squid eye is better. Human eyes are a stupid design.”

“Oh, is that so?” asked Bill. “As a humble medical doctor, I am interested in the details of this revelation.”

“The human eye is backwards,” said Carl. “The squid retina is unobstructed by anything, so it gathers light more efficiently. Ours is blocked by a network of blood vessels. If your God had designed us, I doubt he would have screwed up something that obvious, would he?”

“Well, funny thing about that, Carl,” said Bill. “But if our eyes were built like a squids, we’d go blind from exposure to direct sunlight.”


“Those blood vessels don’t block our view, they protect us from radiation which would destroy our photoreceptor cells,” Bill explained. “And their location allows those cells to receive oxygen very quickly and recover from use, otherwise we would literally not be able to see for more than a few seconds on a sunny day, and might take hours or days to recover if we recovered at all.”

“Plus,” said Blue Beard, “I think if you toss a squid up in tree, it won’t be able to see as well as we do. But those guys got perfect eyes for swimming the briny deep around the coral reef.”

“That almost rhymed,” I noted.

“Yeah,” said Blue Beard. “I’ll work on that one for next time. Maybe put it to music.”

“And the thing one notices in the human body,” said Bill, “as well as in any living thing, is that its design is perfect for what it needs to do, you see. A squid eye is perfect for being a squid, and our eyes are perfect for us. But there is this irreducible complexity to each design, so that, if you tried to gradually turn one into another, it stops being able to do its job maybe at all, you see. In fact, when some part of the human body changes shape, even a little, the part stops working as well.”

“Speaking of eyes,” I added, “this is why I have to wear glasses. My eyes are just a little bit the wrong shape, and that makes me near sighted.”

“Exactly!” replied Bill. “And the same is true of our knees, or blood vessels, or teeth, or anything else. Changing the shape of one of our parts in any significant way is like changing the shape of some part inside a clock.”

“Oh, please,” said Carl. “You’re not really going to use the old “Blind Watchmaker,” argument, are you? I think science has discredited that sufficiently.”

“First of all, Carl,” I replied, “it’s not the BLIND watchmaker. Evolution is claiming to be a blind, and mindless, and purposeless watchmaker. The argument is the argument for design. If a watch needs a designer, then why would living things, all of which are FAR more complex, NOT need a designer? What similar features show is a common problem being met by a common engineering solution.”

“And you simply stating out loud that ‘science has discredited’ something doesn’t make it so,” said Blue Beard. “Course, if you want to explain to us how science has proves that complex things don’t need to be designed by an intelligence, then by all means enlighten us.”

“Natural Selection,” began Carl.

“Doesn’t make anything new, let alone design anything,” said Blue Beard.

“Mutations…” Carl tried again.

“Are a corruption of existing information and have never been seen to add information, let alone design anything,” interrupted Blue Beard again.

“Look, Homologous Features…” Carl tried once more.

“Show a common designer using smart designs to give similar functions to different kinds of animals,” Bleu Beard added. “Good grief, Carl. We been over all of this! None of those mechanism of evolution makes new things! Besides which, I gotta ask, since you know cars need a designer, and we’ve acknowledged that living things are far more complex, being able to make new members of their kind and self repair and all, how complex does something need to get before it doesn’t need an intelligent designer for it?”

Carl did what Carl does best when faced with a question he doesn’t like, and that was to sink into stony silence. I took that as an opportunity to wrap up the topic as I could sense the arrival of our Nachos.

“So, Tom,” I said, “are you seeing how the existence of homologous features can’t be used to support Darwinian Evolution?”

“I think so,” he replied. “It seems that one must already accept not only evolution, but a certain order of evolutionary descent before it would be possible to call two similar structures Homologous in the first place. And considering how each of those structures fulfills an engineering challenge, it certainly doesn’t demand an evolutionary explanation. I can see why you would see design in them individually or collectively.”

“Just like the fossil record,” I said, “I find that Homologous Features require you to first accept the evolutionary story by faith, and then examine the evidence in the light of that faith before it can be seen as evidence for evolution. Once again, evolution is used as evidence for evolution. As for me, I’d prefer to take God at his word when He says he created everything. It certainly makes more probable sense to have a brilliant intelligent designer as the cause of brilliant design.”

But I could say no more about it, as Wendy had arrived with our beautifully designed mountain of nachos. While it could be said that this pile of Nachos was very similar in many ways to the Nachos that had come before, I knew that was no accident of nature. These Nachos were designed by a wise and benevolent kitchen staff that loves us, and shows their love with cheese and jalapeños. Love has many forms. May we always be thankful.

Happy Nachos! And thanks for letting me be your Rent-A-Friend.

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Written by Bryan Melugin

Bryan runs, teaches science and theatre, makes cartoons and puppets, and wants everyone to know and love Jesus.

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