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Intuitive Answers for Evolution SkepticsBy: Mike Gashler
Are you skeptical about the theory of evolution? Do you have unanswered questions? Good! Never believe something just because it's popular or a lot of people say you must. Never believe someone who won't give open and honest answers to all your questions. I commend your skepticism! Now, let's do something about those questions...
Evolution is not something that happens to individuals. Evolution is something that happens to populations.
It doesn't happen between birth and death. It happens over many many generations.
Evolution does not happen because someone decided what to do. It happens because diversity naturally occurs in large populations.
Whenever there is diversity, some individuals will be more effective, and some individuals will be less effective. Some differences are helpful. Some differences are not so helpful.
When you've got a population with some helpful differences and some unhelpful differences, the individuals with helpful differences tend to thrive a little bit more on average. It's not fair. It's just reality. And that means after many many generations, the unhelpful differences tend to diminish.
It is very common for children to differ from their parents. Sometimes, DNA doesn't replicate perfectly. The errors cause differences. Sometimes, exposure to radiation can cause DNA to change. These are called mutations.
And sex even creates diversity on purpose! It combines the genetic information from two different creatures to produce a child that differs from both the mother and the father.
Long ago, creatures only reproduced asexually. Back then, evolution happened slowly because there wasn't as much diversity.
Sex creates more diversity. So populations that have sex evolved faster. In a sense, it can be thought of as a solution to not having enough natural mutations.
When exactly does a boy become a man? Nature operates with very small gradual changes, then humans assign boundaries and classifications. So if you want to understand this, it is necessary to put your categories on hold and think about processes.
In the process of asexual reproduction, one creature becomes two. In the process of sexual reproduction, two creatures become three. From that perspective, they are actually pretty similar processes. The biggest difference is that in asexual reproduction, the parent must produce 2 times the resources necessary for life. In sexual reproduction, each parent must only produce 1.5 times the resources necessary for life. So there is a benefit to having two parents help each other with the process.
We don't know exactly which cells first started working together to reproduce. Cells don't leave a lot of fossils for us to analyze. But all the life we find that appears to have lived during the first 3 billion years of the Earth's history only did asexual reproduction. And only life that appears to have lived during the most recent 1.2 billion years does sexual reproduction.
But we do know that it didn't start with two distinct sexes. As a silly demonstration, try clasping your two hands together. Then slowly pull them apart. When exactly did your two hands become separate from each other? It's like that.
Ha ha. The egg. Fish lay eggs. Fish have been around for over 500 million years. Chickens have only been around for a little over 200 million years. But that's just being silly. Let's ask a more serious question: Which came first, the heart or the veins that carry blood? Either would be useless without the other!
The answer is that neither existed as a distinct entity with its modern function before the other. Both are the product of a gradual adaptive process that spanned many generations. The primitive predecessors of hearts and veins were very different than they are now. They did not even start evolving to depend on each other until after they started working together, and they didn't originally start working together the way they do now.
As a more familiar analogy we might ask, which came first, cars or drivers or roads or gas stations? Well, cars were once carriages pulled by horses. When steam engines first replaced the horses, there were only horse drivers and certainly no gas stations. Slowly, cars and drivers adapted to each other. Now, bitumen roads and gas stations are adapted to facilitate modern driving habits. It's like that. Functions and purposes slowly shift, and gradually, various components become inter-dependent.
Nothing extraordinary ever happened by random chance. The odds of that happening are overwhelmingly small. If something is extraordinary, it was probably either created or it evolved.
Was your last roll just random chance? Yep.
Was random chance the reason you ended up with a seven? Of course not! That was persistence, not random chance.
Evolution is like that. It keeps "rolling" until it gets something that works. Evolution is a persistent process. Random chance is what it overcomes with persistence.
(9) How can a persistent process overcome the impossible odds of producing something as complex as human DNA?
There are four types of nucleotides in human DNA. And there are about 3 billion of them. So the odds of spontaneously forming human DNA have been compared to rolling 3 billion four-sided dice. That makes 43000000000 possibilities! What are the chances of finding a valid pattern among so many?
Effectively impossible! But that's not how humans are born. We don't emerge directly from primordial soup. We emerge from our mother's wombs. Evolution isn't something that happens to individuals. It happens over many generations.
When mutations occur, they usually affect only a few nucleotides in the DNA. So it's not like rolling all the dice together. It's more like rolling just one or two of the dice. A whole life is lived after each tiny adjustment is made.
There is just a tiny bit more probability that creatures with bad mutations will die before they reproduce. And there is a tiny bit more probability that creatures with good mutations will reproduce before they die. That tiny difference in probability is the only difference.
It is usually not a big enough difference for an individual creature to even notice! It is just enough of a difference that the population as a whole tends to slowly drift toward having creatures with more effective genes. This effect is called "natural selection".
Evolution does not say anything about whether or not there is a God. It only suggests that populations changed slowly over time.
Some people think evolution by natural selection is sufficient to explain the diversity of life without God. But even if they are right, that doesn't mean there is no God. It just means some other reason (besides the existence of life) is needed to serve as a basis for belief in God.
Many people with faith in God also believe in evolution. And many people who believe in evolution also believe in God.
Okay. There is still evidence that life evolved. You don't have to consider the evidence. And people who care about evidence don't have to consider your faith. I'm not telling you what to believe. I'm only telling you what the evidence says. Whether or not you care is your choice.
Certainty doesn't matter. Many people are certain about all sorts of false things. For example, some people are certain the Earth is flat. Yet there is plenty of strong evidence that the Earth is approximately round. It is much more telling that the evidence for a flat Earth is so flimsy.
It is easy to put faith in something that is not true. It is a little bit harder to find evidence for something that is not true. And it is really hard to find a lot of evidence that withstands the scrutiny of skeptical individuals for something that is not true. So finding a lot of evidence that withstands scrutiny is a pretty good way to tell what is true. (And it is much better than measuring the certainty of people.)
Even people who do not believe in evolution can still search for evidence. It doesn't matter what the scientist who finds the evidence believes. What matters is the story the evidence tells.
Yeah. That's pretty lame, isn't it?
Disparaging Charles Darwin doesn't hurt the theory of evolution. Charles Darwin didn't even invent the theory of evolution. His contribution was describing the role of natural selection in the process of evolution. But his opinions are now completely irrelevant. So much supporting evidence has been found since his death that only historians still care what he thought.
Unfortunately, there are a lot of creationists who still imagine scientists follow Charles Darwin. So given their motivation to disparage him, I think it is somewhat more likely that disparaging rumors about him are not actually grounded in evidence. But if it turns out that he really was a bad man, that really doesn't affect the theory of evolution.
No. Many forces can cause evolution to occur. Humans are another cause of evolution. Here are a few examples of evolution caused by humans:
(18) Okay, I understand how humans can promote evolution. Humans are intelligent. But how can mindless natural selection do it?
Consider what humans did to help their animals evolve. When winter came, the humans needed something to eat. Should they slaughter their best milk cow or the one that produced little milk? Should they slaughter their the sheep that produced the most wool or the one that produced little? Obviously, most people would choose to eat the animals that had the least value to them.
It didn't take a whole lot of intelligence to help animals evolve. The humans who did it did not have degrees in genetic engineering. In fact, genetics had not even been discovered yet. It just happened over a long time because people used a tiny bit of intelligence to influence each generation.
That's pretty-much how nature does it too. Nature is more hostile to creatures that are bad at surviving. So over many generations, creatures get pretty good at surviving. It doesn't take deep contemplation, just a small influence in a steady direction. In nature, that steady direction is survival.
Every time we find another piece of evidence, the gaps get a little smaller, but there are two gaps where there used to be only one! The number of gaps is steadily increasing!
Every piece of evidence is surrounded by a gap! What matters is not how many gaps there are, but how big the gaps are. And these days, the gaps in the evidence for evolution are getting pretty small.
Yes, there are some gaps that are bigger than we would like. But "bigger than we would like" is highly subjective. There really are no gaps big enough to accommodate any theories that suggest evolution never occurred.
Consider what science tells us about the shape of the Earth. First they told us it was round. Then they told us it was an oblate spheroid. Then they produced topographical relief maps of the mountains. Then they mapped the bottom of the ocean too. Then the maps were redone with finer granularity.
Our knowledge of the shape of the Earth has steadily been getting more and more precise. So, since our knowledge about the shape of the Earth keeps changing, does that mean it might actually turn out to be flat? No. Becoming more precise does not mean you were wrong before. It just means your new knowledge is better.
Our knowledge about evolution is like that. It is much more precise now than it was when a hundred years ago. It will keep getting more and more precise as time goes on. Does that mean it might be totally wrong? No. We're waaaay past that point already.
No. Theories are explanations that are not yet as precise as we want them to be.
In the picture above, the blue dots represent reality, and the red circles represent explanations. Evolution is a validated theory. (See the circle in the top-right corner). That means it is known to accurately describe reality, but it is not yet as precise as we would like. The circle will get smaller as more details are discovered.
We don't know everything. There are still many hypotheses that are compatible with the theory of evolution. But we know reality falls within the vague description provided by the theory of evolution.
I don't know. That's still an open question.
One of the most prevalent hypotheses is called abiogenesis. It suggests that the first life evolved from something called "proto-life" that occurred spontaneously in nature. Proto-life is something much too simple to be called "alive", but it is capable of reproducing and evolving. Although we know evolution occurs, we do not yet know if abiogenesis is how it got started.
Another hypothesis is called panspermia. It suggests that life on this planet somehow traveled through space to arrive on Earth. Another hypothesis is that some god created the first living cell and placed it on the Earth. Many believers hypothesize that the creation stories taught by their religions are metaphorical descriptions of how God supervised the evolution of life on Earth.
(24) I heard mathematicians computed the odds of abiogenesis occurring at 1 in 10000000000000000000000000000000.
What those mathematicians did was consider the simplest protein that occurs in a modern living cell, then compute the odds of that protein spontaneously forming assuming that a bunch of amino acids all came together with a random uniform distribution. They're actually right that the odds of something very complex spontaneously forming are absurdly small.
But that's not what the hypothesis of abiogenesis suggests may have occurred.
The hypothesis of abiogenesis suggests that the first proto-life was much simpler than anything alive today. The hypothesis of abiogenesis suggests that anything complex must have evolved. To back up this statement, let me quote from the second sentence of the Wikipedia article on abiogenesis. (Please feel free to look it up yourself to verify that I'm not just making this up.)
Modern cells do a lot of complex things in the process of reproduction. But if abiogenesis occurred, then all that complexity evolved later.
Let's consider an example of something very simple that can reproduce: Take a match. Light it. Toss it into a dry field of tall grass.
But I am suggesting that the first proto-life may have been a very simple chemical reaction. Fire is just a simple chemical reaction that a lot of people are already familiar with. As an exercise, let's consider some of the properties that fire has in common with life:
Is fire alive? No! (Well, sort of. Life is more of a spectrum than a binary concept.) The point is that a lot of complexity is not really necessary for something that may have later evolved into something complex enough to meet a modern definition of life.
Assuming something was as complex as possible is what people do when they want to conclude that it was impossible. If you don't want to give abiogenesis a chance, I'm not trying to make you. But if you do want to give it fair consideration, it's best to separate as much complexity from it as possible.
If abiogenesis really occurred, complexities like cell walls and proteins could have evolved later. Whatever first occurred spontaneously was certainly much too simple to be called "alive". So don't look for all the requirements of "life". Just look for the minimal requirements for evolution.
The only things needed for evolution are reproduction and diversity. Even simple chemical reactions can meet those two requirements to some extent. And simple chemical reactions occur spontaneously all the time! And when the Earth was very young, they probably occurred spontaneously much more frequently than they do now, because back then a lot of volatile chemicals had not yet reacted to neutralize each other.
I don't know. That's still an open question. Maybe they didn't evolve at all. Maybe something else happened. Let's keep all plausible hypotheses on the table of consideration until we know the answer for sure.
That's true. That's why abiogenesis is still a hypothesis. It might not even turn out to be true. Let's not pretend we know the answers before we can produce confirming evidence.
It's certainly easy to over-estimate how much scientists really know. After all, they seem to know an awful lot! But scientists are not gods.
The simplest organisms are very tiny and hard to study. And we've really only had the technology to study them thoroughly for a few decades. Most of the evidence we have comes from the chemicals we find in living cells, and we're trying to piece together what happened over the course of four billion years! That's a tough job, especially since there are so very many possibilities!
There is no question about whether evolution occurs in large creatures. We know it does. But how it happened billions of years ago in single-celled organisms is hard to nail down.
Fortunately, evolution does not depend on the knowledge of scientists to find effective evolutionary pathways. There are now an estimated 5,000,000,000,000,000,000,000,000,000,000 bacteria cells on the Earth. That number was once much smaller, but it has outnumbered the scientists as long as there have been scientists. Each of those living cells can be thought of as one of nature's simultaneous searches for another evolutionary pathway. Even if nature is searching in an unintelligent manner by slowly rolling the metaphorical dice of infrequent random mutations, it is still generally going to be more effective than intelligent scientists at finding effective pathways, because nature has much bigger populations.
"Ape" is just a grouping biologists use. This grouping includes humans, gorillas, and chimpanzees. But being grouped with gorillas and chimpanzees does not make you a gorilla or a chimpanzee.
Mammal is another grouping that includes humans. But being a mammal doesn't make you a whale. And rejecting evolution will not change how biologists group things. If it bothers you, too bad. Deal with it.
Nope. Dark skin is caused by a pigment called melanin. People with light skin just have less melanin.
One hypothesis suggests that light-skinned people lost their melanin by inter-breeding with the neanderthals who lived in Europe. If that is true, then dark-skinned people may actually have the stronger claim to representing the human species.
Yep. Other dating techniques must be used for older stuff.
As one example, uranium-lead dating is accurate over billions of years. Since uranium-235 and uranium-238 have different half-lives, a single sample provides two different clocks that can be used to cross-check each other. And with modern mass spectrometers, very accurate dating can be done with even extremely tiny samples.
It is common to be skeptical about dating methods, so many different dating methods have been developed and used to check each other. The Wikipedia article on chronological dating lists more than 24 different dating methods, and the all tell compatible stories. It would be pretty tough to imagine all of these methods being wrong in the same way. For example, if radiometric dating didn't work as it claims, it probably wouldn't agree with counting tree rings, or the growth rate of stalactites, or of well-studied crystals, or the many other techniques that also give similar results.
(34) Layers of strata were formed by Mt. St. Helens in a just few days! And modern tools have been found buried in layers of strata.
Yep, those things all happened.
Unfortunately, some people try to point at this event as evidence that layers of sedimentary rock also may have formed quickly. That would be true if volcanoes were responsible for types of rock. But they are not. A geologist who could not differentiate between sedimentary and igneous rocks would not be a geologist at all, and would have no business making claims about the ages of things.
Perhaps most importantly, these arguments only attack one method for dating things. In the early 1900's, that might have been devastating since not many dating methods had yet been developed. But these days, it's a pretty flimsy argument when strata layers are just one source of hints about the ages of things. If something cannot be demonstrated multiple ways, it should not be considered reliable knowledge.
To test a scientific theory, we use that theory to make predictions, then we wait to see if those prediction turns out to be right. When the theory of evolution was young, the physical appearance of living creatures and fossils were all we had to validate the theory. But if the theory was right, then what would that imply? What we expect to discover later?
It would imply that there were probably more fossils in the ground that told the same story about how things evolved. Were there? Yep!
It would imply that other extinct species related to humans might be eventually found. Did that happen? It sure did!
And it would imply that after we learned how to sequence genomes we would then find further evidence connecting ancestral lines together. Aaaaand ...? You betcha! Genetics did a lot more than merely confirm the things that had been theorized about evolution. It became the new most powerful tool we have for studying evolution. There is so much information embedded in DNA that we can confirm genetic relationships with extremely precise levels of statistical certainty! A whole new branch of science called phylogenetics emerged just based on studying relationships indicated in genomes, and many new discoveries about evolution were made because of genetics.
So yes, the theory as a whole is testable. And various specific aspects of the theory are testable too. Evidence that agrees with all aspects of the theory of evolution is discovered again and again. Every new fossil we find is a successful test of of theory, and more tests will be passed as time proceeds.
Here is an example experiment that can be performed again and again in a laboratory:
Just because evolution has not been successfully falsified does not mean it isn't subject to falsification attempts. If evolution had been a false theory, genetics would not have confirmed it. And if evolution had been a false theory, some flaw in the theory would likely be found. That hasn't happened. And if evolution was a false theory, presumably evidence would be found for something else.
For a while, some people thought evolution was falsified by the seemingly perfect roundness of the eyeball. For a while, some people thought evolution was falsified by the conundrum of which sex evolved first. For a while, some people thought evolution was falsified by the conundrum of whether the heart or veins evolved first. For a while, some people thought evolution was falsified by various other types of complexity that were deemed irreducible. Any of these challenges could have been real problems for the theory. But then the answer keeps being discovered. Again and again, we keep finding that evolution is better at refining complex things than even intelligent designers.
(39) Wait! Did you just say evolution is better at refining complex things than intelligent designers?
When human engineers have a few variables to optimize, they may do it using their own intelligence. But when human engineers need to optimize thousands of variables simultaneously that all interact with each other, they use genetic algorithms. A genetic algorithm is a simulation of evolution. It is much more effective at simultaneously tuning large numbers of things than human intelligence.
As an example, the electronic components in integrated circuits in the electronic device you are using right now were placed by a genetic algorithm. Humans don't do that task manually any more. It's too hard. There are too many variables. It's a job much better suited for evolution.
Designers tend to keep things as simple as possible. Great complexity is a sign that something is more likely the product of evolution.
Yep! Evolution can be a powerful tool.
If you wanted to cut your lawn, you would not use your teeth. You would use a law mower. If there is a God, surely he would be intelligent enough to use appropriate tools to accomplish his jobs too. Evolution would be a very effective tool to use for creating life. By contrast, trying to engineer it all manually might be an impressive feat, but approaching it that way does not seem very intelligent at all!
Also let's be careful not to confuse an analogy with evidence. Not everything that makes sense in our heads is actually found in reality. There is a lot of evidence that evolution is driven primarily by natural selection. But verifiable evidence confirming exactly where or if God fits into that process has not yet been found.
Perhaps. Very often, however, the opposite actually seems to be true.
In my artificial intelligence class, I give a certain assignment in which students are required to implement a genetic algorithm to train the weights of an artificial neural network to play a simple video game. Genetic algorithms are very simple to get working, but they can do things that are very complex. Many hundreds of students have successfully completed this assignment.
Every semester, I challenge my students to try solving the same problem manually, using their own intelligence. No one has ever successfully found a solution that way. This problem is just not suitable for being solved with intelligence. Tasks that require refining a lot of complexity simultaneously are much better-suited for the kind of persistent searching that evolution does.
(42) If life evolved, wouldn't we expect to see a uniform distribution of fossils for intermediate species?
No. Evolution does not advance in a steady linear manner. It advances in spurts and jumps.
Here is a plot of fitness over generations with a genetic algorithm. This simulation involved four populations separated on different islands or continents. The maximum fitness in each population is plotted.
Note how the fitness does not increase in a straight line. Biological evolution is like this. It occurs sporadically, rather than steadily. During periods when the fitness is flat (horizontal) for a while, many fossils with similar properties would be produced. Fossils for intermediate species are relatively rare because they must occur during the improving (more vertical) spurts of progress.
And it turns out that fossils are actually somewhat rare. Most things that die either decompose or are eaten by something else. Very specific and unusual conditions are necessary to create a fossil. For example, to become a fossil, a creature must die by falling into a tar-pit, or be entirely encased in amber, or somehow get quickly covered with dirt. The only reason we have as many samples as we actually have is because life has been happening on the Earth for a very long time.
Micro-evolution and macro-evolution are terms that were invented to describe how some people wanted evolution to work. They wanted to discover that life was like a playground swing, often rocking back and forth, but never drifting away from the place where its poles are firmly cemented into the ground.
Unfortunately, not all hypotheses turn out to be accurate. You can believe something just because it sounds nice, but that does not make it true. There is nothing like poles cemented into the ground to prevent adaptations from accumulating to cross specie boundaries.
The boundaries between species are human-made. There is no force causing nature to respect them. Nature is not even aware of them.
Ring species prove that can and do cross specie boundaries.
As a simple example, dogs can mate with wolves, and wolves can mate with foxes. But dogs cannot produce viable offspring by mating with foxes.
Many other examples like this exist. They show that small adaptations often accumulate to drift across the boundaries of what makes a species.
Humans are still evolving.
Evolution takes many generations, and humans have a poor ability to comprehend large time-scales. But your inability to see it does not stop it from happening. That's rather like watching a tree for ten minutes and saying, "It looks like it stopped growing".
I've often thought someone should start a population of penguins on the North Pole, just because we could. Why has no one tried this yet? I don't know.
Maybe no one sees any value in doing it? Maybe it would be more expensive than I realize? Maybe there are subtle ecological differences that would render it unsustainable? Maybe it actually has been attempted, but it didn't work out? Maybe it will happen some day.
It's probably like that.
Yes, DNA is coded information. No, coded information does not imply an intelligent designer.
Of course we have examples of coded information coming from intelligent designers. But that does not imply all coded information comes from intelligent designers.
The organized layout of molecules in a snowflake is coded information. In a coded manner, it describes the atmospheric conditions the flake passed through as it accumulated the nano-scale particles. Stripes of particles with magnetic polarity on the seafloor of the Atlantic ocean are coded information. They tell a story of how the magnetic polarity of Earth has changed several times while the continents slowly separated due to magma convection beneath. The eroded shapes of mountains encode the story of millions of years of the water cycle.
In a way, all evidence is a form of coded information. So any evidence of a natural process is code that was created by the natural process. Evolution just happens to be one of many natural processes.
Here are a few other well-known natural processes:
The Second Law of Thermodynamics says that entropy increases monotonically in closed systems. But all living things exchange entropy with their environments, and are therefore not closed systems.
Life is not anything like a cosmic accident. It evolved very slowly and very deliberately. Our present form is the accumulated sum of far more deliberate honing than it would be if we had been intelligently designed. The deliberateness is just spread across billions of independent events that shaped us for a multiplicity of purposes.
As a thought experiment, hypothetically suppose you had been created by an intelligent designer with an evil agenda. Perhaps, will of this evil creator was for you to spend your life harming puppies and breaking the knee caps of grandmothers. Would you accept this as the purpose of your life?
I would not. I would seek for something better to do with my life. The moral is that a purpose is not yours until you choose to accept it. Purpose is not something than be imposed anyway. Your purpose is what you choose for it to be, whether or not intelligence influenced your design.
Do something worthwhile with your life regardless of facts fall outside of your control. If there is an intelligent designer, isn't that what he or she would want you to do? And if there is none, does it really change anything about what you should do? (Hint: It does not.)
I did a simulation to answer that question. When there was no death in the simulation, the population was dominated by primitive individuals. This made it harder for the more advanced individuals to find suitable mates, and it held back the average fitness of the population. When I included death in the simulation, both the average and maximum fitness in the population advanced much faster.
Most mutations occur during conception, or soon thereafter. Death makes room for the next generation to bring another wave of changes, even if the local resources for sustaining life are limited. So, however counter-intuitive it may seem, there is actually pressure for natural selection to preserve death.
The trillions of cells in your body all work together to give you life. Each one plays only a tiny role, but together they produce something extraordinary: you! You are like a cell in the life of humanity. Your role may be small. It may seem to you to be insignificant, transient, or expendable. But your life is an opportunity to contribute to the good of the whole.
Every cell in your body eventually dies and is replaced. Does that mean the cell had no hope? Perhaps it died with no hope for itself, but the cell did not live for itself. It lived for you. Hope is not found in elevating one's self to a state of immortality. We call cells that do that "cancer". Hope is found in working as part of some cause greater than one's own self.