Evolution Q&A: Will humans one day fly?

A nice man named Ahmad Fares asked me a question about evolution. I will take this as a sincere request for information, and so will take the time to give a thorough answer.

Ahmad's Tweet

Before I give my complete answer, however, I would like to address you directly, Ahmad, about the bigger picture of your goals with these questions on Twitter.

You’ve told me directly that you do not believe in evolution, and that your point behind these questions is to “cast doubt” on the theory. While I respect the idea of questioning orthodoxy in science, I have to tell you that your specific questions don’t actually accomplish this goal very well.

I can tell that you think they are very clever and very profound. The problem, however, is that you do not seem to understand the theory that you are commenting on. For anyone who actually understands the theory of evolution (regardless of whether he believes it or not), your questions merely come across as uninformed.

To make myself more clear, I will make an analogy. Imagine that I said the following to you: “If Mohammad lived in 600 A.D., then he could not possibly have written the book of Genesis. Doesn’t this call the entire religion of Islam into question?”

Your response would probably be complete incredulity. The assertion is a ridiculous one, based on completely incorrect assumptions about what Islam actually teaches. Your answer would (rightfully) be: “No, of course it doesn’t call Islam into question!”

It is important that you take a moment to think about how annoying and frustrating that kind of assertion would be (about Islam), because your questions about evolution come across exactly the same way to scientists. They are not thought-provoking. They are not profound. They merely reflect a lack of understanding.

Now, to help you to understand specifically why your question comes across that way, I will delve into the details and answer your question for you.


Q: Did evolution stop? [I will address the wings and flying thing in a separate section below]

Let’s start by getting an accurate image in our minds about what the process of evolution really is like. It’s not, as many people suppose, a continual process of improvement or even a continual process of change.

Evolution is an interaction between two things: random variation and selection.  If you have an organism that has adapted well to the environment that it lives in, then according to the theory of evolution, there is no reason that it will change its average characteristics over time.

The basic mechanisms of evolution will still be there.  In other words, there will be constant mutation and random change within the population. But, if the organism is well-adapted to its environment, most of these random changes will either be neutral, or they will make the organism function not as well. If it is neutral, then this change in genes might gradually drift through the population but it will not dramatically alter the nature of the organism. Of course, if the random change is undesirable, then it will eventually get weeded out.

In a situation like this, the process of evolution hasn’t “stopped” — that is to say, both random variation and selection are still happening — but there is no pressure for the species as a whole to change its make-up over time.

This is an important distinction, because when you ask a question like “did evolution stop?” it conjures up a notion as if there is some kind of master “switch” that is being flipped on and off to drive evolution. That’s not the case. The underlying mechanisms of evolution are always happening. In a stable environment, there may be no perceptible change in the genes of a species over hundreds of thousands of years.

On the other hand, something may happen that will suddenly change a random trait that was once undesirable into something that is more desirable.  If that happens, then there can be very sudden change in a species over a very short amount of time.

The classic historic and known example of this is the famous “beak of the finch” that Darwin talked about.  You have a bunch of finches on an island, and their beaks vary widely in strength and size. All of them survive quite happily. Suddenly, something happens in the environment that makes the shells of their eggs much harder than they used to be: a chemical in the environment, let’s say, as an example. Suddenly, all of the birds with smaller or weaker bills quite simply die, because they are not able to break out of their shells to hatch. Within a generation, the average beak size in the population doubles.

That is an example of how a sudden change in the environmental circumstances can lead to sudden change in the traits of a species.

But remember, as long as the finches were in a fairly static and fairly hospitable environment, there was no pressure for a change in beak size: there was nothing in the environment that said that one beak size was any better than another beak size. As a result, there was no movement in the average beak size of the population.

What drives shifts in the average traits of a population is the environment. But the forces of evolution are always there, whether there are continual “shifts” in a population or not.

So: No, evolution never stops. But whether it results in average shifts in the traits of a population depend on how that species interacts with the environment. Starfish have remained essentially the same for millions of years, because their environments have not pressured them to change at all.

Q: Will humans one day in the future have wings and be able to fly?

I’d like to start with a simple issue of terminology: humans will not have wings and fly because we use the term “human” to refer to a specific genus and species that exists right now, and that quite definitely does not have wings or fly.

I think you meant something else, though. I think what you are really asking is: will it be possible that over time, there will be an ancestral line that connects humans to a future species that has wings and is able to fly?

That is a more interesting question, but the difference in wording is an important one.

Purgatorius and the PrimatesTo make an analogy: According to one evolutionary theory, about 65 million years ago there was a small furry creature that we call purgatorius. Purgatorius was rodent-ish with little hands and a long body. It looked a little like an animal that we have around now that is called the lemur.  In fact, purgatorius has a family tree that over time split into many sub-groups, including lemurs, gorillas, and humans.

Even if we were to suppose this theory were correct (and I assume that you do not, but just for the sake of argument!), would one say that “purgatorius eventually gained intelligence”?

No, that would not be the correct way of describing it.

Purgatorius never gained intelligence. What happened is that over time, purgatorius evolved into very different species, one of which (humans) has intelligence.

I’m belaboring this point of terminology, because according to no evolutionary theory would it ever be correct to say “humans will one day have wings”.

The correct way of asking the question is: “Will humans one day evolve into a species that has wings?”

Now that we’ve cleared that up, the answer is: who knows!

Certainly, right at this particular moment in time, there doesn’t seem to be any reason to assume that we would.

But 65 million years ago, there was no reason to assume that a lemur-like furry thing would eventually evolve in a species that had language and culture.  The fact is, there is no way of predicting a future like that.

Let’s take a moment to speculate in more detail, however.

What would it look like? How would it play out?

There would have to be some selection pressure for bodily speed and altitude, for one thing. There would have to be a reason that people who could jump higher and farther had better chances to reproduce and survive. So maybe we can imagine some kind of new alien or unknown predator that would kill off all of the slow people. Or perhaps something would happen that would make people who spent more time jumping would be healthier and would live longer.

This kind of thing would mean that over time, humans with stronger limbs, lighter bones, and perhaps a more aerodynamic body shape would reproduce better and live longer, and gradually would make up more and more of the population.

In this situation, we can imagine that small mutations that might otherwise have been neutral might now be advantageous.  Maybe people with bigger hands, allowing them to be used to flap and keep themselves in the air longer, would now be able to live longer and have more children… thus meaning that more people in the next generation would also have larger hands.

Thus, over thousands of years, there would be pressure for the average traits of the human population to drift:  the average hand-size in the population would increase, the average body-weight or bone-density would become less, and so on.  Eventually, we would become a species that could take a single leap and glide for several yards before landing. And eventually, over time, we would flap our wings.

A lot of fantasy, right?  Of course it is.

But, there are key points to be found in that fun little bit of science fiction I just outlined for you.

Key Point #1: There has to be something in the environment to make it an advantage to jump higher or move faster, for the whole thing to get started. Without an environmental pressure for there to be changes, the changes won’t happen.

Key Point #2: It’s not like there will suddenly one day be wings. Thing move through transitional forms. There will be human descendents that jump very high, then human descendents that glide, long before there will be human descendents with wings.



This has been fun, and I’ve enjoyed taking the time to answer your question for you. If you have more questions, I will be more than happy to answer them for you.

But in conclusion, I want to also emphasize what I said from the beginning: if your goal is to call the theory of evolution into question, then you simply need to learn more about evolution. The types of questions that you are asking do not accomplish that goal.

You are asking basic, elementary-student level questions that have obvious answers.  If your goal is to learn those answers, then I’m here to help.  If your goal is to challenge evolution, then you have a long, long way to go.