Feb 17
Could Humans Develop Blowholes by the Year 4000?
An introduction to fractal evolution
In one of my favorite scenes from Waterworld, Kevin Costner’s character is wrestled to the ground while one of his captors pulls aside his right ear to reveal that — gasp — he has gills!
I saw Waterworld when I was 13, and a question has stuck with me ever since: could humans develop something like gills if the Earth was covered in water? In retrospect, this wasn’t idle speculation, as the world has since warmed and sea levels have risen. But even if the Earth didn’t become a full water world, but rather a wet world, one covered in lakes, how would humans adapt?
Consider the Dolphin
First of all, we wouldn’t develop gills. Instead, we’d have blowholes because that is what happened to one of our ancestors who eventually evolved into dolphins. Dolphins evolved from a wolf-like creature 50 million years ago whose nose drifted to the top of its head over the span of 15 million years. That’s right, dolphins have dislocated noses on their heads, and we have the fossil evidence to prove this:
Consider Pakicetus, the “wolf-like” ancestor of dolphins:
Notice that Pakicetus looks like an ordinary mammal with a snout. Snouts are the protrusions on the face containing both noses and mouths. If you have a dog or cat, you’re also familiar with the wet furless part on the snout, an organ called the rhinarium. The rhinarium is a separate sense organ for smelling through touch. Humans don’t have snouts, nor do we have rhinaria. Instead, our nose is sort of in the middle of our face, somewhere above our mouths and below our eyes, which is similar to Rhodocetus, which came after Pakicetus:
Rhodocetus exists sort of halfway along the evolutionary tree between Pakicetus and dolphins. As you can see, its nose is closer to its eyes. Likewise, given that our noses are sort of halfway up our faces, are we possibly a species in transition to something like dolphins, with a nose on our heads?
While I’m being a little facetious, my ultimate question is not about if we could develop blowholes, but when. Could humans develop blowholes by the year 14 million, which is directionally the length of time it took for Pakicetus to turn into dolphins? The answer is a resounding yes since it already happened that way. My real question is whether it could happen in 4000 years, i.e., does evolution move that fast? A quick back-of-the-envelope calculation seems to indicate so.
A Quarter-Million Neurons Per Generation
Imagine yourself walking down the street, past random strangers. Everybody has different heights, different gaits, and also different nose positions. It seems like the standard deviation in nose position is 1 cm. Divide that by 16, which is the number of generations separating you from the average person. That means our nose moves up or down 1/16th of a centimeter every generation. If it takes 10 cm to place the nose atop our heads, then multiplied by 16, it should take 160 generations, which if multiplied by 20 years per generation, comes to 3,200 years. By the year 5250, we could become quasi-mermaids.
Where did I get 16 generations? That’s roughly the number that crops up every presidential election when the media traces candidates’ family trees. For example, the media discovered that George W. Bush was Barack Obama’s 10th cousin, once removed, and that John McCain was his 22nd cousin, twice removed. And in researching this essay, I found a blog post by Brad Tempelton titled “Everybody is your 16th cousin.” So, 16 it is.
I once shared my napkin math with a biologist, who humored me for a bit, but I could tell from his body language that I was making him uncomfortable. Later that evening, I Googled whether there was a speed limit to evolution, and the first thing that came up was a Wikipedia entry called rate of evolution. I was hoping to find some answers inside, but it turns out that the speed of evolution is unsettled science.
Now, if you’re a scientist, you are probably groaning or rolling your eyes by now. If you’re an evolutionist, you might even suspect that I’m talking about something dangerous, possibly along the lines of the aquatic ape hypothesis, which is the idea that we came from the ocean. I once casually mentioned the aquatic ape hypothesis to my primatology professor, and her facial expression was like I had said something taboo during Thanksgiving. Clearly, in some circles, you should never talk about politics, religion, or the aquatic ape hypothesis.
But I looked into it, and it’s unclear what the speed of evolution should be. While my napkin math was a stretch, there are some calculations that aren’t so far-fetched. For example, our brains quadrupled in size between 3 million years ago to 200,000 years ago. By one calculation, a quarter-million neurons were added to the Homo erectus brain every generation.
Can you imagine that every generation has a quarter-million more neurons than the previous? If the generation time is 15 years (assuming 10 for Homo erectus and 20 for Homo sapiens), that’s 15,000 neurons per year, or about the number of neurons that fit into a period at the end of this sentence.¹ It’s a tiny amount, but over enough years, it takes us from Grog to Einstein.
When I said that the speed of evolution is unsettled science, I didn’t mean to imply there is nothing written on the subject, but rather that it’s too early to tell. Most of the debate is about the shape of evolution, not its speed. One of the first major conceptional breakthroughs on the subject was the introduction of punctuated equilibrium by Stephen Jay Gould. According to this theory, lifeforms typically have a stable relationship with their environment until something drastic happens, causing a leap in that species’ evolution, followed by a return to stability.
Another piece of settled science is the mutation rate in humans, which is between 0.0001 and 0.000001 times per gene per generation. These numbers paint a picture of a slow and random process, which is hard to reconcile with the fact that humans have also gained a quarter-million neurons per generation.
If we’re adding a quarter-million neurons per generation, is it possible that Gen Z is smarter than Millenials? There is a famous phenomenon called the Flynn effect, which describes how worldwide IQ scores have been increasing by 0.31 points every year since the invention of the tests. But if you read the Wikipedia entry on the effect, there is no mention of the possibility that we’re getting smarter on a genetic level. And yet that would contradict a simple trendline in brain growth since Homo erectus.
Which side is correct? Is evolution fast or slow? Part of why evolution seems slow is because this is what evolution looks like:
A gradual model of evolution goes from A to B and divides over time. So, in my brain example, we take the brain of Homo erectus, subtract it from our current brain size, then divide it by the time between those two, et voila, we have the rate of evolution, which as I mentioned above, is a quarter-million neurons per generation. In some sense, this is literally what happened.
Fractal Evolution
But if you dig into the “rate of evolution” Wikipedia entry, evolution might be a lot trickier than that. There I noticed a new concept from Philip Gingerich, which I call a “fractal rate of evolution,” which makes evolution seem “fast.”
I put “fast” in quotes because it’s not a matter of speed, but one of wobble, which is the third or fourth derivative of distance depending on how you look at it. If you remember from High School physics, the first derivative of position is velocity, and the second derivative is acceleration, but what is the third? If you were a curious student like me and asked your teacher this question, you’d learn that it’s called “jerk,” which makes intuitive sense. If you’re in the driver’s seat and put your foot on the gas, you’ll notice how the car jerks, which represents a change in acceleration.
What about the fourth derivative? According to Wikipedia, the term is called “jounce,” which is nonsensical to me, so I prefer wobble or jitter, which sort of represents the jittery feeling you get just as you’re about to press on the accelerator, ostensibly because you’re about to embark on an exciting road trip.
All kidding aside, this wobbling is likely what happened between Homo erectus and us. The movement wasn’t linear, but more like a random walk. A random walk is how a drunk person walks home. They stumble left and right, seemingly at random, but they’re clearly headed somewhere. And as it turns out, random walks are the best way to model the stock market. On some level, it does seem like the stock market goes from A to B, but the closer you zoom in, the more it looks like it wobbles all over the place:
Likewise, it’s not like the brain added a quarter-million neurons every generation in a smooth line. Instead, there were hops and detours along the way, like a fractal. To explain fractal thinking, consider this riddle: what is the length of the British coast? It might seem trivial. All you have to do is wrap a really long measuring tape around the coast of Britain, right? But to get an accurate answer, wouldn’t you have to specify a resolution? Should the measuring tape wrap around every crag and boulder? Should it wrap around every molecule?
This riddle was created by Benoit Mandelbrot, who also coined the word “fractal.” In fractal geometries, the boundaries of shapes are infinitely complex. When you zoom in, you can see that the length of the British coast grows and grows. If you want a truly accurate measurement, you might even have to wrap a measuring tape around every quark.
Likewise, in fractal evolution, resolution matters. For example, if you examine the length of horses between now and a million years ago, you’ll find a difference of, let’s say, a few centimeters. Then, if you divide that delta by a million years, you’ll sort of get the “speed” by which the horse’s size grew or shrank. But if you change the timescale to a few generations, the speed oddly seems to increase.
Biologist Aris Katzourakis identified this pattern in retroviruses, which Wired highlighted in “Evolution is faster and slower than you think”. But even without looking at the evidence, fractal evolution makes intuitive sense. There are all sorts of height variations among humans today, but when comparing the average height today with the average height a hundred generations ago, the difference would likely be smaller than the difference between my height and yours. Wobbly metric, indeed.
So, just how fast is recent human evolution? If you take the temperature at a convention of evolutionists, the answer might put you to sleep. Some of the most common and “exciting” examples of recent human evolution include the ability to metabolize alcohol and the persistence of lactose tolerance in adulthood. But I would argue that there is a lot more biologically separating Einstein and Jesus than lactose tolerance.
Sexual Recombination vs. Mutation
Human genome sequencing has only been around for two decades, which has limited our imagination to monogenic traits, such as eye color or malaria resistance. I would argue that the most interesting things about us are polygenic. A polygenic trait is one based on multiple genes. I cannot find the exact source where I saw this, but human height seems to be directionally determined by 10,000 genes. Likewise, intelligence is extremely polygenic.
So, instead of focusing on genetic mutation to explain recent human evolution, we should focus on sexual recombination. Recombination is so much faster at producing human change than mutation. Waiting for a mutation to confer an advantage is like waiting for a particle of space debris to collide with a satellite. The odds of a mutation being not only valid but interesting are like the odds of a bullet hitting a bullet.
Variation through sexual recombination has to explain the random walk that we see in the fossil record. Recombination is the drunk, invisible hand that stumbles its way forward through a changing environment. Our bodies and minds aren’t waiting for some random mutation, but are instead wobbling at each generation to test the limits of what’s possible.
So, will humans develop blowholes by the year 4000? Well, we will probably develop a technological solution to rising sea levels a lot faster than evolution will make us mermaids. But so far, based on my being an armchair evolutionist, nothing out there says we couldn’t.
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