If Humans Came From Apes, Why Are There Still Cats and Bananas?

A decade or so ago, I had a great chat with ex-NFL star Herschel Walker about fitness, football, bobsled (he was a 1992 Winter Olympian), and mixed martial arts — at the time, he had just beaten a guy two decades his junior.

We didn’t chat about evolution by natural selection, although in retrospect, perhaps that would have been more interesting. Last week, Walker — who is now running for Senate in Georgia — trotted out his version of an old evolution-denial saw:

So let’s start with a practical example that might resonate right now. Below is a graph from Our World in Data, my favorite site on ye olde interwebs.

As you can see, in mid-2021, a number of Covid variants were circulating in the United States at the same time. Granted, they were ultimately “outcompeted” by faster spreading Delta, which was in turn outcompeted by Omicron. But now a subvariant of Omicron is spreading, diversifying the Covid landscape again. The point is that multiple variations from a common ancestor can exist at the same time.

And current pandemic aside, there are at least seven disease-causing coronaviruses found in humans. All of those evolved from a common ancestor that existed a long time ago. The common ancestor is gone (just like the original Covid-19-causing variant might be), but those progeny are alive and well. (If viruses are alive at all.)

Our global pandemic is natural selection at hyperspeed — evolution can go fast or slow — and a takeaway should be that multiple organisms that evolved from a common ancestor can exist at once. (I’m repeating this point because last week’s newsletter was on how repetition is important for countering misinformation.)

Humans and chimpanzees, for example, both evolved in different ways from a common ape ancestor. As with the common ancestor of modern coronaviruses, that common ancestor no longer exists, but its descendants — humans and chimps — still do.

If Humans Came From Apes, Why Are There Still Cats and Bananas?

The more closely related organisms are, the more DNA they share. That’s why humans share 99% of our DNA with chimps, a bit less with cats, a bit less still with mice, and even less (but still plenty) with bananas. Go back far enough, and all life shares a common ancestor; and yet here we all are, cats and bananas together.

Part of the misconception embedded in Walker’s statement is the idea that evolution proceeds along a linear trajectory toward some final, best form. (If it did, it clearly would have stopped with therizinosaurus.) As in: “Why do we need monkeys when we made it to humans?!” But that isn’t how evolution works. Evolutionary theory doesn’t suggest that apes should transform into humans (and chimps, and other apes) and disappear upon transformation.

While it is technically true that “humans came from apes,” it’s a bit confusing to put it that way. We are apes — just a particular kind — and so are chimps, orangutans, and gorillas. Those respective family trees all branched from a common ancestor.

As biologist T. Ryan Gregory put it in a great paper titled "Understanding Evolutionary Trees":

A billion or so years ago, Canada and Australia were side-by-side in a supercontinent (“Nuna”), which no longer exists.

We hairless apes may yet cause other apes to disappear, but, imo, let’s not. There is no necessity for an evolutionary ancestor to vanish just because part of a lineage goes off on another developmental path.

I have two siblings, and while they descend from the same parents, there is no reason we can’t exist at the same time, different as we are. (My younger brother is much taller; it’s annoying, but it’s probably fine if he still exists.)

The same goes for our children’s children’s children. In the past, modern humans even coexisted with other types of humans, like Neanderthals. Those two tangoed, and it left marks in the DNA of many people alive today (including me).

Have Your Laugh, But Then Get Earnest

I’m not sure there’s much we can do for Herschel Walker at this point; but, to quote biologist T. Ryan Gregory’s "Understanding Evolutionary Trees" paper again:

And I think we should teach those lessons — like how you can use your own family tree to help understand evolutionary concepts — at any age, earnestly. It’s easy to poke fun at Herschel Walker, but what we do after that is what counts. I think engaging with questions about fundamental pillars of modern science is important, and not always trivial.

We can laugh at people who say that the Earth is flat — as Kyrie Irving did, to much coverage — but we who laugh might ask ourselves: “How do I know the Earth is spherical?”

This has been pretty much settled since ancient Greece. And yet, your answer (mostly likely) is that you outsource this judgment to the consensus of the scientific community. That is frequently an excellent decision-making heuristic. But perhaps you’d like to have a deeper answer. I minored in astronomy in college, and can fairly say that proving that Earth is a sphere isn’t so trivial that we should simply laugh at someone who asks for proof of something that defies their daily experience. (If, of course, they are doing so sincerely. It’s unclear to me if Irving was just trolling.) At the very least, after we laugh, we should think about what we ourselves know.

This isn’t to say that there aren’t simple proofs of Earth’s curvature, but can you think of any offhand? Perhaps that you’ve seen pictures of Earth from space? Photos are two-dimensional; that could just as well be a flat disk as a sphere.

Personally, I find epic photos like the one below, with perspective showing the curvature of the Earth, to be quite persuasive.

Then again, the photo atop last week’s newsletter was of a shark swimming on a flooded highway, and it looked real, even though it’s just an old photoshop job. I guess my point is that, while it’s ok to have your laugh, also have some curiosity, and ask how you know what you know.

It might be interesting for you to learn, and helpful for teaching others.

On that note, here are ten simple proofs of Earth’s curvature. Several, like #2, are accessible, and fun to teach. But some of them involve — if not some measure of scientific savvy — trust. For more on that, here’s an interesting article in Physics World on how trust is the missing component in fighting flat-Earth theory.

If you enjoyed this post, you might like last week’s newsletter on misinformation — why it works so well, and how to combat it with a "truth sandwich."

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For more wide-ranging thoughts, you can follow me on Instagram or Twitter. As always, thanks for reading.

Until next time…

David