The other week The Washington Post’s Speaking of Science blog addressed the question: “Dear Science: Why aren’t apes evolving into humans?”
This is a variation on the more common “If humans evolved from monkeys, why are there still monkeys?” that I covered here a while ago, so I was naturally interested. But before I even read the piece, I found myself exasperated by the linear ape-to-man illustration accompanying it. The art was attributed to a Post artist, drawn, apparently, specifically for this article! How disappointing that this misleading cliché was the best they could do!
Can we PLEASE all stop using this graphic human evolution stories?? https://t.co/7gZwpgrTX4— Stephanie Keep (@keeps3) June 27, 2016
Clenching my teeth and vowing to get over the lazy artwork, I waded into the article itself. The piece is set up as a Q&A to “Science.” It starts: “Dear Science, Why are there no hominins [(species more closely related to modern chimps than to modern humans)] left on Earth? If evolution is ongoing and species are always changing and adapting, shouldn’t we see new human-like species evolving from apes, even if the old ones died out?”
Author Sarah Kaplan starts her response so well that I was sure this would be an unqualified “Well Said!” post. After breaking the news that humans are themselves apes, she writes: “First of all, the creatures we call apes are our cousins, not our ancestors. Which would make it very hard for them to evolve into something like us.”
Then, Kaplan quotes anthropologist Matt Tocheri of the National Museum of Natural History’s Human Origins Program who says:
Asking why an archaic human isn’t evolving from gorillas today is like asking why the children of your cousins don’t look more like you. Those creatures have been on their own lineage for 10 million years. You can’t go back up that lineage and back down again.
Kaplan and Tocheri are reminding us that living apes are just as evolved as living humans—we’ve just evolved on different paths. Chimpanzees, our closest living relatives, didn’t stop evolving 6 million years ago when their lineage diverged from our own. Asking why they haven’t evolved into humans makes as much sense as asking why humans aren’t evolving into chimps, or why dogs aren’t evolving into cats. Kaplan’s comment about living apes being our cousins and not ancestors is the key to understanding why there are still chimps if we evolved from chimps—namely, we didn’t. Chimps and humans both evolved from a common ancestor. They are, as Kaplan says, our cousins—not ancestors.
Then Kaplan really hits her stride: “It’s easy to think about evolution as a linear, progressive drive toward greater and greater complexity, something that started with single-celled amoebas and ended with us. But evolution doesn’t have a destination, and even if it did, humans are certainly not it.”
Yes! Woo! Right on! (So why did you accompany the article with an illustration of linear evolution? I know I said I’d get over it but I can’t, it drives me bonkers.) But right when I was ready to celebrate, things started to get a little bumpy. The first sign of trouble came from an extremely unlikely source: Nina Jablonski, a paleoanthropologist from Penn State who starred in the fabulous HHMI short film The Biology of Skin Color, who says:
Evolution is about survival under particular conditions, and random mutations. There’s a big element of chance and certainly no element of direction…Living things are just trying to adapt to the contingencies of life in their environment. [emphasis added]
Obviously, we know that organisms do not try to adapt. But unfortunately, the piece not only goes on to echo Jablonski’s blunder, it also steps on another classic misconception landmine. Kaplan writes:
The diversity of hominins during the earliest stages of human evolution showed us how several species tried to do that [adapt to their environment]. For example, it’s thought that Australopithecus afarensis (Lucy’s species) evolved human-like hips that let them walk on two feet because it let them carry things—a useful skill for collecting food on the savanna. [emphasis added]
Sigh. No. Australopithecus afarensis did not evolve the ability to walk on two feet because it let them carry things, just as birds did not evolve wings to let them fly. Teleology can be very hard to avoid, but it is possible—and necessary—for science educators of all stripes (writers, teachers, researchers) to avoid it at all costs. What Kaplan should have written is something like this: “For example, it’s thought that Australopithecus afarensis (Lucy’s species) evolved hips that enabled them to walk on two feet a trait that gave them a strong selection advantage because it meant that their hands were free to carry food, tools, or weapons across the savanna.”
In the same teleological vein, Kaplan says that with the advent of tools, hominin species didn’t have to “choose” between different types of teeth. As my paleoanthropologist friend Briana Pobiner said to me in an email exchange about the article, “enough with the agency!” When it comes to evolution, organisms are not consciously trying or choosing anything. Because honestly, if we could choose, how many of us wouldn’t choose to be sloth-octopus hybrids of awesomeness? Wait… just me?
A final hiccup has Kaplan saying of modern great apes that as they live in forested environments, they “have no need for human bipedialism” (should be: human bipedalism would not give modern apes a significant advantage in their current environments), but Jablonski wraps things up on a high note:
When we look at our ape relatives today, they’re just fine being ape-y…of course, that’s predicated on the hope that modern humans don’t chop down their forest completely and entirely deprive them of their natural habitat. But that’s a different issue.
So what’s my overall verdict? Well, I’m glad, of course, that an article on human evolution got attention. It’s always good to remind the public that humans are apes and that apes are not a lower form of humans. However, I’m disappointed that such common misconceptions were displayed so prominently. And of course, I’m still not over the accompanying art.
Can someone please make a good, branching graphic and make it available on Wikimedia Commons? I'll send cupcakes. https://t.co/7gZwpgrTX4— Stephanie Keep (@keeps3) June 27, 2016
Anyone want cupcakes?
Are you a teacher and want to tell us about an amazing free resource? Do you have an idea for a Misconception Monday or other type of post? Have a fossil to share? See some good or bad examples of science communication lately? Drop me an email or shoot me a Tweet @keeps3.