Here's something wild
Picture this: it's millions of years ago, and somewhere in the forests of Africa, our earliest ancestors are swinging through the trees. For decades, scientists assumed that only creatures with ape-like feet—specifically those with super-flexible ankles—could pull off that tricky move of climbing straight up a tree trunk.
Turns out? They might have been completely wrong.
The Great Foot Debate
Let me break down what's been going on in the world of human evolution research. You know how we're always trying to figure out where we came from? Well, scientists estimate that humans and chimpanzees went their separate ways somewhere between 6 and 7 million years ago. That means at some point, we had a "last common ancestor" (let's call it LCA for short)—a creature that was kind of like the great-great-(seriously, add about a million "greats")-grandparent of both modern humans and chimpanzees.
Here's the puzzle: what did this ancestor look like? And more specifically, how did it get around?
The thinking until now went something like this: Chimpanzees have these incredibly flexible ankles that can bend back about 45 degrees—way more than human ankles, which max out around 20 degrees. That ankle flexibility is what lets chimps scramble up vertical tree trunks like furry little mountaineers. Monkeys, on the other hand, were thought to be more "army" than "footy"—they'd use their arms to pull themselves up and weren't quite as skilled at vertical climbing.
This difference in foot anatomy led scientists to speculate about what kind of feet our shared ancestor might have had. Did it look more like a chimp? More like a monkey? The answer supposedly mattered for understanding how our family tree evolved.
Enter the Sooty Mangabeys
But here's where things get interesting. A team of researchers from Ohio State University decided to take a closer look at some sooty mangabey monkeys living in the Taï Forest in Ivory Coast, West Africa. These aren't your typical lab monkeys—they're wild, going about their business exactly as they have for millennia.
The researchers, led by assistant professor Luke Fannin, set up cameras to capture exactly how these monkeys moved. And what they found was kind of jaw-dropping.
These monkeys don't have those super-flexible chimp-like ankles. But here's the thing—they can still climb vertical tree trunks just fine. How? They're doing it through their midfoot. Fannin measured as much as 46 degrees of flexion in the monkeys' midfoot joints while climbing—almost identical to what chimpanzees achieve through their ankles.
"It's a functional equivalence," Fannin explained. "You can't rule out vertical climbing just because something doesn't have a chimpanzee-like foot."
In other words, there's more than one way to climb a tree. And that changes everything about what we thought we knew.
Why This Matters for Human Evolution
Let me get a little more serious here for a moment, because this actually matters quite a bit for understanding where we came from.
One of the big questions in human evolution is how we went from moving around in trees to eventually walking upright on two legs—bipedalism, as the scientists call it. Figuring out what our early ancestors were doing in the forest is crucial to understanding that transition.
If scientists assumed that only chimp-like feet could handle vertical climbing, that shaped their theories about what the human-chimp ancestor must have looked like. But now? Now we know that a creature with more monkey-like feet could have been perfectly capable of climbing too.
What's neat (and a little frustrating for scientists) is that this finding actually clarifies some things while making others more complicated. As senior author Scott McGraw put it: "What adds clarity, but also makes the broader picture more fuzzy."
But here's the part I find most fascinating: we're still connected to those tree-climbing days of our past. Some modern hunter-gatherers are still excellent climbers, and while we humans mostly rely on flexible ligaments and tendons rather than specialized foot bones, the ability is still there in us. Somewhere deep in our bodies, we carry echoes of an arboreal past.
The Bottom Line
So what does this mean for human evolution research? Basically, scientists can stop ruling out certain possibilities based on foot structure alone. An ancient ancestor with monkey-like feet could have been climbing just fine—and that's an important piece of the puzzle we didn't have before.
Sometimes science is like that. We think we've figured something out, we're pretty confident in our assumptions... and then some monkeys in a West African forest prove us wrong in the best possible way.
I don't know about you, but I find that pretty exciting. Every time we look more closely at the natural world, we discover something new about ourselves.
Now if you'll excuse me, I think I'm going to go appreciate my own flexible midfoot.