Recently, some articles have been popping across my feeds that talk about this surprisingly modern human-looking finger bone that has some surprisingly ancient DNA.
I love this stuff. I’ve spent a very large portion of my life reading about ancient humans and human ancestors and offshoots of our lineage. But one thing I realized very early on is that so much of what I was reading just kind of assumed I knew some things.
That’s partly my own fault. I learned that paleoanthropology existed from a magazine cover when I was something like 12 years old. And then I proceeded to never again pay attention in school until about 12th grade. Then when I was about 20 I really started to pay attention to anthropology and paleontology.
Eventually I realized that the people writing the stuff were just normal humans and not these weird super beings.
But by then I was just buying books at random based on what I was excited about or what seemed interesting. I had no baseline or fundamental education in anthropology. So a lot of my reading involved some trust. Not trust that the researchers weren’t being truthful…rather it was trust that after reading and reading and reading, I’d start to build up a lexicon of anthropological terms.
It eventually happened, though I don’t know when.
And these articles remind me of that time. Because they assume a certain level of either understanding or trust that I’m not sure everyone has. But this stuff is awesome so I’m going to tell you about it.
So this finger bone.
If you’re not a paleoanthropologist or somewhere else in the biological anthropology umbrella, or at least an anthropology geek, what on earth would make you see that as remarkably human like.?
I’m telling you it’s a finger tip. Bennett is telling you it’s a finger tip. But if Bennett showed up and told you it was more like the fingers of an orangutan or that it was the tip of a tail…without any background, would you question it?
I wouldn’t. So let’s establish some background context for this.
Primates have a lot of distinguishing characteristics that help us identify something as a primate.
Primates evolved in arboreal habitats and their (our) anatomy reflects that. We have a very broad range of motion in both our shoulders and hips, with a collarbone helping aid that range of motion. We’ve got a generally pretty upright posture. I don’t mean bipedalism even though many primate species tend to stand up on two legs now and again. Upright posture refers to just sitting upright. Without really supporting your upper body with your hands.
Your cat rests its upper body on its hands. So does your dog. You’re probably perfectly comfortable not leaning on your hands. That’s indicative of you being a primate. It frees up your hands to do a lot of other stuff. Like right now. I’m typing this. It would be a lot trickier if I weren’t a primate.
Primates brains have a lot of other stuff going on, too. In loads of primates, the olfactory regions have been reduced. That’s because we rely on our sense of smell a lot less. Our cerebrum is larger than in animals that rely less on vision. We also have stereoscopic vision. Meaning both of our eyes are close-set enough to create a very comprehensive image of what’s going on around us. We have excellent depth perception.
Our brains reflect that. And the orbits of our skulls reflect it as well.
Our hands and feet are some of the most interesting bits. The majority of primates have grasping hands and feet. Humans don’t have feet that are fancy in the same kind of way, and those variations in our feet give some pretty good indications of how individuals we find in the fossil record got around when we compare them to other apes.
Our hands remain more similar, although our fingers are noticeably shorter than the other apes in relation to our thumbs. This is a critical bit.
It allows for a fully opposable thumb. Meaning we can grasp stuff with much more dexterity. This works in conjunction with a bunch of other, more subtle features. Our finger tips have an absurd ability to feel. In fact, our finger tips are considered likely to be the most sensitive tissue around. And just underneath them is the point of this post.
Our finger tips have very uniquely broadened bones in them. These are called apical tufts, and these are a funny thing. Primates have variation in their apical tufts that are generally reflective of how they get around. Spend more time in trees and they’re smaller. Get around quadrupedally and they tend to be larger. But…humans don’t get around quadrupedally.
Our broadened tufts are reflective of our precision grip. It’s a broader surface that helps us manipulate and understand things so acutely using our hands.
And that’s why this little bone is so awesome!
Let’s take another look at that other one, but in the context of the rest:
Clearly this guy looks more like H. sapiens than the rest. But that H. stands for Homo, and we aren’t the only species within the genus. Neandertal is also one of them. You know, the quintessential “caveman” who had gotten such bad press up until the Geico ad campaign?
This apical tuft is closer to modern humans than it is to Neandertal.
Ok so this thing was clearly closer to modern humans, right?
WELL THIS IS WHERE IT GETS EVEN COOLER!
The mitochondrial DNA that researchers were able to gank from this fingertip suggests it’s more closely related to NEANDERTAL. How cool is that? And then looking at their teeth, it’s been found that they resemble Neandertal.
So these dudes, the Denisovans, have more modern looking hands, but Neandertal lookin’ teeth and DNA.
So basically, this little finger bone has told us a TON of stuff. It’s told us that it’s definitely very human like. Morphologically it’s placed squarely within Homo, and more specifically it plops it real close to Homo sapiens–us.
But then the DNA says it’s a bit more Neandertal.
Which, to me, underscores how blurry the reality of different species are in the first place. I mean. Nature doesn’t care. We are the ones who have to go neatly categorizing things.
That gets tricky when you start looking back in time. In the past researchers just kinda compared one thing to the next and made determinations that were revised as time went on and we had more with which to compare it.
Well. Now we have thousands of fossils and have started to get DNA which is showing us just how difficult it is to make these kinds of classifications without biological samples.
This little finger bone, and really everything that the Denisovans have thrown our way, are letting us know just how complex our evolution has been, in even the relatively recent past.