Good morning, John. I was so sorry to hear about your back. I hope that you are feeling better. It sounds terrible. I did a bunch of research on herniated discs because that's kinda my thing. I figured I'd tell you what I learned because it's fascinating, and it seems like maybe the reason that humans so often have bad backs stretches all the way back to the advent of bipedalism. We'll get there, but first we need to talk about your back.

So we're vertebrates, which is great, we have a spinal column that's protected by bone. But you still want to be able to like bend and twist and stuff because otherwise you can't do TikTok dances. So the vertebrates' solution to this problem is lots of individual vertebra with these little things in-between them that are really hard but kinda squishy at the same time. Discs, they're called intervertebral discs. Not intervertebral. Intervertebral. Because they want people to look stupid. It's basically a very firm but squishy ring, and inside of the ring is contained a gel. Now a buncha things can happen to that little disc to make it wear out like you could just get older, that-that's part of it. Injury, also a big one, but also just putting a load on it, not directly where it's aligned usually. So if you're standing up, like, it's-it's pretty much like where the weight is supposed to be. But if you're sitting down, especially if you're like slouchin' and your your butt's a little forward, that can put some extra pressure on those lower back intervertebral discs. And then there's also genetic stuff like the kind of collagen proteins you make and the shape of your spine and vertebra all matter. And if that hard squishy disc breaks down enough, eventually the gel can leak out from inside of it and that's a herniated disc, and it's painful and sounds very bad. 

All of this is to say you and I have very similar genetics and similar lifestyles, so now I'm scared, uh, and I'll be watchin' out for the warning signs. But here's the thing: Chimpanzees, gorillas, orangutans (our three closest relatives) none of them have this happen to them. So the obvious question to ask is why? What's different? And there's two main hypotheses.

The first one is that, like, chimpanzees do chimpanzee stuff. Like their bodies are evolved for the lifestyle that they live. And at first, this hypothesis was lookin' pretty good because people who lived a more hunter-gatherer lifestyle had less reported back pain. But the more we looked into that, the more it seemed like it was actually the the reported part of reported back pain, not the back pain part that was rare. People were just living through their pain. And indeed we have now seen lots of evidence of ruptured discs in the human fossil record, so it seems like it's been a thing the whole time, which is not to say that your lifestyle does not affect whether or not you might get a ruptured disc; It absolutely does.

But the other hypothesis is that there's just something not great about human backs. We're seven million years into the shift to bipedalism, but it is a relatively large shift. Like it's a totally different thing to have all your body weight stacked on the vertebral column rather than sort of hangin' off of it like it would for a dog or even a
chimpanzee to some extent. But how do you test for this? Well, there's some scientists who looked at a buncha human vertebra that had evidence or not evidence of having hemorrhaged discs. And the ones that had hemorrhaged discs were much more likely to look more similar to chimpanzee vertebra. So it seems like: People who have vertebra with similar morphology and characteristics to chimpanzees are more likely to get ruptured discs. Almost as if their spines are more ancestral? Now this is wild. And it was a pretty small study and it only looked at Europeans, so you can't take that much from it. But they actually did a follow-up study with 3D scans and one of the authors said this and I quote, "The humans that have intervertebral disc herniations tend to have a shape that is statistically indistinguishable from chimpanzee vertebrae."

So John it may be that your vertebra shape is statistically indistinguishable from that of a chimpanzee. And you might think, "Okay, eh, there was plenty of time to evolve our way out of chimpanzee vertebra." But then in a separate paper, some of those researchers found that you could actually swing too far toward, like, optimized for bipedalism and you get a separate condition. It's called spondylolysis and it causes stress fractures in the spine, so that's also bad. So maybe we are not yet optimized for bipedalism or maybe bipedalism is just really difficult to optimize for in our sort of body type. Like kangaroos seem to have it figured out. Also, all birds are bipedal and they seem like they're doing fantastic.

Anyway John, I'm sure that this didn't help with your pain at all, but it's pretty much all I know how to do in a situation like this. I'll see you on Tuesday.