Bear Sphere

and with your help it can rack up 700k notes on tumblr in 2024

fun fact: butt-cheeks are one of the things that make us superior to other animals okay note that other apes do not have butt-cheeks

okay don’t quote me on this because I only did sixthform-bio and I’m sure of forgotten loads of stuff but here’s the down-low

back when we were evolving from ape to human, one of the most important things that happened was when our spine started meeting our brains at a sort of 90 degree angle instead of like 45 degrees, which meant that we could straighten up and walk on two legs which was a pretty rad development

except alas oh no our muscles weren’t built to allow us to walk around on two legs because that requires a sort of twisty motion of your hips as opposed to whatever the fuck it is everything else does AND SO ape-people started evolving with longer, narrower waists so that our bodies could twist with every footstep and we could strut along the fashionable catwalk that is neanderthal evolution

but then once this had happened, people realised that we had an advantage over other animals and we would be better at chasing and killing them but we weren’t very good at running

so that’s when we developed the glutenus maximus which is a really badass-sounding name for the muscle in your derriere which helps us to support our spine in an upright position so we don’t get tired, and helps the legs to rotate nicely so that we can run, and has a nice big fat storage around it to help us get energy so that we can run

and that, basically, is the butt-cheek

Humans actually have quite a lot of intramuscular fat relative to some other species–I’m used to mice, which don’t bother, for example; neither do rabbits, which are so infamously lean that dining too heavily on them can be bad for human health. Of course, neither species relies much on endurance. Fast twitch muscles, which are good for sprinting and darting, tend to be powered by glycogen availability even within species; by contrast, slow twitch and highly oxidative muscles that are used over sustained exercise are generally powered by intramuscular fat.

(I am reading an interesting thesis tonight that also notes that relative to horses, dogs have more intramuscular fat in hindquarter muscles–exactly what you would expect to see in the context of intramuscular fat as a local fuel for endurance running, since dogs are–like humans–adapted for long distance persistence hunting.)