so you see, humans evolved to be bipedal on account of how our ancestors transitioned from the forest environment to the savannah environment, and in the savannah environment bipedalism was more adaptive because it provides better thermoregulation and allows you to carry things, but most of all because bipedal locomotion is highly energy efficient and energy efficient locomotion would have been very strongly selected for on account of how time budgets are a limiting factor on home range which is a limiting factor on diet quality and breadth which is really quite important
my lecturers have been very clear and very insistent that bipedalism evolved first and then allowed tool use, tool use did not spur a transition to bipedalism, the fossil record is Clear On This Point
and what I do not understand is: if bipedalism is so completely wonderfully energy-efficient and optimal, why are there so few bipedal things? How come lions and gazelles and giraffes and buffalo aren’t bipedal? Why aren’t other savannah species selected for energy-efficient locomotion too?
I am sure there is a good explanation for this but my lecturers have still not provided it and I must know please god just somebody explain this to me or I will die of curiosity
Reasons Why We Have Bipedal Apes, But Not Bipedal Lions, According To My Biological Anthropology Supervisor:
You know when creationists talk about how an eye couldn’t possibly evolve gradually, because half an eye is useless and a waste of resources and worse than no eye at all?
They’re wrong about eyes; a single photoreceptor cell (usually just an evolutionary ‘tweak’ away from a regular epidermal cell with biochemistry that happened to be photosensitive) is actually useful and great, and more is better. If you imagine breaking a modern wing in half and attaching it to a bird, “half a wing is useless” sounds true, but it stops sounding true when you realise that halfway to a wing doesn’t look like a modern bird wing but broken in half, it looks like a slightly enlarged membrane between a limb and your body that gives you just an extra half second of glide time when you jump.
But there *are* adaptations in this class of things, where it’s great if you have full-blown X but shitty to have half-baked X. As you might imagine, they are quite rare, because as the creationists correctly observe, if half-X is maladaptive there is no path to arrive at X through gradual adaptation to an environment. And yet bipedalism is of this class. How?
Well, you wanna know what it looks like to have enough bipedal foot structure that you decide to go adventuring around in the savannah on two feet, but you haven’t got the pelvic structure to make it efficient yet? YOU CAN’T RUN. You are literally incapable of moving faster than a kind of slow awkward lope. Your back kills all the time because your bones are all pointed the wrong way and your back muscles are trying to keep you upright. Your ankle and leg bones take far more pounding than they were ever optimised before and occasionally shatter. You’re unbalanced and ungainly and frankly sort of pathetic, and at very high risk from predators (to repeat: RUN AWAY IS NOT AN AVAILABLE STRATEGY).
Why would anything go through a long gradual process of getting much shittier and then eventually getting better, since evolution can’t plan or foresee? WRONG QUESTION. Whoever told you evolution was a slow gradual constant drift was a dirty rotten liar, just like all your other teachers from when you were twelve. More commonly, evolution involves long periods of relative stability where the organism is pretty much as adapted to its niche as it’s going to get, and then something changes and there’s a very rapid response. Or it involves successful populations dispersing widely over a landscape, then becoming distinct reproducing populations which lost genetic contact with each other and diverging, and then there’s an environmental change and they reconnect and sometimes they happily interbreed and sometimes one of the divergent branches drives the others extinct and disperses itself widely and rinse and repeat.
What happened was, basically:
Hi we’re early hominins and we just love hanging around in trees and we’re proud to say we’ve been hanging around in trees now for a couple million years and we haven’t changed a bit, slightly bigger skulls aside, we’re basically just per- what the fuck? WHAT THE FUCK? WHERE DID THE TREES GO?? WHY IS IT SUDDENLY SO DRY???? oh my God I can see nothing but grass and I am having to walk around on my hind legs all the FUCKING time and FUCK FUCK FUCK THAT’S A LION FUCK PANIC RED ALERT oh okay we’re bipedal now I guess, that was quick, oh well, all fine, carry on
Somehow we survived when a change in environment pushed us into a new ecological niche. The selection pressure was strong enough to make us acquire a really quite extensive range of mods to make bipedalism work, but not strong enough to make us dead.
Of course, “strong pressure to adapt somehow” doesn’t necessarily mean “strong pressure to adapt in this specific way we know is really good”. Early hominins who lived before the forest shrinkage have been shown to have a few bipedal adaptations. We weren’t sure what the hell they were doing with them, so we looked at chimps. Turns out chimps display short-distance carrying behavior - as in, picking up an object and carrying it. They don’t carry tools and can’t move far bipedally, but what they do do is pick up a valuable resource like a choice bit of prey and haul it off with them, away from the group of moneys fighting over the rest of the prey. So before the forests collapsed, there was a mild selection pressure to be able to use only your hind legs for a short stretch so that you could carry something in your arms, and when they collapsed, individuals good at that behavior were better at surviving the savannah and evolution just slammed its foot on the gas pedal until you get obligate bipeds.
So, a species that wasn’t forced into a rapid niche change like that, wouldn’t evolve an initially-painful thing like bipedalism. What about all the other species that made the same change as the same time as us? Eh, many went extinct, that happens a lot with ecological change, but the ones who survived didn’t do bipedalism.
Points to those who said it was about evolution having different starting points to build on, y'all were correct. No matter how awesome and efficient and optimal bipedalism is, evolution only cares about whether the next tiny step in some random direction increases or decreases how many offspring are produced. Evolution “looks” for the NEAREST solution that counts as a solution, not the best solution.
For a species of monkeys that were forced to spend less time in the forest and range wider and already had some variable locomotion abilities, evolution went for bipedalism. Bipedalism may have enabled the future awesomeness of humans with its efficiency and head stability and what have you, but evolution made it happen just because it was the local maxima - its awesomeness is a lucky side effect.
But where monkeys used short bursts of bipedal movements to carry things, another species might use something more convenient for them - say, a lion might pick up and carry things in its mouth, and if there was a selection pressure to be better at carrying the lions might end up with bigger mouths, but “become bipedal” is very unlikely because half bipedal is worse than no bipedal at all.
Basically, monkeys had the preconditions for bipedalism, nothing else did. (Note that this does not make monkeys special - the ancestor of any species with an unusual adaptation, from giraffes’ long necks to penguins’ Arctic-water-proofing feathers, was a thing that had the preconditions for that adaptation when nothing else did.)
Bipedalism didn’t happen because it was awesome, it became awesome because the range of adaptations it supports turned out to be a package that turned into, well, us.
…Notice that we are not actually the only bipedal species. Notice what they mean when they say things like, “Bipedalism leads to the ability to carry things leads to tool use leads to bigger brains”. On a naive reading, it means “bipedalism is a part of the tech tree and once you’ve bought it you can get hands optimised for holding tools”, and if it says this then you are right to be confused as to why perfectly good bipedal emus do not also have spears and control of fire.
When you realise that evolutionary studies is so full of ridiculously many caveats and preconditions that lecturers just omit them and assume you know they’re there, you start interpreting what they say more like, “In a species that already dabbled in just a tiny bit of bipedalism, bipedalism was the only way to go when the niche changed, it was way better for the new niche then the old way of locomotion, and given the likely presence of some proto-tool-like behaviors like throwing rocks or poking things with sticks, it created an adaptive opportunity to better fit this particular environment by improving on the tool behaviours using the new physiological advantages.”
Also god I learned a lot in that hour. Why does time spent *not* talking to biological anthropologists have to be a thing? Talking to biological anthropologists is the BEST.
Epistemic status: my recollection of a conversation an hour ago between me and an academic in this field, any misunderstandings are because I’m an undergrad who didn’t get what he was trying to say.
THIS IS SO COOL
(Why do I not live on a university campus D:)
SO YES and also, I’m going to pull out my Vaclav Smil* for a second here.
Human locomotion is not particularly energy efficient! It takes us more energy to walk or run than it does for most mammalian quadrupeds, but our energy use curves look pretty different from theirs.
If a horse goes for a trot, its trot (like all its gaits) has a U-shaped energy curve. It costs more to trot at slower speeds, goes down to a most-efficient pace, and then comes back up. At a certain point, it crosses over the energy curve for the horse’s next gait, and the horse will (left to its own devices) start to canter or gallop.
Human WALKING has a U-shaped curve like that, but human RUNNING does not, and that is damned strange for a mammal. Our friend Smil says: “the energetic cost of human running is relatively high, but humans are unique in virtually uncoupling this cost from speed”. That particular aspect of things is a direct side-effect of bipedalism: we can vary our breathing in ways that quadrupedal animals (who have supporting legs all attached to their breathing apparatus) cannot. Basically, we are the evolutionary equivalent of cartoon characters who can spin their legs really fast. So we aren’t as efficient at running as a horse who is going at its optimum pace, but we can speed up and slow down and it won’t cost us much, which is not true of the horse.
Not incidentally, this is why many humans practiced (or still practice) persistence hunting. If you are less efficient than that delicious antelope, but you can make it run at its least-efficient panic speed while you trundle along at a nice constant rate, you can exhaust it.
* Smil, Vaclav (2007-12-21). Energy in Nature and Society: General Energetics of Complex Systems (MIT Press). The MIT Press. Kindle Edition.
I’m so glad OP came back and corrected themselves, I was sitting on my hands reading the first part! Omg those lecturers. I mean they’re getting minimum wage but still. Bless their hearts.
The lecturers conflated tool use and tool making. Tool USE is observed throughout the animal kingdom. Tool MAKING is said to be primate-specific (we ignore corvids in this scenario.) note that this isn’t hominid-specific, though. Tool MAKING is not a function of bipedalism; it’s a function of having your hands free. These are two very different things. Now, it’s certainly true that tool MAKING - in the form of shaped bones, flints and stones - postdates bipedalism in the fossil record, but we must note
1. A shaped blade of grass or a shaped branch counts as a tool, and does not reliably fossilise;
2. Behaviour is notoriously bad at fossilising;
3. Scientists must acknowledge the biases of the fossil record in geology and paleontology, so don’t think that anthropologists are going to be allowed to get away with it.So tool-making, like bipedalism, is something that popped up occasionally in our lineage and is still practiced by our living relatives. It became fixed in our lineage, and is distinctive to hominids, but it was not dropped on us by the Hand of God. Very very few things are.
We also note that birds are bipedal, and are something of the original biped. We are kind of hipsters in that sense. (BEHOLD! THE MAN!)
But, you see, birds generally don’t have HANDS.
When you’re looking at something like bipedalism and asking yourself “what does this say about humans?” Then look at other animals, and see what they’re doing. And then come at it from a different angle. sometimes the answer isn’t the feet. Sometimes it’s the hands.
(via slyrider)
[video]
http://archiveofourown.org/works/11002677/chapters/24510663@yarndarling here it is.YES! just. yes. i fucking love steve rogers for shit like this. this is perfect and i love it. and would you be cool if i podficed it?um pLEASE DO?
I will put on AO3 for ease of linkage?
YES! just. yes. i fucking love steve rogers for shit like this. this is perfect and i love it. and would you be cool if i podficed it?
um pLEASE DO?
I will put on AO3 for ease of linkage?
slyrider asked: OMG WYNONNA EARP IS MY FAV
IT’S SO GOOD
ALL THE BEST PARTS OF THE EARLY SEASONS OF SPN, WITH THE BRIGHT LIGHT AND SNAPPY PATTER OF BUFFY, AND WYNONNA ON TOP LIKE A CRANKY, HARD-DRINKING, LEATHER-CLAD CHERRY.
Anonymous asked: *leans in* voltron?? u r voltron watcher??
do stuff while waiting for other stuff
like that sounds intuitive and vague but so much of the day is spent in a period of wait and if you struggle to motivate yourself to do things then this is the best time
waiting for your water to boil? bag up your garbage. waiting for your coffee to drip? wipe down your counters. roommate taking up the bathroom? scoop the cat box. waiting for your food to cook in the microwave? do however many dishes you can while it’s in there.
waiting is the perfect time to do a limited amount of something for yourself where you would be otherwise just standing around doing fuck-all
THIS IS REALLY HELPFUL!
I actually turn this into a game!
“How many chores can I do while the water is boiling for my tea?”
“Can I put away the dishes and wipe the counters before my lunch finishes reheating?”
“Can I sweep the floor AND change the laundry while the dogs are out back?”
You can totally do this! If you make it like a game, also, you will get better at it, and you can be like ‘yes, now I put away the dishes AND wiped out the sink before my water boiled, I am a level 2 Adult!’
YES
There is a certain level of functionality required for this that I at my worst cannot muster, however, this is a GREAT tactic for getting small things done when you are doing sort of okay or better. I do it all the time when I’m feeling all right.
This is especially good if you’re like me and you suffer from on-the-spot mind-numbing boredom while waiting for stuff. Like, once I’m on my feet and moving around I can (usually) stay functional, but God I bore fast. Thus, I do stuff while I’m waiting for other stuff.
(via cthulhu-with-a-fez)
Met a cute girl. She gave me her STI results and said she was “clean”.
I hate that phrase so fucking hard.
I have family with various medical conditions and it doesn’t make them dirty. I’ve also had partners with STIs and you just have to be tested often, use protection and be a little creative. I am negative for STIs and I keep copies of my paperwork but I didn’t even tell her that cuz her response pissed me off so bad.
Now she stopped talking to me. I guess, I’m dirty too? The fuck?
The language you use matters.
Your status is either negative or positive.THANK YOU.
Related rant: I’ve had people flip out at me because I say STI status isn’t an instant dealbreaker as long as we can have an honest conversation about it and what precautions need to be taken. Like, not only is there the shame on people who have them (hence the “dirty” language), but if you don’t immediately reject and ostracize anyone you know who has or had ever had one, you’re a bad person too for not beating up on them? What the hell.
I had a long-term relationship with somebody with HSV2 and when I went to get specialized testing after we broke up, the doctor grilled me on our safer sex practices and then told me that honestly he’d do the tests but he already knew I didn’t have it (and I didn’t). I’ve had several conversations with my sexual health providers related to this - that “just never get within breathing distance of somebody who isn’t ‘clean’” is fallacious and shameful.
Meanwhile, I guarantee you that people are walking around with STIs that are undiagnosed or that they don’t tell people about because of the stigma. My most recent ex-boyfriend lied to me for like 2+ years about an unprotected one-night stand he had with some random person while heavily intoxicated because he was so invested in the image of himself as a person who would ~never do that~ until it turned out there was a very real possibility that he might have something incurable as a result. It turned out to be a false positive, but I got slapped with the emotional labor of coddling him through his shame because he was too self-centered to admit he’d done something to put me at risk.
Hell, when I found out my first girlfriend ever was sleeping with other people and lying to me about it, her defense was that it was cool that she didn’t want to talk to me about it because “lesbians don’t get STDs anyway.”
My ex, who gave me chlamydia years ago (which incidentally my doc referred to as “the strep throat of STIs”), was so insulted that I asked him to get tested before we slept together. His exact words were “the girls I’ve been with aren’t the type to get STDs.” I lit him up, because wtf does that even mean, and he got tested, and by that I mean he FAKED HIS TEST RESULTS because that was easier and less shameful somehow than going to the doctor.
It’s not about STIs. It’s about consent and respecting people enough to be honest with them.
I never even knew the word “clean” could be perceived like that. Damn.
I’m reblogging this because I recently had a partner send me fake STI results and it feels like complete bullshit. Because of this, I got checked out at Planned Parenthood last week. I’m negative for STIs yet I feel lied to. If people could/would openly talk about health concerns then this wouldn’t happen. Please have real conversations about safer sex with your partners.
(via unpretty)
Listen, IDK if I’m on my own here but I’ve just started Wynonna Earp and Wynonna and Dolls need to touch faces (and maybe other things).
My reasons for this include:
Anyway.
TL;DR: Xavier Dolls and Wynonna Earp need to kiss, or at the very least someone needs to direct me to literally any decent fic including that event
the one thing about american gods that i’m
liking is that all the gods who are supposed to be black are black AND dark skinned. like i shouldn’t be happy over a tv show meeting basic casting requirements but still it’s nice.
(via slyrider)