What would be different If we walked on four these days?
In: Biology
There’s a couple of key benefits to being bipedal. Our heads being directly above our midline allows us to have a larger, heavier brain – if we continually had our heads out past our bodies, the strain would be too much on our necks.
Secondly, moving two limbs primarily to move reduces our top speed, but is a more energy efficient way to propel ourselves for long periods. Humans evolved primarily as pursuit predators, where we don’t outrun our prey, we outlast it. Many animals can beat us in a race once, but while they flag and fire from the efforts, we can continue on and will catch them.
Edit: To clarify your final question which I missed first time round… Obviously the hunter/pursuit predator aspect isn’t much of an issue these days for the vast majority of humans. But it’s the first point that would be problematic for us. You can get a feel for this easily – get down on all fours, and then try and keep your head up so you can see forwards. You’ll tire your neck out extremely quickly. It’s not a comfortable position to be in.
Some early ape/hominid had a mutation that led to them walking more upright. They had the most offspring, who were also more successful at producing offspring, and so on.
Huh? Just imagine how weird it would be to still walk on 4 legs.
You wouldn’t be able to see over countertops to order a pumpkin spice latte,
Or drive a car properly.
Or think about the neck pain you would get when walking some time and always force your head upwards.
Very unpleasant.
We could have stayed on 4 but being bipedal became more advantageous. It allows for running mechanics that are better suited to distance running. Sure most quadripeds are faster than us in a sprint, but most of them also tire a lot faster than we do. There are other factors at play too(sweat, hairlessness, cooked food) but being bipedal also contributes.
Additionally you need to be bipedal in order to be able to throw a significant distance, which greatly helps with hunting. Even gorillas who are mostly bipedal and way more muscular have a fairly pitiful throwing ability in comparison because they lack the mechanics for a good throwing form.
There’s credible research that our bipedalism, and subsequent availability of our hands to do other stuff while walking or standing upright, is if not caused by at least heavily correlated with our growth in intelligence as a species. So, to put a minor twist on your last question; I think its reasonable to state that we wouldn’t be having this conversation if the genus homo never started walking upright, or many conversations at all.
Number 1 I think is that bipedal walking is super duper duper energy-efficient. Like, **humans are some of the best long-distance walkers on earth.**
This obviously helped a lot when we first left dense forest and started living in more open terrain, but we really came into our own with *Homo rectus* – it’s no coincidence that the first human ancestor to walk totally upright was also the one to explode out of Africa, reach as far as China, and prosper for like 1 million years. Forget big brains, our ability to travel for long distances while burning very little fuel is our first and best unique trait. (Okay, brains were a part of *H. erectus*’s success too, but you get my point).
*H. erectus* was a hunter, not just an eater of occasional meat. And they probably hunted the same way many modern hunter-gatherers in Africa do: they walked an animal to death. Walk up to an antelope, and it runs away. Follow it, it runs away. Follow it… it can always out*run* a human, but we can straight up follow it until it’s too exhausted to move. Walk up to it, spear in the heart.
A human can beat a horse in a marathon. I think we don’t talk about humans’ freakishly energy-efficient walking as much as we should
Heat.
In the savannah we needed to dissipate heat. Most animals do not do this because they don’t sweat. But us having our torso above the grass where a breeze could pull heat away allowed us to go long distance.
This is one no one else mentioned. Big brain, seeing over the grass, efficient long distance travel, and maximum exposure to breezes for evaporative cooling. We are well designed for sure.
Our crania would be smaller – constricted by the fact that the hole for the spinal column would stay at the back of the head (like it is for gorillas), rather than the bottom like it is for humans. Therefore, we’d probably not be ‘human’ at all, as we understand it, due to different brain development.
Childbirth would be much easier though. Bipedalism resulted in drastic changes to the shape and size of the pelvis, making childbirth much more painful and risky.
What no one has mentioned is that we evolved in grasslands and standing upright allowed us to see further. It also has advantages in temperature regulation.
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