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Exploding stars led to humans walking on two legs, radical study suggests

mosaix

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Exploding stars led to humans walking on two legs, radical study suggests


It was the evolutionary leap that defined the species: while other apes ambled around on all fours, the ancestors of humans rose up on two legs and, from that lofty position, went on to conquer the world.

The benefits of standing tall in the African savannah are broadly nailed down, but what prompted our distant forebears to walk upright is far from clear. Now, in a radical proposal, US scientists point to a cosmic intervention: protohumans had a helping hand from a flurry of exploding stars, they say.
 

Dave

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I have a different idea. I think the lack of hair points to us spending time in water. Standing upright on the bed of a river or lake would be an advantage because it would allow them to walk deeper. I have collected no evidence for my thesis on this yet, but it sounds just as likely as running from forest fires. Come to think of it, a river or lake would be a better place to hide from a forest fire.
 

-K2-

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Well, the point of the article (which I am not defending), pertains to the 'cosmic rays' *snort*, and their affect on weather (lightning), burning down the forests leaving grasslands... IOW, grass high, need elevation to see over it vs. dense woodlands.

Personally, it's another one of those things where a gazillion different things could yield the same results... Sure, you can possibly 'prove' that during that time, cosmic rays, lightning, volcanos, a cave genius and his new invention-- a Zippo, a piece of ice made a perfect lens... whatever... but, bluntly to be sure I would be stunned if we ever knew for certain.

What I can say is... looking over tall grass is a flimsy reason. Numerous species developed better hearing and most of all a better sense of smell to cope with that. What does make sense, though is just a guess on my part, is that by having useful hands instead of feet or hooves, granted a primitive species the ability to walk and use their hands at the same time. Naturally, that's long before chewing gum, so it won't be a factor.

So, my line of thought would have me searching for 'when/why an opposable thumb,' long before standing upright.

Although, I'm still something of a knuckle-dragger. ;)

K2
 

Teresa Edgerton

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I have a different idea. I think the lack of hair points to us spending time in water. Standing upright on the bed of a river or lake would be an advantage because it would allow them to walk deeper. I have collected no evidence for my thesis on this yet, but it sounds just as likely as running from forest fires. Come to think of it, a river or lake would be a better place to hide from a forest fire.
Are you familiar with the aquatic ape theory, Dave? Most anthropologists have not accepted it—many deride it—but it does have its followers. Aquatic ape hypothesis - Wikipedia

I read Elaine Morgan's book about it many years ago, and I thought she made some good points.
 

Venusian Broon

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I note that the article itself states, right at the end: "The researchers concede that more research is needed to understand if cosmic rays really do drive lightning." Riiiighhht. :)

I'd think that climate factors would have more of an influence - if it's much wetter climate maybe all this extra lightning would have no effect. Because even without extra cosmic rays, it's not like there's not going to be lightning.

I'm less negative on the "seeing further I grasslands" aspect of standing up for our far distant relatives. We were never faster, stronger or more ferocious than the predators around about as, so gaining an advantage of seeing further and therefore getting a chance to do something about it could have helped. Then they would have probably thought about doing something with these spare limbs and digits that standing caused.

The aquatic ape theory is now quite an old one @Dave, it seems to go in and out of fashion on a regular basis. There does seem to be quite a lot of evidence that Homo Sapiens was definitely fond of the beach, but I believe we were practically hairless a lot earlier than that. Isn't their another theory that we lost hair so that we could perspire and therefore become extremely efficient long-distance runners. (A viable way of hunting)
 

Dave

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I wasn't aware of the aquatic ape theory (maybe subconsciously) but I think it makes sense. It is as least as likely as escaping from fires.

And I hadn't read the whole article. The solar wind that causes aurora is thought to sometimes cause a kind of thunder when the positive charge from above meets the negative charge from thermally rising air from below. So, in that respect
the 'cosmic rays' *snort*, and their affect on weather (lightning),
isn't too far fetched.
 

Venusian Broon

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I believe it has been proposed that cosmic rays can potentially propagate lightning....but it feels to me like one of those very "glam" hypothesis that has yet to be proved.
 

Brian G Turner

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Hmm. I think I'll class this as "interesting research that takes an irrelevant marketing hook for marketing purposes".

The idea of a more ionized atmosphere I don't think has any bearing on whether humans walked upright or not, and the aquatic ape theory still seems the lead contender for explaining a whole slew of physical characteristics - not least why we might have adapted to walk upright.
 

Dave

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I believe it has been proposed that cosmic rays can potentially propagate lightning....but it feels to me like one of those very "glam" hypothesis that has yet to be proved.
People have heard the rumbling sounds and clicks and pops, and have associated them with lightning, but apparently, no one has managed to record it.
The Sound of Aurora
Aurora are unpredictable and difficult to see anyway. The arctic is still relatively unpopulated. Then you'd need to have the right weather and to be in the right place at the right time.

However, to say that some undocumented increase in exploding stars occurred, resulting in such an increase in this activity, that the lightning then caused an increased number of forest fires on Earth, well that has got to be stretching.

The idea of a more ionized atmosphere I don't think has any bearing on whether humans walked upright or not
That too!
 

tegeus-Cromis

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Well, we already have documented proof that cosmic rays can influence human evolution. After all, they turned Reed Richards into Mr. Fantastic, Sue Storm into Invisible Girl, Johnny Storm into the Human Torch, and Ben Grimm into the Thing.
 

Robert Zwilling

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I always wondered about the emergence of the modern body. If large scale fires or other large scale events caused a change in the plant world which radically changed our bodies I would think that many other species also experienced profound changes. There were droughts, floods, ice ages creating stress for the plants as they couldn't move out of the way. The Messinian age seems to be a good time to see what other animals were doing or changing but I couldn't find much in the way of change. The Miocene ended around the time the walking started. At some point there were around 100 species of apes with a far ranging variety of diets. The birds reached their greatest diversity during the Miocene. Crocodiles and caimans were doing quite well, there was even a filter feeding crocodile with small teeth. All kinds of modern day animals flourishing. Maybe it was sort of like the Cambrian explosion for modern animals. Changing landscape, everyone running, slimmer legs developing. The horses started 50 million years ago and branched in many directions with all kinds of leg and body configurations. Seems like only 1 horse species made it to modern day Earth and it wasn't a direct route, like humans. Supposedly the legs developed in response to avoid being caught while running from everything trying to eat it. Maybe it was all the running people had to do to avoid being eaten, same as the horses. With all the different configurations perhaps chance had a role in selecting the version with the skinny legs. Looking at it from another direction, loss of hair, body mass, bone mass, all point to illness rather than advancement. During the end of the Messinian, the Mediterranean dried up then filled up again. Maybe the pureness of fresh water wasn't so pure during this time, polluted by run offs through mineral rich areas, brackishness, not the best drinking water. Combine dubious water with the randomness of the selection of the last man standing and the one with the thinned out body and fast running legs won out.
 

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Or perhaps, in the case of humanoids, sexual selection of which this one trait remains with us to this day. Naturally, this is all just guessing and logical assumption on my part.

Today, though perhaps even more defined, although more subtle (not as pronounced compared to others), when a man stands up straight, pulls his shoulders back, straightens his neck and lifts his chin, women and men take notice. Though it used to be the norm, today it seems like parents don't teach their children posture. In fact, in my circles the guys complain about needing to have their suits custom made because the back of the collar and shoulders are set for someone who stoops, so, they get a bulge of material across their shoulders with off the rack.

Immediately, when a man walks into a room with everyone else lazily hunched over and stands up straight, most eyes turn to him as the one in authority, that exudes confidence, aggressiveness, and power. People are very wrong if they don't think it makes a huge difference with women. In kind, simply by pulling your shoulders back, chest out and chin high confidently fixing your gaze on their eyes when you speak to people... instead of being some demure wilting flower, a woman will instantly project a dominance over other women and some men in the room. Most men appreciate it, some don't *shrug*... and that is today.

So, I strongly suspect, simply by standing more upright than your peers 'back then,' very possibly established a dominant posture that would have been noticed. If so, and if viewed as strength, then sexual selection would have resulted in an evolutionary shift very quickly.

How quickly? In my 20-years of hunting, portable tree-stand use as the norm for bow hunters had just started being utilized by the majority of hunters. The first couple of years it was so easy, most deer didn't 'look up,' that it was almost unfair. In roughly 3-seasons, it all equalized. Some deer I'm sure/know learned, others were clearly born with that natural trait to 'look up.' In perhaps ten seasons, so roughly five generations, the majority of deer looked up... and wise hunters left the trees and went back to the ground. Obviously, that's 'natural selection' of the fittest.

Sexual selection I suspect, might advance as quickly, if not more so regarding altering common traits causing an evolutionary shift.

K2

EDIT ~ Addition: Considering this line of thinking, it's actually not that unreasonable. Many animals, birds and even fish 'posture' whether competing for mates or to establish dominance. Those creatures with necks, will very often (though not all species) raise their heads and stiffen their frame. Even apes. So, I would assume that coupled with other factors determining natural selection, sexual selection might be influenced by those early humanoids simply tending to stand up more often than not.
 
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thaddeus6th

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Got there before me, Teresa.

One of the arguments for the Aquatic Ape Theory is that even a few months (from memory, read this some years ago now) into growth, dolphin and human embryos are practically indistinguishable, and the organ set-up is very similar indeed.

Not saying I subscribe to the theory, mind, just that there is at least something behind it.

Brian, it's like a history book. The title is the catchy hook for the general reader, the subtitle is actually historically relevant :p
 

Robert Zwilling

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Dinosaurs started on all fours and went on to two feet, eventually flying off the ground. I see animals like squirrels, chipmunks in the wild and meekrats and prairie dogs from videos, standing up quite often. I see rats and mice running around, but rarely see them standing. They appear to be similar animals. Perhaps the ones who stand more are more relaxed and not as worried at being killed as the ones who don't seem to do much standing in the same areas. The standing ones are somewhat concerned about human activity, you can't just walk right up to them, where as rats and mice take off immediately when spotted by a person. The rats and mice seem to reproduce at a faster rate. In the wild, the squirrels and chipmunks sit up when eating while the rats and mice don't. One monkey wrench is that the prairie dogs are basically extinct while the rats and mice have managed quite well in their interaction with humans. Rats and mice can live anywhere, climb anywhere, but prairie dogs have to live underground, where they are running around on all four feet. Does the more appendages one has off the ground or can get off the ground, have a bearing on how long survives on this planet?

We spend far more time eating than having sex, it doesn't seem unlikely that eating habits would also have profound impact on how animals behave. If looking up saves deer from being killed by very stealth means while trying to eat, does standing up enable squirrels and chipmunks to experience less pressure because they can see "it" coming so they can reproduce less often, but rats and mice that don't stand up, have to reproduce at a faster rate.

It could be argued that our treatment of the planet has worsened because of our reproduction to the tune of 8 billion. Is it our reproduction style that is changing the planet or is it our eating habits and efforts to obtain creature comforts, so that we can reproduce more freely, the force that is changing everything. Our eating habits are changing the lifestyles of millions of different kinds of animals, I don't think our sexual actions have anywhere near the same impact.

Rats can stand up when being aggressive, puts forward a bigger image. Standing up could be a permanent form of protective aggression.

For people, standing up frees up the hands for a whole world of uses that don't exist when running around on all fours. Sex may be what causes reproduction, but it might not be the driving force that changes everything. If you don't eat, your not going to be strong enough to reproduce, but reproducing doesn't mean you are going to eat, could even have the opposite effect. Horses went in the other direction going from having multiple digits to just one digit on each foot in order to survive. Is it just chance that determines who ends up running the show and how animals survive that show? Maybe everything is on a limited existence ticket, because no matter how clever or adept one is, the size of natural disasters are basically unlimited.
 

RJM Corbet

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Og trying to balance on three legs while rubbing rocks to make fire: Nuh uh, this definitely isn't the best way to do this. This sucks. So, maybe if I try supporting my full weight on my two back legs, so to use both my front paw hand things ...

Hey, this works, bro!

Hey Zog: wanna see this?

And the idea is there.
 
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