Ancient star explosions could have led early humans to walk upright
S E E D E D C O N T E N T
More than six million years have passed since early humans first walked upright, and it’s still unclear exactly why we made the switch from four legs to two. One popular theory holds that the change was the natural result of an evolving landscape that made it more efficient to walk upright.
Now a pair of physicists have come up with an underlying cause for that shift — and it’s a wild one: Millions of years ago, a series of exploding stars not far away from Earth bombarded our planet with radiation , igniting wildfires that destroyed lush arboreal habitats and forced our ancestors out onto grasslands — where two-legged living made more sense.
“If you’re still using trees a lot, you now have to walk from one to the other — you can’t swing around up there like an orangutan,” said Adrian Melott, a physicist at the University of Kansas in Lawrence and lead author of a paper about the research published May 28 in the Journal of Geology . “If you’re going across the grassland, going on two legs is more efficient than four.”
To learn how stellar explosions, also called supernovas , could have affected the early Earth, the scientists turned to clues on the planet’s surface. They used previous research on deposits of iron-60, a radioactive form of the metal left behind by nearby stellar explosions, to identify a series of supernovas that began about 7 million years ago and peaked about 2.6 million years ago. Then they calculated how radiation from those explosions, called cosmic rays , might have affected life on Earth.
Most cosmic rays penetrate only the upper reaches of our atmosphere. But since the supernovas that researchers focused on were relatively nearby, their cosmic rays would have been powerful enough to reach the ground, knocking charged particles called electrons off air molecules. The scientists believe this change, called ionization, created a cozy environment for lightning strikes, a major trigger of forest-leveling wildfires.
Based on the iron-60 deposits, the scientists calculated a 50-fold increase in atmospheric ionization in the aftermath of one supernova, believed to have occurred about 2.6 million years ago at a distance of 163 light-years from Earth. If their theory is correct, cosmic rays unleashed by the supernova could have driven a massive wave of lightning strikes, igniting wildfires that changed the landscape from verdant forest to grassy savanna.
That’s where bipedalism comes in, the scientists say. Biological anthropologists have long theorized that a change from forest to savanna may have helped prompt proto-humans walk upright. As trees became few and far between, the theory goes, it was more energy-efficient to travel on two legs, giving bipedal hominids a reproductive edge.
The researchers say their theory is corroborated by the geological record, which shows a spike in wildfire byproducts like soot and charcoal in soil beginning 7 million years ago.
But the scientists acknowledge that their theory isn’t airtight. The weakest link, Melott said, is the connection between cosmic rays and lightning, which is difficult to investigate when the events leading up to a lightning strike are so poorly understood. “You can’t have instruments measure lightning because you don’t know where it’s going to happen,” he said. “It’s very difficult.”
Even if supernovas did play a role in bringing bipedalism to our ancestors, experts say it’s unlikely to have been the only factor. By the time the supernova activity peaked, about 2.6 million years ago, “you have some things walking around that are quite bipedal already,” said Isabelle Winder, an evolutionary anthropologist at Bangor University in Wales who was not involved in the research. She cautioned that the so-called “savanna hypothesis” for bipedalism, which dates back to the 1920s, is considered by some scientists to be an oversimplification.
“Increasingly, we look at the environmental evidence and we go, ‘No,’” she said. “We might be seeing one fraction of the complex whole.”
Melott and his coauthor agree — to an extent. “Bipedalism had already gotten started,” he told the Guardian . “But we think this may have given it a strong shot in the arm.”
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Not exactly 2001 version of the story, but it does seem possible.
Does anyone see a flaw?
They offer a possible explanation that would select for bipedalism. Seems to me this hypothesis will be, at best, factored with other hypotheses over time to produce a theory for bipedalism. My natural skepticism does not find this to be a likely dominant explanation for bipedalism.
After reading all of the varying theories, I don't think it was one singular thing that made us walk upright. There were various necessities to do so, so I think the more early man needed to be upright, the more our spines and legs evolved to fit that need. Could some event have hastened that along, I think that is a possibility, but the need had to be there first.
I think there are a multiple factors which led us to be bipedal. But I'm with TiG in that I do not find supernovas to be a major explanation.
Or maybe, getting hit by supernova blasts mutated us and gave us superpowers? In this case, it was the "power' to walk upright?
“If you’re going across the grassland, going on two legs is more efficient than four.” So why does every other animal that lives on grasslands not walk on two legs ? They all walk and run faster than humans on four legs. The true reason we evolved to be Bipedal is when we became more intelligent we started to use weapons, and tools. The ability to carry tools, weapons, food, and water as they traveled about gave those who could walk on their hind legs an advantage over those who couldn't. Then through millions of years the more adept at Bipedalism thrived and interbred will those who weren't died out and slowly humans became more and more upright to the point we are today. We evolved to carry the possessions we used to give ourselves a survival advantage because survival advantages are what shape evolution.
... is very much open to discussion...
Your theory makes a lot of sense
exactly, sort of, but after the real conversion to being bipedal.
which is why I believe in the aquatic ape theory - it answers more questions without creating more questions.
During the hottest period on earth, most living things were driven to the waters edge.
No one knows how long this period lasted, but apes standing in deep water would be forced to be bipedal.
Hair below the neck became a disadvantage.
Tears and sweat remove excess salt.
Why do we shade our eyes and squint? reflection of light off the water.
Why does our heart rate change when we free dive?
Why do we have evidence of a long lost second inner eyelid?
Why do we have so many common biological features in common with other marine mammals?
One theory does not answer every question,
but some theories answer many, many more than the Savannah theory or Biblical nonsense.
The reason I believe the Tool and Weapon Theory is no other animal is built or moves like humans. Our Skeleton is highly specialized and the one other major difference between humans and other animals is no other species uses tools to the extent we do. We've been making and using tools and weapons for millions of years while a very few other animals might use a rock or stick as a tool but they never modify them and no other animal could do what we do with tools and weapons. When I see people working and using tools I see an animal that was purpose built to use tools as an extension of themselves the same way an animal with digging claws evolved to dig.
That is a good explanation, too. One that should be considered along with many others.
Our skeletons are also built to swim and dive. No tool theory ( which defies evolution ) can account for that.
Why are we naked when other primates are not?
Why are most other aquatic mammals almost hairless?
Are elephants evolving away from being aquatic mammals (likely)
or evolving back towards being aquatic mammals (not likely )
but we have much in common with them ( except for the multiple vaginas, ours simply moved over time )
Why do most women experience a great thickening of their neck hair at the end of their pregnancies? Why do babies automatically cling to moms hair in the water?
Why do some women give birth in a pool without any bad effects on the child?
Why do almost all women recoil involuntarily at the sight of snakes and spiders? Too close a resemblance to giant eels and giant crabs of the prehistoric days?
The aquatic theory explains why we ended up upright and were able to carry possessions.
It's highly doubtful that having multiple possessions caused us to stand up over tens of thousands of years because we needed to carry them.
"So why does every other animal that lives on grasslands not walk on two legs?"
Because every other prey animal has their eyes on the side of their head and can pick up movement of a predator behind them, but for primates with eyes looking forward to see better behind them, standing up and twisting at the waist is more efficient than on all fours and bending the neck sideways and then you would still have your body in the way causing a blind spot.
First it was millions of years and having multiple possessions didn't cause us to stand up, that's not how evolution works. Having multiple possessions (tools and weapons) gave them an advantage in survival and those who had the ability to carry their weapons and tools while they walked around looking for food had the greatest advantage making them better fed and better at protecting themselves and their children. So they survived in greater numbers and had more children who passed on their more upright genetics.
Yeah....savannah mammals run faster than bipedals. Maybe it has something to do with hominids in general, but when was the last time a biped outran a ruminant?
Humans are excellent long distance runners. They may have hunted by running their prey to exhaustion.
They may have stood up to get a better look around.
It's a fascinating subject.
That's a good point, I didn't think of that
I see flaws everywhere, lol
I tend to agree with TIG and Zuksam while these stellar events may have been a part of why we became bipedal it's more likely our bipedalism is a result of many differing factors.
I think that early hominids got tired of looking at the ground. That includes us, along with the rest of the apes.
They also most likely found the could see much further.
The rest of the apes are not bipedal, while they occasionally engage in a form of bipedalism they are normally knuckle walkers/runners. However birds are and depending on your definition so are kangaroos and jerboas
No, it's too late right now. Maybe tomorrow.
One thing that caught my attention was the ionization. Back when my daughter was in middle school, she was able to pick her own science projects.
One year she asked the question "does lightening affect plant growth"?
hmmmm? Good question.
So I set her up with a kit to create 2 sealed plant life environments. (can't think of what they are called right now).
Using 2 gallon capacity gold fishbowls she created sealed environments of plant life. One, however, had constant, 24/7 "lightening". We went to the hobby shop (something kids needs to do more often) and got an electric motor kit with several gear reduction ratios to choose from. That combination was powered by 4 D cell batteries. That was used to create a set of contact points (think old automotive ignitions). Then an electric train transformer provided electrical energy to energize a Ford Model T ignition coil to create a spark every 3/4 second.
The plants in the experiment began as seeds. The comparison of the 2 test groups was amazing. Actually there was no comparison.
Te natural group grew as expected. The lightening group took off like "wildfire". In no time they overgrew the capacity of the fishbowl, hitting the roof and turning back down. She took a daily log with photos.
Pretty convincing experiment.
Her experiment of "do the moon phases affect the weather" was even more amazing, but doesn't fit in here.
Terrariums?
Bingo.
You win, Trout.
YAY, me!
lol
That was a very cleverly devised experiment.
Indeed that was!
Thank you.
She was a pretty clever young scientist.
Her projects won awards for several of her science teachers.
I saw this news in several places, and hesitated a bit before deciding not to seed it. It's a very interesting idea... but it seems awfully tenuous. I'll put it in the back of my mind, and wait for corroboration.
Dear Friend Perrie: An alternative theory is that our ancient ancestors figured out that by walking on two rather than four legs, the cost of footwear could be cut by 50%.
This theory was first proposed by the research, song and dance team of Dolce and Gabbana at the University of Eastern West Virginia at Sacramento Department of Redundancy Department.
In support of this idea are the following statistics:
4 out of 5.
92%.
Once in a blue moon.
Every other Thursday, but never on Shabbos!
You just can't argue with numbers like those.
Mathematically Yours,
Enoch.
Now THAT is a convincing argument!
Dear Brother Bob: Thanks and warmest regards.
Enoch.
Where were you when I was taking Probability and Statistics?
Dear Friend Trout Giggles: I was ringside at Duffy's Adult Entertainment and Men's Calculations Club, watching Forumula's Galore performing a Mobius Strip.
Enoch, Still Watching Figures.
Dear Friend Atheist: You and me both brother.
Smiles and Regards.
Enoch.
That's it Enoch! You nailed it. You can't argue with those numbers!
Tell me, if I bought two pairs of shoes, did I get the third for free?
I like a bargain.
Especially for those of us with two left feet!!
Dear Friend Perrie: If one train going east traveled 451 miles at 60 miles per hour, and another chugging along at 61.5 MPH headed west, which came first, the chicken or the egg?
Some things get lost in history, like the companion right blue suede shoe to my left one.
Enoch, slowing headed out to IHOP.
Could these 'scientists' be of the same ilk as the 'scientists' that claim children had pet dinosaurs ten thousand years ago?
I don't think so. I just think they have a different theory.
The pet dinosaur creation 'scientists' believe the Earth is less than 10,000 years old.
That was a really interesting article SP. Most people don't know that the only true homosapians are Africans. The others came from mixing with other humanoid species like all white people contain about 4% neanderthal while most Asians contain about 4-6% Denisovan genes. But that does not explain all the other variations that we see across the spectrum of the human race. This theory would.
Sometimes I wish I was an "on all fours" type person. My dog can kick my ass in a race.
I just don't like the rummaging for everything with my face idea though.