Researchers wonder if ancient supernovae prompted human ancestors to walk upright

Researchers wonder if ancient supernovae prompted human ancestors to walk upright
A new paper from a University of Kansas researcher suggests bipedalism arose when ancient supernovae caused lightning that burned Earth's forests and prompted human ancestors to walk upright. Credit: NASA

Did ancient supernovae induce proto-humans to walk on two legs, eventually resulting in homo sapiens with hands free to build cathedrals, design rockets and snap iPhone selfies?

A paper published today in the Journal of Geology makes the case: Supernovae bombarded Earth with cosmic energy starting as many as 8 million years ago, with a peak some 2.6 million years ago, initiating an avalanche of electrons in the lower atmosphere and setting off a chain of events that feasibly ended with bipedal hominins such as homo habilis, dubbed "handy man."

The authors believe atmospheric ionization probably triggered an enormous upsurge in cloud-to-ground that ignited around the globe. These infernos could be one reason ancestors of developed bipedalism—to adapt in savannas that replaced torched forests in northeast Africa.

"It is thought there was already some tendency for hominins to walk on two legs, even before this event," said lead author Adrian Melott, professor emeritus of physics & astronomy at the University of Kansas. "But they were mainly adapted for climbing around in trees. After this conversion to savanna, they would much more often have to walk from one tree to another across the grassland, and so they become better at walking upright. They could see over the tops of grass and watch for predators. It's thought this conversion to savanna contributed to bipedalism as it became more and more dominant in human ancestors."

Based on a "telltale" layer of iron-60 deposits lining the world's sea beds, astronomers have high confidence supernovae exploded in Earth's immediate cosmic neighborhood—between 100 and only 50 parsecs (163 ) away—during the transition from the Pliocene Epoch to the Ice Age.

"We calculated the ionization of the atmosphere from which would come from a supernova about as far away as the iron-60 deposits indicate," Melott said. "It appears that this was the closest one in a much longer series. We contend it would increase the ionization of the lower atmosphere by 50-fold. Usually, you don't get lower-atmosphere ionization because cosmic rays don't penetrate that far, but the more energetic ones from supernovae come right down to the surface—so there would be a lot of electrons being knocked out of the atmosphere."

According to Melott and co-author Brian Thomas of Washburn University, ionization in the lower atmosphere meant an abundance of electrons would form more pathways for lightning strikes.

"The bottom mile or so of atmosphere gets affected in ways it normally never does," Melott said. "When high-energy cosmic rays hit atoms and molecules in the atmosphere, they knock electrons out of them—so these electrons are running around loose instead of bound to atoms. Ordinarily, in the lightning process, there's a buildup of voltage between clouds or the clouds and the ground—but current can't flow because not enough electrons are around to carry it. So, it has to build up high voltage before electrons start moving. Once they're moving, electrons knock more electrons out of more atoms, and it builds to a lightning bolt. But with this ionization, that process can get started a lot more easily, so there would be a lot more lightning bolts."

The KU researcher said the probability that this lightning spike touched off a worldwide upsurge in wildfires is supported by the discovery of carbon deposits found in soils that correspond with the timing of the cosmic-ray bombardment.

"The observation is that there's a lot more charcoal and soot in the world starting a few million years ago," Melott said. "It's all over the place, and nobody has any explanation for why it would have happened all over the world in different climate zones. This could be an explanation. That increase in fires is thought to have stimulated the transition from woodland to savanna in a lot of places—where you had forests, now you had mostly open grassland with shrubby things here and there. That's thought to be related to human evolution in northeast Africa. Specifically, in the Great Rift Valley where you get all these hominin fossils."

Melott said no such event is likely to occur again anytime soon. The nearest star capable of exploding into a supernova in the next million years is Betelgeuse, some 200 parsecs (652 light years) from Earth.

"Betelgeuse is too far away to have effects anywhere near this strong," Melott said. "So, don't worry about this. Worry about solar proton events. That's the danger for us with our technology—a solar flare that knocks out electrical power. Just imagine months without electricity."

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More information: Journal of Geology, DOI: 10.1086/703418
Citation: Researchers wonder if ancient supernovae prompted human ancestors to walk upright (2019, May 28) retrieved 20 September 2019 from
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May 28, 2019
it cant be scientifically possible for a supernova to evolve humans, their just too powerful

May 28, 2019
Supernovae take only a few months to reach peak brightness and fade away in couple of years. This means that if one changed evolution of humans, it should have killed all 4-legged humans very quickly and leave only 2-legged ones alive. Why this would happen solely to humans, not to elephants or other animals?

May 28, 2019
Two people who didn't understand the article.

It sounded bogus to me, from the headline, but after reading it I realized all they're doing is building on a very old (I'm talking 1970s-80s) set of ideas about how the patchy savannas would have produced selection pressures that favored bipedalism.

So, no matter what the press release seems to imply, what they're talking about are causes for the formation of savanna landscapes. That's all.

The rest is absolutely not new, and is solidly-based. Probably somebody in their lab picked up an introductory paleoanthropology undergraduate textbook and said something like "hey, look at this!" Because it's basic, basic, basic. And not new.

May 28, 2019
Historically - before fire departments and other modern conveniences - my little section of Texas wasn't forest but more of a southern end of the North American great plains. Trees couldn't grow in abundance here because grass fires typically passed through every five to ten years. Portions of the African savannah were similarly fire-prone. There are species of grass specifically adapted to this, and have been for millions of years. It makes perfect sense that a species living in that environment would adapt to fire as well.

Why do the authors need a supernova for that?

May 28, 2019
Are we 100% sure the supernova wasn't the target?

May 28, 2019
The authors and many other contributors are drawing a link between an increase in carbon in the atmosphere-which volcanism can be ruled out of as the main player due to the isotopes found in said carbon layer- to increased wildfires due to something - which coincides with a supernova - which can cause lightning strikes to happen more frequently in theory (unobserved in anyone's lifetime, who knows) - to yeah, what wailuku1943 said above, selective pressure from loss of habitat leading to more walking and upright behavior. Makes sense.

May 28, 2019
To what wailuku and SciTech dudes said - yep...
However, the one thing I really appreciated in this article was the super clear description of lightning's action...
And Bloodtail - it's "they're", not "their".
And JRi - elephants were already tall enough to see over the grass...

May 28, 2019
A clever idea that on its face seems valid. It will be interesting to see how this holds up under peer review.

May 28, 2019
Can't believe what passes for science these days. This article is in the realm of fairy tales and fiction. Not clever ideas. Really stupid ideas.

May 28, 2019
I vaguely remember a recent article or two posted here, last year maybe.
The researchers claimed evidence that pre-hominid apes already were displaying the physiology for bipedalism before permanently climbing down into the grasslands?

That would support this articles conclusion that our potential ancestors lost access to trees to climb back up into.
Also, the best advantage hominids ever had against predators & competing foragers?
Was our ancestor's willingness to use fire.

After a wildfire?
A lot of tall grass & bush would be cleared.
Allowing standing apes to see a long distance.
Both for detecting predators,
also to see scavenger birds revealing carcasses.

After the worst of a fire?
Hopefully, bipedalers could outrun?
Searching for dead animals & cooked vegetation.
The hominids would find a safe camp from prowlers wary of smouldering ground.

If a predator did approach?
The band could have chucked hot sticks, that would flare up as they flew, scorching the careless predator.

May 29, 2019
Can't believe what passes for science these days.

Increased electrons in the lower atmosphere causing increased lightning then fire then savvanah.
Is a totally reasonable conclusion.
How else then do you expect a quick evolution of humans from ape to man? There are no other theories really.

May 29, 2019
I find it hard to believe that anyone would publish this. To say it is a stretch is being kind. It is all speculation and assumption and it establishes nothing as fact. If I had tried to submit such a poor product in college it would have been immediately and soundly rejected. Terrible, terrible 'science'.

May 29, 2019
Care to like, actually criticize anything they actually said in the paper, @el? Or is this just another troll?

Jun 01, 2019
Notably this is Mellott's hobby horse since decades - last time he published on a putative cosmological event causing the extinction of Megalonodon [ https://en.wikipe...n_Melott ]. I would not expect anything coming out of it, even the author's are tentative (so I was spared reading the article): "The new authors suggest that this wildfire increase, which has previously gone unexplained, may be due to a nearby supernovae 7 to 8 million years ago. Evidence for a supernova then, however, is still preliminary, though Fields said it may emerge in the future." [ http://www.astron...-bipedal ]

The general problem with crying wolf shows up in statistics too. The likelihood Mellott's horse will make the finish line decreases with every time he whips it, he should adjust for data fishing with the same type of hypothesis. But who knows, maybe he will get lucky any day.

Jun 14, 2019
Care to like, actually criticize anything they actually said in the paper, @el? Or is this just another troll?

Yeah the comments here are often from

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