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AstroAlert: Do we walk upright because of ancient stellar explosions?

Hi everyone,
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An interesting, though wildly speculative, new paper suggests that humans might walk upright today because of the explosive deaths of nearby stars millions of years ago.
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Here’s the idea. There’s evidence that Earth has been blasted by supernova explosions many times in the past. For example, there’s a layer of iron found in ocean sediments that’s believed to have been deposited when neighboring stars exploded several million years ago, showering our planet with iron and other atoms created in the stars’ interiors.
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Supernovae, the explosive deaths of massive stars, have lit up the night sky on Earth from time to time throughout its history

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The Crab Nebula is the remains of a massive star that exploded thousands of years ago.

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Here’s the speculative part. The paper’s authors suggest that cosmic rays – energetic atomic fragments – created by a series of nearby supernovae might have altered Earth’s atmosphere when they slammed into it. This in turn could have caused the atmosphere to become more conductive of electricity, which might have lead to more frequent lightning. All this lightning might have sparked wildfires around the world, burning much of the original African forest and creating the savannah environment that’s believed to have contributed to the evolutionary advantage that bipedalism offered our early human ancestors.

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A new paper suggests that nearby supernovae explosions altered Earth’s atmosphere millions of year ago, leading to more lightning.

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That’s a lot of “mights,” “maybes,” and “ifs.” But it’s a novel theory that’s founded on various pieces of evidence, some stronger than others. The author’s themselves acknowledge its highly speculative nature, conceding that “If the lightning-cosmic ray connection turns out to be incorrect, this whole thing falls apart.”
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If you’d like to know more, just click on the links below:
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And if you’re interested, you can also read the original scientific paper, “From Cosmic Explosions to Terrestrial Fires?” published in the Journal of Geology:
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As Mark Twain once said, “There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.”
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Best regards,
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Michael
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