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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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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