That was no fun. I've come to expect better from Nautilus.

The hypothesis, that past supernovae may have affected life on Earth, is as interesting as it is complex. It is surprising the article, when picking only one hypothesized effect to discuss, chose this one:

>"While no mass-extinction events happened 2.8 million years ago, some drastic climate changes did take place—and they may have given a boost to human evolution. Around that time, the African climate dried up, causing the forests to shrink and give way to grassy savanna."

We could have learned how supernovae may have affected cellular, or even pre-cellular, biochemistry. Instead we got a proposed nexus between supernovae, climate science and human evolution.

The weakness of linking three complex questions, each with large and uniquely-varying uncertainties, shows itself in the article citing only one piece of science: the estimation of when past near-earth supernovae occurred from Fe-60 concentrations in subsea Ferromanganese crusts.

Which makes this bit, buried at the end, even more unbearable:

>"Some scientists think Fe-60 may have been brought to Earth by meteorites"

Unlike the article, which offers it no counterargument, this argument is revealing through its simplicity.

I kind of expected the article to at least mention the end Ordovician Extinction by gamma ray burst theory:

http://arxiv.org/abs/0809.0899 http://arxiv.org/abs/astro-ph/0309415 http://arxiv.org/abs/1409.7049