Right after the Big Bang, tiny primordial black holes could have been born. Stephen Hawking believed they didn’t grow: the hot plasma around them moved too fast to fall into such a small capture region (the Schwarzschild radius). New research turns this idea on its head. It turns out these holes can satisfy their hunger with neutrinos — ghostly particles that ordinarily pass through matter as if through a void.

Thanks to inflation (an idea from Alan Guth) and the expansion of the universe, at a certain point neutrinos start behaving like prey, falling into the black hole. This allows primordial holes to gain a mass of anywhere from a thousand to a million solar masses. The surprising conclusion: these grown-up holes could turn out to be the very dark matter that holds galaxies together.

Now the James Webb Space Telescope can glimpse the traces of these feasts in distant galaxies, and gravitational wave detectors (LIGO) can catch the ripples from their mergers. Dark matter may not be so dark after all.