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Is the human brain really the most complex object in the universe?

There are 86 billion neurons in your brain, roughly the same number as there are galaxies in the observable universe. Whether the mind is more complex than the cosmos, however, is up for debate

By Thomas Lewton

21 February 2024

D84PBB NGC 6888, the Crescent Nebula.

The Crescent Nebula: more complex than the human brain?

Reinhold Wittich/Stocktrek Images/Alamy

BACK in 2012, neuroscientist Christof Koch wrote in his book Consciousness: Confessions of a romantic reductionist that the human brain is “the most complex object in the known universe”. Given that there are about 86 billion neurons in a brain, connected up in ways that we are only beginning to unravel, this seems intuitive. But when I put it to David Wolpert at the Santa Fe Institute in New Mexico – created in the 1980s as a hub for the budding field of complexity science – he doesn’t see it that way. “It’s almost farcical to entertain that we are the most complex system in the universe,” he says. “The question is actually wrongheaded.”

Despite this, I persevere. Surely, there is some common measure of complexity that can be applied to all kinds of intricate systems? After all, if you squint, clusters of galaxies and the filaments that connect them look like tangled circuits of neurons. There are even roughly the same number of neurons in the human brain as there are galaxies in the observable universe. This similarity in form may have something to do with general laws through which complexity emerges, says Ricard Solé at Pompeu Fabra University in Barcelona, Spain. Or it may not. “Coincidentally, that might appear in both systems, but that doesn’t mean anything,” he says.

Besides, complexity isn’t defined by components and their interconnections. It is the idea that the whole is more than the…

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