Sir Martin Rees believes if extraterrestrial life exists it’s probably robotic, which makes Sir Martin Rees the greatest person ever. Now if we can just alert this otherworldly machine intelligence of our whereabouts and it can come down to Earth and eat our tiny, delicious brains, things will be perfect.

I’m only half-kidding.

The best-case scenario is that humans will ultimately evolve into a combination of carbon and silicon, becoming human-ish rather than human. The worst-case scenario: extinction. After all, those who aren’t busy being born are busy dying. In Rees’ excellent Nautilus piece on the topic, the astronomer points out that any life in the inhospitable environs of outer space has probably already successfully transitioned into that of conscious machines. An excerpt: 

Few doubt that machines will gradually surpass more and more of our distinctively human capabilities—or enhance them via cyborg technology. Disagreements are basically about the timescale: the rate of travel, not the direction of travel. The cautious amongst us envisage timescales of centuries rather than decades for these transformations. Be that as it may, the timescales for technological advance are but an instant compared to the timescales of the Darwinian selection that led to humanity’s emergence—and (more relevantly) they are less than a millionth of the vast expanses of time lying ahead. So the outcomes of future technological evolution will surpass humans by as much as we (intellectually) surpass a bug.

There are, after all, chemical and metabolic limits to the size and processing power of “wet” organic brains. Maybe we’re close to these already. It is remarkable that our brains, which have changed little since our ancestors roamed the African savannah, have allowed us to understand the counterintuitive worlds of the quantum and the cosmos. But there is no reason to think that our comprehension is matched to an understanding of all key features of reality. Scientific frontiers are advancing fast, but we may sometime “hit the buffers.” There may be phenomena crucial to our long-term destiny that we are not aware of, any more than a monkey comprehends the nature of stars and galaxies.

But no such limits constrain silicon-based computers (still less, perhaps, quantum computers): For these, the potential for further development could be as dramatic as the evolution from monocellular organisms to humans. By any definition of “thinking,” the amount and intensity that’s done by organic human-type brains will be utterly swamped by the cerebrations of AI. Abstract thinking by biological brains has underpinned the emergence of all culture and science. But this activity—spanning tens of millennia at most—will be a brief precursor to the more powerful intellects of the inorganic post-human era.

This will be especially true in space, which is a hostile place for biological intelligence.•