Cheer up, the post-human era is dawning

Artificial minds will not be confined to the planet on which we have evolved, writes Martin Rees

The far future will bear traces of humanity, just as our own age retains influences of ancient civilisations. Humans and all they have thought might be a transient precursor to the deeper cogitations of another culture — one dominated by machines, extending deep into the future and spreading far beyond earth.

Not everyone considers this an uplifting scenario. There are those who fear that artificial intelligence will supplant us, taking our jobs and living beyond the writ of human laws. Others regard such scenarios as too futuristic to be worth fretting over. But the disagreements are about the rate of travel, not the direction. Few doubt that machines will one day surpass more of our distinctively human capabilities. It may take centuries but, compared to the aeons of evolution that led to humanity’s emergence, even that is a mere bat of the eye. This is not a fatalistic projection. It is cause for optimism. The civilisation that supplants us could accomplish unimaginable advances — feats, perhaps, that we cannot even understand.

Human brains, which have changed little since our ancestors roamed the African savannah, have allowed us to penetrate the secrets of the quantum and the cosmos. But there is no reason to think that our comprehension is matched to an understanding of all the important features of reality. Some day we may hit the buffers. There are chemical and metabolic limits to the size and power of “wet” organic brains.

Today’s computers do not learn like we do. Their internal network is far simpler than a human brain, but they partly make up for this disadvantage because their “nerves” transmit messages at the speed of light, millions of times faster than the chemical transmission in human brains. They can learn to identify dogs, cats and human faces by crunching through millions of images. They learn to translate from foreign languages by reading multilingual versions of millions of pages of EU rules, among other documents (and, crucially, they never get bored).

These are primitive steps, and there is disagreement about the route towards machines of human-level intelligence. Some think we should emulate nature, and reverse-engineer the human brain. Others say that is as misguided as designing flying machine by copying how birds flap their wings. Philosophers debate whether “consciousness” is special to the wet, organic brains of humans, apes and dogs, so that robots, even if their intellects seem superhuman, will still lack self-awareness or inner life. But of the kind of “thinking” that has enabled humans to understand and then harness the forces of nature, far more will be done by silicon computers (or quantum ones) than has ever been managed by people.

Artificial minds will not be confined to the 14 mile layer of water, air and rock in which organic life has evolved at the earth’s surface. Indeed this biosphere may be far from an optimal habitat for post-human “life”. Interplanetary and interstellar space will be the preferred arena for the grand constructions of robotic fabricators, including the non-biological brains that might one day develop insights as far beyond our imaginings as string theory is for a monkey.

The collective activities of human brains have underpinned the emergence of all our culture and science. They may not have been the first intelligences in the cosmos, however, and they are most unlikely to be the last. Searches for extraterrestrial intelligence are attracting growing support. Astronomers have learnt in the past decade that there are likely to be billions of earthlike planets, orbiting stars in our galaxy. Searches will focus on the nearest of these. But we do not know how likely it is that chemistry generates life (replicating, metabolising, entities), nor what chance primitive organisms have of evolving to earth-like biospheres. If our searches fail, there will be a compensation: if advanced life is exceedingly rare, we need be less cosmically modest. Our earth, though a tiny speck in the cosmos, could be the unique “seed” from which intelligence spreads through the galaxy.

Our era of organic intelligence is a triumph of complexity over entropy, but a transient one, which will be followed by a vastly longer period of inorganic intelligences less constrained by their environment. If life is widespread, worlds orbiting stars older than the sun could have had a head-start. If so, aliens are likely long ago to have transitioned beyond the organic stage.

We have no crystal ball. But it is a fair bet that machines, not organic brains, will most fully understand the cosmos. They may be our own remote descendants. Or they may be out there already, orbiting distant stars. Either way, it will be the actions of autonomous machines that will most drastically change the world, and perhaps what lies beyond.

The writer is the Astronomer Royal