The potential of advanced AI, and concerns about it downsides, are rising on the agenda—and rightly. Many of us think that the AI field, like synthetic biotech, already needs guidelines that promote "responsible innovation"; others regard the most-discussed scenarios as too futuristic to be worth worrying about.
But the divergence of view is basically about the timescale—assessments differ with regard to the rate of travel, not the direction of travel. Few doubt that machines will surpass more and more of our distinctively human capabilities—or enhance them via cyborg technology. 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. That's why, in a long-term evolutionary perspective, humans and all they've thought will be just a transient and primitive precursor of the deeper cogitations of a machine-dominated culture extending into the far future, and spreading far beyond our Earth.
We're now witnessing the early stages of this transition. It's not hard to envisage a "hyper computer" achieving oracular powers that could offer its controller dominance of international finance and strategy—this seems only a quantitative (not qualitative) step beyond what "quant" hedge funds do today. Sensor technologies still lag behind human capacities. But when robots can observe and interpret their environment as adeptly as we do they would truly be perceived as intelligent beings, to which (or to whom) we can relate, at least in some respects, as we to other people. We'd have no more reason to disparage them as zombies than to regard other people in that way.
Their greater processing speed may give robots an advantage over us. But will they remain docile rather than "going rogue"? And what if a hyper-computer developed a mind of its own? If it could infiltrate the Internet—and the Internet of things—it could manipulate the rest of the world. It may have goals utterly orthogonal to human wishes—or even treat humans as an encumbrance. Or (to be more optimistic) humans may transcend biology by merging with computers, maybe subsuming their individuality into a common consciousness. In old-style spiritualist parlance, they would "go over to the other side."
The horizons of technological forecasting rarely extend even a few centuries into the future—and some predict transformational changes within a few decades. But the Earth has billions of years ahead of it, and the cosmos a longer (perhaps infinite) future. So what about the posthuman era—stretching billions of years ahead?
There are chemical and metabolic limits to the size and processing power of "wet" organic brains. Maybe we're close to these already. 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.
So, 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. Moreover, the Earth's biosphere in which organic life has symbiotically evolved, is not a constraint for advanced AI. Indeed it is far from optimal—interplanetary and interstellar space will be the preferred arena where robotic fabricators will have the grandest scope for construction, and where non-biological "brains" may develop insights as far beyond our imaginings as string theory is for a mouse.
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. Moreover, evolution on other worlds orbiting stars older than the Sun could have had a head start. If so, then aliens are likely to have long ago transitioned beyond the organic stage.
So it won't be the minds of humans, but those of machines, that will most fully understand the world—and it will be the actions of autonomous machines that will most drastically change the world, and perhaps what lies beyond.