Jan. 31, 2002
by Seth Shostak – Senior Astronomer
What does it mean to be intelligent? I get this question a lot, given the fact that “intelligence” is the last word of the SETI acronym. “Is there intelligence on Earth?” wags will ask (and by so doing, make their query relevant). What defines a species as intelligent, and how do SETI researchers decide?
SETI folk are mostly interested in alien intelligence, not the brainpower of the local school kids. But investigating terrestrial IQs may help us estimate how often sentient beings evolve elsewhere. To test human intelligence is straightforward, if controversial. But how can we assess the brainpower of other critters? One approach taken by biologists is to compute an “encephalization quotient,” which is really no more than a measure of how weighty the brain is for an animal of a given body size. Of course, bigger bodies usually mean bigger brains (compare at least in your mind, if not the kitchen the brain of a rhino to that of a mouse). But sheer size isnt the whole story. Animals of any given mass have a variety of brain weights. Those with the heftier cerebrums are observed to have more sophisticated behavior, and are ranked as smarter. Humans, it will not surprise you to learn, have the largest brains for their body mass, roughly twice that of their nearest intellectual competitors, the chimps. That factor-of-two difference determines who runs the planet.
This is all interesting for studying the evolution of sentience, but in practice SETI has a far simpler definition of what it means to be intelligent: youre “intelligent” if you can build a powerful laser or a thumping radio transmitter. After all, thats what we demand if our SETI experiments are going to find something. In other words, the “intelligence” in SETI really means technical sophistication. By that very practical, operational definition, humans have been intelligent for less than a century.
In other words, when it comes to the type of intelligence that counts at least for interstellar signaling were new kids on the galactic block.
What about the other kids? How technically advanced will the aliens be? Keep in mind that the Galaxy has been around for many billions of years longer than the Earth. If extraterrestrials are plentiful, then we can expect them to be in all stages of development. But of course we wont pick up signals from any that are less advanced than we are. Aliens that SETI can find will be at least as scientifically competent as folks here on Earth.
But would they be at about our level? After all, in the movies, they often are. The answer depends on only one thing: how long technological civilizations last. No one knows the lifetime of sophisticated societies, a fact that weve discussed in these columns before. Pessimists assume that within a few centuries, technological societies inevitably blow themselves and their transmitters to smithereens. Optimists suspect that the possibilities for a scientifically literate society will open the door to long-term survival: perhaps millions of years or more.
Frank Drake has estimated the average lifetime of technologically adept civilizations at 10 thousand years. This is not overly optimistic. After all, Homo sapiens has been around for 300,000 years, so another 10 thousand isnt much. Indeed, its a bit of a downer to think that once technology gains a foothold we are near the end of our ride.
But suppose Drake is right. Then humans are in the bottom 1 percent of technological advancement, no matter how many civilizations are out there. We are among the new kids on the block, and if the number of alien societies is small or the average lifetime is larger, then we could easily be the newest kid.
Technological progress on Earth, at least recently, has been very fast. Indeed, the growth in computer power one measure of our prowess has been exponential. If this is a general phenomenon for intelligent societies, then we are incredibly primitive in comparison to more than 99% of the civilizations we could detect.
Is there intelligent life on Earth? By our standards, maybe. But by theirs, we are probably as dumb as doorknobs. I, for one, hope to develop a little humility.
Related articles
