Science fiction's crystal ball has made the future of human evolution look like a wild ride: Brains are inflated, ears stretched, hard drives somehow installed where our hearts should be.
But enough of science fiction -- what about the real thing? Is the human race on the cusp of developing an extra pair of eyes? Ten-foot-long legs? A resistance to the common cold?
Dr. Donald Johanson, director of the Institute of Human Origins, says the forecast is much less dramatic that Hollywood would have us believe -- and before we can even entertain what we might look like in 100,000 years, we need to first worry about lasting that long. And that's hardly a given, he says.
Johanson, who founded the institute, should know what he's talking about when it comes to evolution. In 1974, he discovered the fossilized remains of one of our species' most famous ancestors, a 3.2-million-year-old female Australopithecus Afarensis -- better known as "Lucy." He spent the next three decades scripting prehistory.
Through his exhaustive studies of the past, he has a unique perspective on where our future lies.
"We were crafted very intimately by our interaction with the natural world," Johanson said. "I think if we look at the past for some clues to what might happen in the future, we're stimulated to think that if the earth has been without major human influence for hundreds of millions of years, billions probably, and we are now as a species so dramatically influencing the environment, who knows what the outcome is going to be when we do dramatically change the environment?"
During the Industrial Revolution, technology transformed the idea of evolution for good, slowing -- maybe even stopping -- its physical manifestations and redefining it as a cultural phenomenon. Instead of our bodies changing in the face of challenges, we used our minds to circumvent any shortcomings.
That obviously wasn't the case so much in Lucy's era. But her species managed to get by: It lasted from 3.9 million to 3 million years ago by growing with its surroundings. We'd have to last another 9,000 centuries to match it.
"We tend very much to be ego-centricus because we think that as Homo Sapiens we don't have much to worry about and our species will continue to survive forever," Johanson said. "Yet when you look at lessons of the past, Lucy's species walked on the earth for a million years, roughly. Now I don't know how you measure success, but that's a pretty successful tenure on this planet."
Our genus eventually left Lucy in the dust as hominids developed into carnivores around 2.6 million years ago. Unlike our ape-like ancestors, we're unlikely to develop much further physically, Johanson argued -- we simply don't need to.
He summed up our situation using a scene from the film "The Day After Tomorrow," when the northern half of the country rapidly (and unrealistically, he said) succumbs to an ice age.
"As a cultural animal you wouldn't grow hair on your body in that situation," Johanson said. "You'd do what they did in that library: burn wood and try to stay warm. We filter everything through culture today and our own specific adaptations I don't think are going to change very much."
That means no big heads, no webbed feet, no giant eyes. That is, if we leave it to nature. The Human Genome Project has put humans in a position where we could theoretically alter the germ line and erase undesirable traits like Down's Syndrome before birth. But Johanson isn't comfortable making guesses when it comes to tinkering with the genome.
"You might develop people who are super human but are sterile, for example," Johanson said. "We don't know the outcome of many of these manipulations. That's one of the greatest reservations that most biologists have, getting in and tinkering with the genome. It has already been balanced to work at its optimum level now."
Our future as a species also depends on another delicate balance -- between human civilization and the natural world. Should this year's hurricanes, earthquakes and mudslides be sending us a message about what's on tap for humans?
"I'm hopeful that some of the crises that we see around the world today are the sorts of things that will get us to think about the fact that we are part of the process of the living world," Johanson said. "I think that for the future we as a species need to be very cognizant of being a part of the natural world, a product, and if that is to be the case we need to reinvent a reverence for the natural world."