At a lively conference held near Harvard University on May 1st and 2nd, ten distinguished speakers addressed a fascinated crowd on “The Future of Human Life in the Universe.” Interstellar travel, the search for life in the galaxy, the menace of various cataclysms, the past evolution of life, humankind’s control of its own evolution — everything was on the table.
Each talk lasted only 30 minutes but unleashed a barrage of questions from the audience that had to be cut after 25 minutes. The friendly atmosphere of the venue — the independent Zero Arrow Theater in Cambridge, Massachusetts — contributed to the exchanges, as the speakers were practically in the audience. Part of the Cambridge Science Festival, the conference was organized by the Harvard-Smithsonian Center for Astrophysics and the Harvard Origins of Life Initiative.
Andrew Knoll, a professor of natural history and planetary sciences at Harvard, placed humankind and intelligence in the context of the biological world, reminding us that most life on Earth is microbial.
“There may be many intelligent species out there, but that doesn’t help us communicate with them,” observed Gerrit Verschuur, one of the first radio astronomers to search for alien signals. Now a physics professor at the University of Memphis, Verschuur believes that our development of electronic technology was accidental, a consequence of the discovery of amber (fossilized resin that can be rubbed to produce static electricity) and lodestone (magnetic rocks) three millennia ago.
Verschuur discussed the famous Drake equation for estimating how many technologically advanced civilizations inhabit planets in our galaxy. After plugging in some numbers, he explained that we had to accept the fact that the closest such civilization may live at least 2,500 light-years away: “We’re not going there anytime soon.”
Indeed, Mars and the asteroids are about as far as we can plan on traveling now. Even with the most fuel-intensive options, Mars would require a round trip of at least 8 months plus the duration of stay, explained Maria Zuber, geophysicist at MIT. And Zuber noted that of 47 missions sent to Mars, only 19 “got there and did anything whatsoever.” She added that this success rate was on par with Ted Williams’s 1941 batting average of .406.
“Science will never be the driver to send humans to Mars,” Zuber continued, explaining that robots can explore much more cheaply. But she justified sending people to Mars: “If they’re sent, they’ll find extra stuff.” Cosmic radiation, however, is turning out to be a serious problem. Humans on Mars could shelter from it under Martian soil or in a lava-tube cavern, but they would still need protection during the flight. Nevertheless Zuber was confident that “the technology can all be solved.” She noted that Mars has scary dust storms but a lot of accessible water ice. And unlike on Earth, the low gravity would make running more efficient than walking.
Dimitar Sasselov, an astronomer at Harvard, emphasized the possibility that super-Earths, planets with masses of 2 to 10 Earths, may be ideally suited to life. Sasselov expects some of these planets to be rocky as well as having water and an atmosphere. In addition, being a larger gyroscope might make a super-Earth's axis and climate stable enough for life to evolve smoothly without the stabilizing action of a big moon. The smallest such planet known, Gliese 581e, was discovered last month, weighing in at about twice the mass of the Earth. But it’s too close to its parent star to be habitable.
David Charbonneau, a planet-hunter at Harvard, explained that the best prospects for finding smaller, actual exo-Earths is to watch dim red-dwarf stars (spectral class M.) “When I grew up, I was told the Sun was an average star,” he said, but M dwarfs are in fact more numerous and longer-lived. Being both small and low-mass, they make small planets easier to find by either the transit method or the gravitational-wobble method. And their habitable zones are so close-in that any good Earths would be close enough to the star to have a reasonable chance of transiting it.
But complex life may be rare, said paleontologist Peter D. Ward of the University of Washington. Ward co-authored the 2000 book Rare Earth, but he clarified that “rare doesn’t mean unique.” Earth is not so kind to life, Ward said, contrary to the Gaia hypothesis of James Lovelock. Ward stressed that asteroid impacts do not match the times of mass extinctions. Maybe the cause of the extinctions, he offered, is that “life blunders.”
The way this happens, he proposed, is by “microbes which didn’t understand their Gaian job; which screwed up” and produced too much noxious hydrogen sulfide. This would happen after spells of high atmospheric carbon dioxide cause severe global warming, homogenizing ocean temperatures and halting global marine currents that distribute oxygen underwater. Most ocean life would die, but anoxic bacteria would thrive in these conditions. “This can cause a mass extinction, and it’s entirely life-driven,” Ward said. He called his idea the “Medea hypothesis,” contrasting the benevolent Gaia to Medea, “the worst mother in history.”
Beyond the dangers of global warming, nasty bacteria, and asteroid impacts, Ward discussed the end of life on Earth in the really long term. In about a billion years the oceans will finally boil away as the Sun evolves and heats up. He also noted an irony: By increasing the carbon dioxide in the atmosphere now, humans are doing a good thing too early and too quickly. In some hundreds of millions of years, lack of carbon dioxide will become an issue for all plant life, as organisms gradually it out of the atmosphere and stash it in rock formations.
Ward urged that we spread beyond Earth: “We cannot keep our eggs in this very fragile basket.” But he ended with a positive note: “My model now is, ‘Better living through engineering’.”
For any one species such as humans, the “long-term future” means much, much sooner than hundreds of millions of years, however. A typical species in nature lasts just a few million years, and in our own case, said genomic researcher J. Craig Venter, “we can potentially accelerate the evolutionary process by six orders of magnitude.”
Venter gave an update of the progress in synthetic genomics. “We have not yet booted up the synthetic chromosome,” Venter said, but it’s coming. He pictured a future in which “we wouldn’t have to eat anymore, we could just photosynthesize.” To ward off concerns of mutations going awry as in the case of the flu virus, “we’re trying to limit the ability to self-evolve,” Venter said. “We don’t necessarily want our plants to walk.”
This discussion raised questions about separate future evolution of humans on Earth and in space. If evolution is drastically accelerated and humanity also spreads out, it may quickly diversify into new species along very different lines.
Biotech businessman Juan Enriquez brought the question home. If our species can control its evolution, we face options. Some people would want to stop evolution, on the grounds that remaining “human” means remaining the way we are. Others will want to use this power to evolve faster (as advocated by the transhumanist movement). Enriquez coined the name Homo evolutis for this more adventurous branch.
“I don’t believe life is mostly on planets,” said physicist and mathematician Freeman Dyson of Princeton, bringing an unconventional ending to the conference. Dyson thinks “we’re not clever enough to guess what Medea did, or Gaia, whoever it was,” so he urged that we “look for what’s detectable, not what’s probable.”
For instance, Dyson discussed kelp-like life forms in the ocean inside Europa (an icy satellite of Jupiter) perhaps creeping up to the vacuum of the surface to collect sunlight. A camera on a spaceship between Europa and the Sun, Dyson said, might spot reflective light receptors on them the way hunters spot animals at night by shining lights at their eyes. Dyson also noted that if life evolves without an atmosphere, it will have a much easier time spreading through the universe. Such organisms on Kuiper Belt objects might need so much light-collecting area that far from the Sun that they would cover the entire surface and be visible now.
Dyson commented, “On none of the stuff I have been pontificating on am I an expert.”
Nor, at this point, is anyone. There’s only one thing we know for sure about the future — that it’s coming.
Johannes Hirn studies science and medical journalism at Boston University, and is currently interning at Sky & Telescope.