The Next Species: The Future of Evolution in the Aftermath of Man (32 page)

The European Space Agency, the National Space Biomedical Research Institute (in Houston, Texas), and the Russian Federal Space Agency recently completed a 520-day experiment locking six “marsonauts” in a simulated spaceship near Moscow. Five hundred and twenty days is about what it would take for a round-trip flight to
Mars, with about thirty days to explore the surface. During the entire simulation, the crew went without sunlight, fresh air, or fresh food.

There were significant human problems to work through. With regard to rest, there were no external cues, such as sundown, to let the astronauts know when it was time to sleep. They had to rely on artificial cues like watches and other astronauts waking them up. Without gravity, the body had trouble telling what was up and what was down. In space, the natural orientation of the body is taken away, particularly for arms and legs. On Earth, vision, hearing, and touch combine to tell you where you are. You feel the floor under your feet, the chair that you sit upon. But weightlessness takes away those feelings, and the senses send confusing signals to the brain, which results in motion sickness.

The big thing, however, was the effect to bodily organs, particularly the cardiovascular system. While in space, the body no longer feels the downward pull of gravity that distributes the blood and body fluids to the lower extremities. Fluids start to accumulate in the upper body, away from the legs and feet. In space, astronauts actually start to look different as their faces puff out from the additional fluid in their upper bodies.
They develop bird legs as the circumference of their legs shrinks due to decreased fluid in the lower body.

The heart has less work to do because it takes less energy to float around a spacecraft than it would to walk or run around planet Earth. Bones lose calcium, making them weaker, and the muscles atrophy because gravity is not providing the normal resistance to movement. Exercise machines aboard the flight can mitigate some of these effects, but that doesn’t eliminate all the aftereffects. Most Russian cosmonauts, after spending months in space, were carried away from the spacecraft on special stretchers. At their homecoming receptions, climbing the podium was often too challenging so soon after reentering Earth’s gravity.

Interplanetary travel would be a major evolutionary force for Earth-born settlers on Mars, and frequent travel between Earth and Mars would be unlikely because of the expense. Living on Mars could
produce long-term biological changes that would make a return to Earth ultimately impossible. With isolation a natural part of the job, the gradual push of evolution toward becoming another species could happen in outer space just as well as here on Earth.

Gravity wouldn’t be the only selective force. Others would include breathing compressed air and adjusting to different loads of UV radiation. The need to eat, go to the bathroom, have sex, give birth—all these vital functions would be seriously altered by changes in gravity, air, and radiation.

But even though such a change would be an interesting step in the evolution of man, it doesn’t answer the primary question of life on Mars.
Is it someplace where large portions of our population might escape if we mess things up down here?

There are so many things that could go wrong, one of which is that the reality TV show on Mars gets canceled due to lack of an audience and the venture runs out of cash. And there are other “little” things, like what happened with Biosphere 2’s oxygen, which wasn’t expected. Biosphere 2’s soil was rich in organic material that was taken up by microbes, which used up oxygen and created a lot of CO
₂
. The plants in the facility should have been able to process the CO
₂
and produce more oxygen, but it was later determined that calcium hydroxide in the concrete was removing the CO
₂
and not releasing oxygen. No one would have imagined that the concrete in Biosphere 2 might eventually suffocate the residents.

After Mars, the next likely place for life in our solar system is the moons of Jupiter. That planet has four large moons and at least forty-six smaller ones. Io, for example, is the most volcanically active body orbiting Jupiter. Io’s surface is covered by sulfur in different colorful forms, and its volcanoes are driven by hot silicate magma. One could keep warm next to an Io volcano, but it would be hard to get insurance. Europa’s surface is mostly water ice. It may be covering an ocean of water or slushy ice beneath. This would create a “habitable zone” for microbes but it wouldn’t be a place where you would want to spend your vacation, let alone the rest of your life.

Scientists are currently looking for
habitable planets like Earth around other stars in our solar system, and they’ve found numerous prospects. But the closest star in our solar system, Alpha Centauri B, is about 4.37 light-years away from our sun. One light-year is about 6 trillion miles (10 trillion kilometers), which means Alpha Centauri B is about 26 trillion miles (41.5 trillion kilometers) from our sun. NASA’s
Kepler
planet-finding spacecraft has found Earth-like planets around distant stars, only they’re 275 times more distant.

Interstellar travel could happen one day in the distant future, but it’s just as likely that mankind will have exhausted Earth’s natural resources and made the planet unlivable before then. Right now mankind seems uninterested in either goal. What’s the chance that evolution could provide the world with another species that could outcompete us and change the course of human history?

M
ANY SCIENTISTS
hold the belief that natural evolution stopped for
Homo sapiens
about forty thousand to fifty thousand years ago in Europe. That’s when man began to chart his own destiny apart from nature. Human inventions like sewing needles provided warm clothes to protect against the cold as opposed to natural selection providing more hair. Man began to think in symbols, which morphed into words, and this expanded into complex language. And language provided the key to elaborate cooperation.

This wasn’t just hoots and loud calls with others in a group for the purpose of bringing down an animal. Language was useful for establishing trade that could reach across vast distances, relaying experiences across large chunks of time, and learning where the best food was and how to get it.

Man began to utilize an ever more complex set of tools: spears, spear throwers, bows and arrows. He grew leaner. He didn’t need large muscles and thick bones to kill game at close range—he killed from a distance. The new weapons rewarded those with a better throwing arm and a better aim. The atlatl (spear thrower) and the bow allowed modern humans to
kill large animals without having to have large
muscles. Thus, humans could run faster, cover more ground, and not have to eat as much.

With the invention of nets, harpoons, and hooks, humans began to fish. It was less dangerous and required less physical effort. One could now eat meat, fish, and berries—a broad-based diet that gave man the advantage in a world that was then in the middle of an ice age. The use of fire and pottery for cooking made large teeth less vital and man’s jaw and teeth began to recede. Cultural innovation began to affect evolution.

Yet Stephen Jay Gould, the late Harvard paleontologist, looked at all this and hesitated to give it an evolutionary consequence. Gould thought that fifty thousand to one hundred thousand years was but the blink of an eye in evolutionary development and far too rapid to see any significant evolutionary changes. But Gregory Cochran and Henry Harpending, anthropologists at the University of Utah, in Salt Lake City, say there has actually been an increase in genetic change in modern man in the last ten thousand years. In their book
The 10,000 Year Explosion: How Civilization Accelerated Human Evolution
, they propose that not only has human evolution not stopped, it has accelerated. Their belief is that evolution is now happening about
one hundred times faster than the long-term average of our species’ existence. Could that lead to a new species?

To arrive at this figure, Harpending and Cochran analyzed data from the International HapMap Project, an effort to describe the common patterns of genetic variation in the human genome with a goal of uncovering the genetic roots of complex diseases. The project gathered results from eleven different populations around the world, spotlighting evidence from specific sites in the human genome that influenced gene expression.

“We can compute the average amount of change in the human genome and it’s one hundred times faster,” says Harpending. “Which make sense. There’s one hundred times as many people, and that creates one hundred times as many targets for genetic mutations.”

As genes develop, so do mutations, which are genes that don’t look or act as they did before. Most of these mutations are discarded in favor of the standard set, but once in a while a favorable genetic mutation occurs, with the result that people with the mutation have more children, are better adapted to fight off disease, or simply live longer. Such mutations offer an advantage: their owners do better and are more likely to survive. When this happens, the mutation is selected for and is passed on to future generations. Harpending and Cochran looked for these types of favored mutations in the human genome in regions of unshuffled genes, which indicate recent selection, since nature regularly reshuffles its genes.

These favorable genetic mutations have helped man in different ways. Man living at higher altitudes had to adapt to less oxygen in the air. To accomplish this, Andeans developed barrel chests and blood that held more oxygen, while Tibetans developed faster breathing to take in more oxygen. Scientists from the Beijing Genomics Institute recently found a set of genes in Tibetans that have helped them adapt to low oxygen levels. These “new” genes were only three thousand years old.

Harpending and Cochran also found that 7 percent of human genes underwent evolution as recently as five thousand years ago. And a lot can happen in five thousand years. Darwin chose domestic animals to illustrate much of his
On the Origin of Species.
Dogs come in enormously varied shapes and sizes. Take, for instance, a Chihuahua, which averages 7 pounds (3.2 kilograms), and a Great Dane, which averages 115 pounds (53 kilograms). Both come from the same ancestor.
Neither of them looks like a wolf, yet most breeds of dog were derived from wolves in the last two hundred years.

Man is also changing. The last ten thousand years have seen numerous genetic changes to human bones and teeth along with the rapid evolution of our diet and our adaptions to disease. We are taller. Our life expectancy is much greater. Changes in society have led to evolutionary adaptations. Harpending says that we are getting less alike, so that we are not merging into a single mainstream
human type. We are not the same humans we were one thousand or two thousand years ago. This may account for part of the
differences between the Viking invaders and their peaceful Swedish descendants.

Harpending’s coauthor, Cochran, says: “History looks more and more like a science fiction novel in which mutants repeatedly arose and displaced normal humans—sometimes quietly, by surviving starvation better, sometimes as a conquering horde. And we are those mutants.”

As
Homo sapiens
migrated into Eurasia, evolution produced changes in skin color and adaptations to cold. Some of the biggest changes came with the transition to agriculture. Larger populations and more dense living conditions promoted virulent epidemic diseases like cholera, typhus, yellow fever, malaria, and smallpox. But over time this led to the development of some genetic resistance to those diseases.

Neanderthals, a species that developed in Europe, had adaptations to climate that other
Homo
species never developed in Africa. As we have discussed, resistance to such diseases as malaria is far more prevalent in Central Africans than Northern Europeans. Skin color is another important adaption to environment. Monkeys and other primates have pale skins under their fur, but humans that lost their fur, perhaps to sweat more freely, evolved darker skins to protect against ultraviolet light. The process reversed itself when man first ventured northward, where his skin grew lighter, maybe to better synthesize vitamin D.

Peter Grant at Princeton University worked on the Galápagos Islands and likes to lecture his students about the persistence of evolution, claiming that evolution is always happening. Genes of this generation are not the same as the last. Nor will they be the same in the next. He claims it’s a mathematical certainty. Genes keep changing. You may not notice it. The trees around you may look the same. And the birds and the squirrels may look similar year after year. “They aren’t,” Grant said in an interview with author Jonathan Weiner for
The Beak of the Finch: A Story of Evolution in Our Time
. “
They’re different. But you can’t see it, the differences are too subtle.”

Evolutionary changes are proceeding at a genetic level, and sometimes they are heritable and apparent—the difference in height and longevity between you and your grandparents—but most times they are not.

One of the most
game-changing mutations to the human genome was lactose tolerance. It enabled man to digest milk beyond infancy. It is responsible for the largest human expansion in history, that of the Indo-European language family.

The term “Indo-European” refers to the family of related languages that spread over western Eurasia, the Americas, and Australia. It includes Spanish, English, Hindi, Portuguese, Russian, German, Marathi, French, and numerous other languages and dialects. Today there are over three billion native speakers, close to half the human population on earth.

The idea of a single large linguistic family first arose from similar observations of people from England and people from India. Sir William Jones, the chief justice of India, mentioned these similarities in a lecture in 1786, and scholars began to trace its history through linguistics and archaeology. The first or Proto-Indo-Europeans raised cattle, sheep, and goats. They were warriors, the young men gathering into brotherhoods with challenging initiation rites.