Where Did We Come From? Series

According to Hollywood, there’s no shortage of alien life in the universe. Unfortunately, these aliens are usually presented as hostile to humanity. In fact, flicks like War of the Worlds, Invasion of the Body Snatchers, and Independence Day depict cosmic creatures that threaten humanity’s very existence.

On the other hand, throughout history some thinkers, philosophers, and even scientists have taken a completely different spin on the question of the relationship between life on Earth and life in outer space. Instead of imagining aliens as hostile, even seeking to wipe out humanity, they believe that alien life could have been what seeded life here to begin with. Thus, far from being hostile, alien life would be quite friendly to us.

What’s behind this theory, and is there anything to it?

Seeds from space

The idea that life on Earth originated from outer space is called panspermia—from the Greek words pan, which means “all,” and spermia, which means “seed.” It’s basically the theory that not only does alien life exist, but it can spread throughout the cosmos and seed other worlds. This seeding can happen through microbes in asteroids or other cosmic debris that lands on planets and fortuitously gets life going there. Or, as some have argued, perhaps aliens came to our planet purposely and started life here— and who knows on how many other worlds as well.

One of the twentieth century’s most famous scientists, Francis Crick (who with James Watson discovered the DNA double helix molecule), proposed just such an idea, which he called directed panspermia. Though a militant atheist, Crick argued that life on Earth was just too complicated to have formed by mere chance. “An honest man,” he said, “armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have had to be satisfied to get it going.”

Hence, he proposed a solution: life itself was first brought to Earth in spaceships billions of years ago by more highly evolved creatures. “As an alternative to these nineteenth-century mechanisms,” he wrote, “we have considered Directed Panspermia, the theory that organisms were deliberately transmitted to the earth by intelligent beings on another planet.”

Thus, one of the last century’s greatest scientific minds argues that, perhaps, aliens in spaceships first brought life to Earth, and that explains how we all got here.

Cosmic solution to a very earthly problem

Others, who think there could be something to the panspermia idea but reject the directed part, believe that alien life could have been transported through space by comets or asteroids or meteorites—but by accident. After some sort of interplanetary collision or explosion, microbes hitchhiked rides on the debris left over from the collision. This is called ballistic panspermia. Then, managing to survive the rigors of space, these microbes were hurled across the cosmos until they landed on other planets, including ours.

Hence, they were the seeds that by chance happened to take root, survive, multiply, and evolve into what we see today. Therefore, according to this theory, everything from fungus to turnips to the Boston Symphony Orchestra had their origins in microbes from other planets.

Even proponents of panspermia will admit that their theory is highly speculative. But it would solve what many evolutionary biologists still consider the most troublesome problem of their theory: the explanation of the origin of life on Earth. How could the first life-form on our planet have arisen from nonliving material, as the evolutionary theory teaches? This question remains unanswered. The panspermia idea (whether directed or ballistic or any other version), if true, would in one fell swoop give a cosmic solution to what has been a very earthly problem.

Allan Hills 84001

Some scientists have claimed that we already have evidence for alien microbes reaching Earth. In 1996, headlines were splashed around the world that a meteorite found in Antarctica a decade earlier, called the Allan Hills 84001, had shown evidence of life from Mars. The theory stated that the rock was blown off the Martian surface by a meteorite impact 4.5 billion years ago and landed on our world billions of years later. The announcement of the possible discovery of what would have been extraterrestrial life caused quite an international stir, even prompting then United States President Bill Clinton to make a televised announcement to mark the event.

However, critics quickly pointed to many problems with that specific interpretation of the evidence found in the meteorite. Before long, papers had been written arguing that the strange features on the rock were mere leftovers of unique geochemistry and that nothing on the meteorite showed microbiological features. To this day scientists debate the question, even if the consensus is that Allan Hills 84001, however interesting, didn’t carry evidence of extraterrestrial life from Mars.