Did Humans Move To Earth From Another Planet? | Unveiled

Did Humans Move to Earth from Another Planet?

For billions of years, Earth has been an ideal home for organic life. A myriad of life forms have evolved here, from the creatures that crawled out of the oceans’ primordial soup, to the dinosaurs, to we humans. But what if that’s not the whole story?

This is Unveiled, and today we’re answering the extraordinary question: did humans move to Earth from another planet?

How did life first arise on our planet? One popular answer to this question is the theory of panspermia. Panspermia suggests that life on Earth is not unique, and that the necessary materials travel between planets and star systems inside dust, asteroids, meteors, and other forms of cosmic debris. These materials aren’t thought to consist of complex, multicellular organisms, but of microbial life and the elements common to it: carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. Most of these elements are key ingredients in amino acids, which have been discovered in meteorites, providing slim support for the theory.

But while panspermia is technically possible, these few meteorites are all the evidence we have, and they’re not actually that promising. The amino acids contained within them are new and exciting but don’t contain full proteins. Whether or not we’ve found any trace of actual microbial life inside a meteorite remains hotly debated. And importantly for our topic, life arriving on Earth via panspermia isn’t the same as conscious, sentient aliens deciding to up sticks and move here. The microbes in panspermia lack any agency whatsoever; arriving at a habitable world would be a complete coincidence.

Given the number of potentially habitable planets in the universe, it’s highly likely that there’s extraterrestrial life out there. The odds for intelligent life are lower, but it’s hard to imagine that we’re the only sentient beings around. Supposing that there are extraterrestrials capable of space travel in our galaxy, it’s not impossible that Earth has had visitors from outside of our solar system. Then again, the conditions of the planets within our solar system were once very different. So, any such visitors could also have come from neighbouring planets. It’s all purely hypothetical, but let’s look at the possibilities.

If aliens did travel to Earth in a spaceship billions of years ago, and eventually evolve into human beings, which planets might they have originally called home?

Well, the other inner planets are promising. All three – Mercury, Venus, and Mars – may have once been habitable. Yes, even though Mercury is the nearest planet to the sun and can reach scorching daytime temperatures of 800 degrees Fahrenheit, it actually has icy poles. This is because the poles are in perpetual darkness, meaning that Mercury’s polar regions could have hosted life the way Earth’s non-extreme regions do today. But Mercury does have disadvantages where intelligent life is concerned; its poles and subsurface regions could have supported microbial life, but this microbial life wouldn’t have been able to build a spaceship and come to Earth - which makes Mercury an improbable source for humanity.

So, what about Venus? Nicknamed “Earth’s evil twin”, Venus is one of the most wildly inhospitable places in the solar system, with surface temperatures of up to 863 degrees - exceeding those of Mercury, despite being further from the sun. The reason for this is that Venus’s atmosphere is full to bursting with carbon dioxide, which is so dense that Venus’s atmosphere is over 90 times heavier than Earth’s! It’s the equivalent of being 3000 feet underwater; and above you are clouds raining sulfuric acid.

But Venus wasn’t always like this. In fact, it may have been habitable and Earth-like for billions of years. Eventually, however, the release of carbon dioxide from the planet led to a runaway greenhouse effect, which altered conditions drastically. This could have been accelerated by changes to Jupiter’s orbit pushing Venus nearer to the sun. But this wouldn’t have been an instantaneous transformation. There could feasibly have been time for intelligent aliens to build a spaceship to escape their doomed planet and head towards Earth. Considering the proximity of Earth from Venus, the blue planet could have been an ideal candidate. And as we all know, it’s more than capable of sustaining an abundance of life.

Since Venus’s surface is completely obscured with clouds, only very few space probes we’ve sent to the surface have been able to see anything. So there could, in theory, be relics of an ancient civilization that remain invisible to us here.

The same isn’t true of Mars. Like Venus, Mars is close to Earth and may have been habitable billions of years ago. And like Mercury, it has ice as its poles. But due to its lack of atmosphere, we’ve managed to map its surface in extreme detail. There definitely aren’t any large alien ruins on Mars’s surface – if there were, we definitely would have found them by now. However, there could be underground ruins we know nothing about. And in fact, with Mars’s plummeting temperatures as it shed its atmosphere maybe life underground would have fared better. Just like Venus, Mars would have become uninhabitable slowly. An advanced species would have been able to work this out and make the decision to leave, presumably heading to Earth as the best destination. But we’ll have to wait until we further explore Mars to know if there’s any truth to this theory.

But the inner planets aren’t the only bodies that could have hosted intelligent life that eventually made its way to Earth. While it’s possible that bizarre alien lifeforms evolved and live within gas giants themselves, any creature like this wouldn’t be fit to live in Earth’s atmosphere. We should instead look at the moons of those gas giants.

Jupiter and Saturn both boast moons that have a lot of promise. Jupiter has Europa while Saturn has Titan and Enceladus. Scientists believe that both Europa and Enceladus have vast subsurface oceans. The ocean inside Enecaladus sometimes spews out enormous geysers of water so high that they leave the moon’s atmosphere. While intelligent life probably couldn’t have travelled to another planet this way, it could have led to panspermia, with ice from Enceladus migrating through the solar system.

Titan is even more exciting; it’s the most Earth-like body in the solar system aside from Earth itself, with an atmosphere and hydrocarbon lakes on the surface. It may also have an internal ocean. Titan’s big drawback is that it’s very cold. But further underground, where internal, tidal heating can provide more warmth, Titan could not only be a future home for humanity but may have once been a past home. Unlike Mars and Venus however, Titan is still relatively habitable; so why would an intelligent species have left and come to Earth? Sure, Earth is definitely a friendlier planet, but it seems unlikely that every member of a species would decide to move unanimously without some cataclysmic event to motivate them.

Of course, it’s also possible that alien migrants came to Earth from another star system entirely. It’s estimated that about half of sun-like stars could have a rocky planet capable of supporting liquid water on its surface. That adds up to 300 million potentially habitable planets in our galaxy. Sure, travelling between star systems might take a long time even with the most advanced technology possible. But the universe has been around for 13.8 billion years. The solar system formed 4.5 billion years ago. This means that intelligent life forms could have evolved even before our solar system existed. It’s not impossible that an alien race spotted Earth at some point and decided to populate it – much as humans hope to go forth and eventually establish settlements of their own.

Of course, unless we actually encounter progenitor aliens or find the planet they came from, we’re probably better off assuming we did just come from Earth. After all, the simplest solution is usually correct. And there’s also the fact that we haven’t found any relics of interstellar spaceships here on Earth. Nor do we have any record of this being our history; you’d think that aliens would have wanted to preserve and pass on such knowledge. Wouldn’t you want your kids to know if you were born on a different planet millions of miles away?

Sure, perhaps some cataclysm in the past destroyed extraterrestrial technology - accounting for the slow rise of civilization in recorded human history. But what could cause such a catastrophe? This is another assumption that requires even more explanation. There’s also the wealth of evidence for our evolution from much less intellectually sophisticated ancestors.

It may be theoretically possible for an advanced, alien race to have come and populated Earth at some point in the planet’s long past. But it makes far more sense for us to have been on Earth all along. And that’s why humans probably didn’t move to Earth from another planet.