What If Humans Were Silicon-Based Instead of Carbon-Based?

OK, if you’re a regular viewer of What If, you know we’ve already explored the idea of finding silicon-based alien life. But what if we didn’t have to venture far off into the Universe to find these lifeforms? What if you were the one made of silicon instead of carbon? How would silicon-based life have evolved? What would your new human body be like? And how different would Earth need to be for a silicon version of you to exist?

Carbon is a bit of an attention hog. And for good reason. All life on our planet shares carbon as its primary building block. 18% of your own body is made of carbon. Without it, you’d have no DNA. On the other hand, silicon is one of the most abundant elements on Earth, second only to oxygen. Approximately 25 to 30% of our planet’s crust is made up of the stuff.

The potential for silicon-based life was first suggested in 1891 by astronomer Julius Scheiner. The hypothesis is based on the chemical similarities between carbon and silicon. Both elements bond with oxygen to form polymers. In other words, large molecular structures. However, when silicon reacts with oxygen on Earth, it forms silicon dioxide.

This solid, also known as silica, is a key ingredient in sand. And less naturally, silicon and oxygen can be found together in the synthetic compound known as silicone. This liquid or rubbery substance is in everything from electronics to oven mitts, not to mention breast implants. But these silicon-based compounds can’t support life. Unless you’re talking about the What If universe.

Even though they have a lot of chemical similarities, if human life was based on silicon instead of carbon, everything would be very different. While both elements are able to form double bonds with oxygen, the bonds formed by silicon are typically weaker. That means silicon-based life on Earth would be simple and primitive.

There’s no way that your body in its current complex form of organs, bones and tissues, could exist. Yeah,say goodbye to the human shape as you know it. You’d now be a blob of silicon compounds. And not just humans. Every living thing on Earth would likely be some kind of blob too. It would actually be a miracle that you’d exist at all.

It would also be highly unlikely for a simple lifeform like you to be able to successfully reproduce. You’d be too fragile. This would be especially important when thinking about how this silicon-based life would have begun on Earth in the first place. Chemical life needs to exist in a medium that lets molecules move around. For carbon, liquid water is the perfect medium.

Water can carry things into and out of the cell. But water wouldn’t support the development of your new human chemistry. The double bonds of silicon would break down into single bonds in the presence of H2O. That means instead of evolving into the stellar example of flesh and bone that you are today, you’d turn into a silicate rock.

Silicon-based life would need a different liquid to be the common binding element of life. One medium that could work is sulfuric acid. That’s because the silicon structures that normally break down in water, would be more stable in sulfuric acid. The implications of this would go far beyond every lifeform on Earth being completely different.

Now the whole planet would be different too. Not only would life need oceans of sulfuric acid to spring out of, the atmosphere would need a major overhaul. Silicon-based life wouldn’t necessarily need oxygen. Because silicon would react with oxygen the same way it would react with water. It would turn into a rock. Temperatures on Earth would also have to change dramatically.

Made from silicon, you’d need an extremely warm environment in order to thrive. By extremely warm, I mean unbearably hot. The melting point of silicon is 1,410 °C (2,570 °F). Yeah, in other words, for this element to exist in any form other than a solid, Earth would have to be a very toasty, very acidic place. And scattered across it would be billions of blobs of life completely incapable of reproducing.

The odds of those blobs evolving into intelligent life like the carbon you? Well, sorry to say, but it appears we’ve wandered into science fiction territory. Imagining the possibility of silicon-based Earthlings raises many big questions. Like how did life begin on our planet? And what conditions are necessary for life to continue to evolve? But also what would happen if things went in a different direction?

Whatever the answers to those questions may be, life flourished here on Earth the way it did. And it was the perfect carbon-based recipe for you to become the human you are. And who knows? Maybe life didn’t really originate here on Earth after all.