Trust Me, I’m A Scientist — Evan Martin
Ah, the origin of life. One of the great mysteries of the universe that has confounded the greatest human minds for millennia. It’s a question that we all want to know the answer to, but likely never will. Thus, it’s no surprise that every single human culture ever known has some sort of lore about where we came from. Here in North America, most of those tales involve bearded men who herded goats around the Middle East and North Africa while talking to God about which tribe in that region was His most favoritest.
Wait, did I say we’ll never know the answer? Scratch that, it turns out we already do. So here, I give you the actual true story of where life came from. But first, a short disclaimer.
The basics of abiogenesis (aka life coming from non-life) are pretty well established in terms of the steps that had to happen, but there’s still significant disagreement over the details. For the purposes of this column, I’m going to stick to what we know with decent certainty. Still, this is a column for a humor magazine, so take it with a grain of salt. Ok, so here goes:
It all started in the beginning. Well, actually, 10 billion years after the beginning of the universe. Fast forward to 3.5 billion years ago; our solar system and all its planets have been around for about one billion years thus far. The Earth is covered in an ocean, containing dissolved iron and carbonate minerals, kept warm by the Earth’s still-hot core. The atmosphere contains water vapor, ammonia, carbon monoxide and other trace gases. Of course, when you have water vapor, you have clouds, and when you have clouds, you get lightning storms. Put this whole system together and organic molecules, such as amino acids, form spontaneously in the ocean. Still with me? Good.
Now we have an Earth covered in a warm ocean full of organic molecules. Still, there is no life yet—although the reactions that form these molecules are some of the very first biochemical pathways. And as these molecules float around, they interact with each other. And when they interact, they follow the same rules that organic chemistry does now: They form the most stable products possible. Again, no life yet—but certain molecules are being favored in chemical interactions. This is the earliest form of natural selection.
As these organic molecules—amino acids, fats, sugars, nucleic acids and others—float around and react with each other, they begin to form polymers, or large molecules, made of smaller repeating units. One polymer that eventually forms is ribonucleic acid, otherwise known as RNA. RNA is very similar to DNA except for one tiny difference on each smaller unit. And as biochemical pathways continue to get more and more complex, they begin to encode information through RNA, and then transform into DNA.
What does that mean? Basically, it means that the RNA can do two very important things: 1) It can use the specific combination of its smaller units to assemble a specific sequence of amino acids into polypeptides, or proteins, through chemical reactions, and 2) copy itself (almost) perfectly. To be fair, it is also possible that proteins appeared first, and were later encoded by RNA. Either way, the reactions of genes (RNA and DNA) and the structure of proteins became intertwined through spontaneous chemical reactions.
Finally, these pathways became enclosed in lipid membranes, made of mostly fatty acids, along with some proteins and sugars as well. And after this occurred, the first protocells were born. These ancient cells continued to reproduce, and, as they say, the rest is history.
Okay, okay, so maybe I exaggerated a bit when I claimed the basics of the history of life are well established, because there is still quite a bit we don’t know. But you know what? That’s the most exciting thing about science: that we don’t know everything. Sure, any mythology can give you an absolute(ly wrong) answer about where life came from, usually involving some sort of all powerful or nearly all-powerful being. But seriously, where’s the fun in that?
I don’t know about you, but I love the fact that we don’t know exactly where our very earliest single-celled ancestors came from, and probably never will for sure. So in lieu of a mythological answer to the origin of life, I invite you to go look up abiogenesis on Wikipedia. I wish I could write more about this (and I could, believe me). But I’ve hit my word limit, so it’s the best I can do.
Evan is the product of 85 million years of primate evolution. He enjoys sports, Star Wars, living in Cleveland and seeing the world as one giant science experiment with too many variables and not enough explosions.