On August 14, a writer for Geek.com, Meredith Placko, posted a story with this headline: "Scientists Declare That Octopuses Are Basically Aliens." If you have a Facebook account, you certainly saw this headline in your news feed. And if you bothered to read the post, you would have learned that American and Japanese researchers have sequenced the sea creature's genome and found its DNA structure to be so strange that it seemed to have evolved on another planet. Weirder yet, octopuses can even change their genetic code.
The problem I have with Placko's post is that it framed alienness as a matter of DNA. And this was not an accident but an inevitable consequence of the public's hyperfocus on genetic information. But, no matter how crazy an animal's DNA might appear, it is probably from this planet if its cells contain the energy-generating organelles called mitochondria.
Now, before I go a little deeper, a quick explanation is in order. There are three branches of life: archaea, bacteria, and eukaryotes. The first two can be grouped together as prokaryotes. And so effectively, there are only two: prokaryotes (cells without a nucleus) and eukaryotes (cells with a nucleus). The former are much, much older than the latter. Also, the former are much, much, much simpler than the latter.
Eukaryotes are huge, and when combined can emerge as something as monstrous as a whale. Almost all eukaryotes have mitochondria, the powerhouses of the cell, and all multicellular eukaryotes (animals, plants, and so on) have them. So if you tell me octopuses don't have mitochondria, then I will begin to believe they are indeed from a place far, far away. And I will believe this for deeper reasons than any of this flimsy DNA business could ever provide. In short, I have a view of life that corresponds with the British biochemist and science writer Nick Lane.
Lane has written four books, the latest of which is The Vital Question: Why Is Life the Way It Is? In his books, we find a mind that is looking for the answers of life not in information processes but in energetic ones. And this makes a lot of sense. Before matter becomes alive, it must be aggravated, disturbed, swirled, turned over and over. Things first need to get going, and things get going only if there is a constant flow of energy. While everyone can't stop talking about James Watson and Francis Crick, Lane can't stop talking about Peter Mitchell—the practically unknown British scientist who figured out how adenosine triphosphate (ATP), the energy currency of life, is produced. You worship DNA; Lane worships ATP.
And while everyone is looking at the double helix, Lane can't take his eyes off the mitochondria, which for him represent the key to how life moved from simple prokaryotes to massive and complicated eukaryotes. But the leap from prokaryotes to eukaryotes is just fucking staggering. It's as if one day you had an abacus, and the next day an iPhone. What he wants to explain is how life got from one to the other. Lane's answer is mitochondria.
The details of the theory are complex and sometimes full of jargon, but what you need to know for now is that mitochondria, as with chloroplasts (which are found in plants), descended from bacteria. Somehow, a little bacterium ended up inside a big one, and it turned out not to be a bad deal. One (mitochondria) provided energy, and the other provided a home. How this happened is not known. But it did happen. With this chance symbiosis, life was presented with a new evolutionary landscape that led to greater and greater complexity. What drove cell and multicellular complexity were mitochondria.
Without this accidental relationship, Lane explains, life on earth would have remained at the level of archaea and bacteria. If one has this understanding of things, which I think is close to the truth, one will not expect to find women or crabs roaming about Mars, as recent memes suggest. That form of life is highly improbable. Prokaryotes, on the other hand, are much more likely to be in seas and in the ground of other planets. (Lane bets on thermally active ocean floors.)
Lastly, if we come across aliens, we should try to cook them. They are most likely made of much the same biological stuff as we find on earth.