ZME Science has a great post about the online controversy about the Octopus genome. Cephalopods are not aliens and the author Mihai Andrei does a great job explaining why.
The new study, penned by over 30 researchers, essentially rehashes the theory of panspermia — the idea that life on Earth emerged in outer space, hitching a ride on meteorites or other objects that crashed into Earth at one point, something often referred to as the Hoyle-Wickramasinghe (H-W) thesis of cosmic biology.
The research starts from the Cambrian Explosion an event approximately 541 million years ago, during an age called the Cambrian period. The Cambrian Explosion was an age of extreme diversification of life, during which most major animal phyla started to emerge. The study’s authors question whether that happened naturally, with just the elements existing on Earth.
“One particular focus are the recent studies which date the emergence of the complex retroviruses of vertebrate lines at or just before the Cambrian Explosion of ∼500 Ma. Such viruses are known to be plausibly associated with major evolutionary genomic processes. We believe this coincidence is not fortuitous but is consistent with a key prediction of H-W theory whereby major extinction-diversification evolutionary boundaries coincide with virus-bearing cometary-bolide bombardment events,” the study reads.
In other words, what they’re saying is that life didn’t just emerge on its own, it was “seeded” from life-bearing comets that pummeled our planet at various times throughout history. These comets could have brought a myriad of novel life-forms from other planets, including viruses. This is one of the main assumptions of the H-W thesis — that small bodies such as asteroids and comets can protect the “seeds of life”, including DNA and RNA. So far, so good; this is a plausible idea, that has been investigated since the 1970s and continues to be analyzed by various groups. There’s not much evidence to say that it did happen, but with what we know so far, it might have happened.
Then, the authors make a big leap: if you’re not convinced by the panspermia theory, you need not look farther than the octopus. Octopuses have very complex nervous systems and big, specialized eyes — two unprecedented features.
“A second focus is the remarkable evolution of intelligent complexity (Cephalopods) culminating in the emergence of the Octopus,” the study continues.
This is where it starts to get thorny. Cephalopods, the group in which octopuses belong, did emerge in the Cambrian — the fossil records clearly suggest so. But the early cephalopods were Nautiloids, a very diverse group of creatures which exist to this day. But Nautiloids look completely different to octopuses, and they don’t share many of their impressive features. In fact, octopuses didn’t emerge until the Devonian, 323 million years ago. This means that there’s a window of over 200 million years from the Cambrian explosion to when the first true octopuses emerged, which is plenty of time to selectively develop specialized features (there are studies which say octopuses developed a bit earlier, but not significantly in this context).
