The pretty far reaching study we blogged last week, about Octopi coming from outer space, is really most likely, probably, near certainly not true.
For evidence of the panspermia hypothesis, the authors wrote in their new paper, skeptics need only look to the octopus.
Octopuses have complex nervous systems, camera-like eyes and a capacity for camouflage that evolved suddenly and without precedent in their family tree, according to the study authors. The genes for these adaptations, the authors wrote, do not seem to have come from octopus ancestors, but "it is plausible then to suggest [these traits] seem to be borrowed from a far distant 'future' in terms of terrestrial evolution, or more realistically from the cosmos at large."
In one theory laid out in the paper, the authors posit that fertilized octopus eggs crashed into the sea aboard an icy comet at the onset of the Cambrian explosion. Another explanation, they propose, could be that an extraterrestrial virus infected a population of early squid, causing them to evolve rapidly into octopuses as we know them today.
Other researchers were not quick to embrace this theory. "There's no question, early biology is fascinating — but I think this, if anything, is counterproductive," Ken Stedman, a virologist and professor of biology at Portland State University, told Live Science. "Many of the claims in this paper are beyond speculative, and not even really looking at the literature."
For example, Stedman said, the octopus genome was mapped in 2015. While it indeed contained many surprises, one relevant finding was that octopus nervous system genes split from the squid's only around 135 million years ago — long after the Cambrian explosion.
Stedman added that, for a virus, such as the RNA-based ones known as retroviruses, to somehow turn a squid into an octopus, that virus would have to evolve on a world where squid were already plentiful.
Modern retroviruses have evolved to be extremely specific about which hosts they infect, Stedman said. But a retrovirus from outer space wouldn't have evolved to be specific for Earth-based creatures, and "certainly not specific enough for something like a squid — unless you have massive amounts of squids on some planet incredibly close to us that is spitting off all of these meteors. But I think that kind of assumption is highly unlikely," Stedman said.
Karin Mölling, a virologist at the Max Planck Institute for Molecular Genetics in Germany, echoed this sentiment in a piece of commentary published alongside the new paper.
While the new study is "very useful" for thinking about the influence of the universe on our planet in new ways, the findings "cannot be taken seriously," Mölling wrote. "There is no evidence for it at all."