They are kind of weird and suspicious-looking, octopuses — and no, it's not octopi, experts say — but are they really space aliens?
No, they are not, despite an obscure scientific journal raising the suggestion and triggering on Wednesday some credulous Brit tabloid news.
It's a fun idea, but "cannot be taken seriously," writes molecular geneticist Karin Moelling of Germany's Max Planck Institute Molecular Genetics, who was asked to review the report by the journal that published it.
There are quite a few reasons why the paper's basic thesis that space genes are landing on Earth — in the form of frozen viruses and octopus eggs — is bonkers, Moelling writes, but chiefly "there is no evidence for it at all."
The Progress in Biophysics and Molecular Biology report from March looked for an explanation for the "Cambrian explosion," a rapid outburst of different animal body types that appear in the fossil record about 500 million years ago.
Written by scientists associated with the "Panspermia" — an idea proposed in the 1970s that suggests alien life was seeded the Earth billions of years ago — the study finds evidence for the notion in the genes of the famously clever, agile, and camouflaged octopus.
This toolkit of genes for these capabilities is so remarkable, writes the review team led by Australian astrobiologist Edward Steele, it is "plausible then to suggest they seem to be borrowed from a far distant 'future' in terms of terrestrial evolution, or more realistically from the cosmos at large."
They appeared, the report suggested, "most plausibly as an already coherent group of functioning genes within (say) cryopreserved and matrix protected fertilized Octopus eggs."
"Plausibly" is such a fun word.
So anyway, one problem with this idea is that octopuses' nervous-system genes split from squids' only around 135 million years ago, much later than the Cambrian explosion, according to the report of the octopus genome first mapped in 2015.
Overall, the genes of the octopus are nothing special, that genome showed. "We found a fairly standard set of developmentally important transcription factors and signalling pathway genes," wrote the authors, "suggesting that the evolution of the cephalopod body plan did not require extreme expansions of these ‘toolkit’ genes."
In other words, its evolution wasn't anything remarkable. Its genes looked comfortably related to squids and nautilus, the shelled squid-like mollusks that are ancestors of octopuses. (In fact, octopuses are a famous example of convergent evolution, in which genetically unrelated species develop structures — in this case, eyes — that resemble ones found in other animals.)
Octopus genes sit squarely on the genetic family tree of all Earthly life, which goes back at least 3.77 billion years.
Another problem with the idea that gene-filled meteorites are raining on Earth is that we have a fairly extensive collection of meteorites in museums, and there doesn't seem to be any genetic material in them. A 1996 report that a Martian meteorite contained microfossil briefly electrified the world, and played a small weird role in a sex scandal during the Clinton administration, but it has been pretty widely discounted by scientists, who have been looking hard for any evidence of alien life in these rocks ever since.
The Cambrian explosion, which lasted from about 541 million years ago to 485 million years ago, already has a lot of simpler explanations, Moelling noted, ranging from animals moving onto land, breathing oxygen, developing collagen, and eyes.
"So this article is useful, calling for attention, and it is worth thinking about," she concluded. "Yet the main statement about viruses, microbes and even animals which came to us from space, cannot be taken seriously."