Cambrian Explosion : Octopus could have come directly from space

Cause of Cambrian Explosion - Terrestrial or Cosmic ?

Is the octopus an "extraterrestrial import" that arrived on Earth via a comet? A study resurrects the controversial theory that life began elsewhere in the universe and claims that the foreign viruses that rain on our planet have led evolution. The Cambrian explosion refers to a very particular period of the Earth, marked by the sudden appearance of the majority of multicellular organisms as well as an extremely rapid and complex genetic diversification of animal, plant and bacterial species. If the generally advanced hypotheses imply purely terrestrial mechanisms, a study co-signed by more than 30 geneticists, paleobiologists and astrobiologists proposes an extraterrestrial origin to this event, especially concerning the unique case of the octopus.

The Cambrian era is the first geological period 541 million years ago. Then, suddenly, simple unicellular life goes into complex multicellular life, accompanied by rapid genetic diversification. Most scenarios explaining the Cambrian explosion are based on environmental changes, embryonic genetic changes or ecological changes. Apart from these terrestrial explanations, another hypothesis published in Progress in Biophysics and Molecular Biology, has been proposed by an international collaboration of paleobiologists, geneticists, astrobiologists and biochemists. This one proposes a cosmic origin to the Cambrian explosion.

• The first is that genetic diversification has been triggered by the appearance of retroviruses, known to integrate multicellular genomes and make significant changes.

• The second concerns octopus, and suggests that, given the extreme complexity of these organisms, they could have come directly from space in the form of eggs.

• Finally, the third uses recent atmospheric and cometary biomolecule detection data to explain how comets have brought life to Earth.

In 1974, British astrophysicists and astrobiologists Chandra Wickramasinghe and Fred Hoyle deepened the model of panspermia to explain some sudden developments and events concerning the diversification of life. The authors of the study review the work of the two scientists to provide an explanation for the Cambrian explosion. The recent discovery of about 4.2 billion-year-old microorganisms in Canadian stromatolites may challenge the classic scenario of abiogenesis. If the conditions on the Earth's surface are too hostile for life to appear on its surface by itself, then its origin is not to be found initially on Earth, but in the comets and asteroids of the Earth. 'Hadean.

The purely terrestrial explanations of the Cambrian explosion can not account alone for the "brutal" appearance of metazoans and the emergence of a concomitant genetic complexity. The appearance of life itself is generally explained by the scenario of abiogenesis, that is to say the passage of non living organic matter terrestrial molecules to life. Rejecting abiogenesis for its lack of coherence, some scientists have advanced the theory of panspermia. Panspermia is a hypothesis that at least some of life on Earth has an extraterrestrial origin. Scientists have shown that complex molecules such as RNA, DNA, viruses and even bacteria can survive space travel by being contained in bodies such as asteroids or comets. By bombarding planets, these vectors can thus propagate the bases of life, even life itself everywhere in the universe, when the planetary conditions are reunited for it to emerge. Several studies have given credit to the theory of panspermia.

Transported within comets and thanks to their nanometric size, they would be safe from ionizing radiation and could cross the space while preserving their integrity. Thus, retroviruses would have played the main role in genetic diversification of species during the Cambrian explosion, allowing many organisms to mutate while also bringing new genes causing the sudden explosion of genetics found in the Cambrian.

The genome of the octopus shows an extraordinary complexity; compared to the Homo sapiens genome, it contains 33'000 additional coding genes. The history of evolution of cephalopods dates back more than 500 million years but has many gray areas. The case of the octopus particularly arouses by the sudden appearance of an impressive organic sophistication: big brain, complex nervous system etc. Genetic transformation is unique and not found in any pre-existing living organism; these genes could therefore be of extraterrestrial origin. Such a qualitative and quantitative gap with the other species is impressive and constitutes a real leap in the genetic strategy. This unique property can not, according to the authors, be explained by the simple assumption Darwinism, which would like these extraordinary genetic properties to be the fruit of a slow evolution shaped by mutations, given the suddenness of their appearance.

The hypothesis put forward by the authors is that these unique genes would have been brought by comets or asteroids, either via the RNA contained in retroviruses, or directly by cryopreserved octopus eggs. Indeed, the existence of extraterrestrial retroviruses could explain the fulgurating emergence of the genetic complexity of octopus. Thanks to the genomic integration of unique coding genes, these retroviruses could have provided the genetic boost found in cephalopods. The cosmic origin of certain genes would also provide an explanation for certain genetic characteristics found in some species, still unexplained today.

Cause of Cambrian Explosion Terrestrial or Cosmic ?https://www.sciencedirect.com/science/article/pii/S0079610718300798

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