Enigmatic viruses –not living, yet not dead–help create, protect and transform the universe, observed Carl Zimmer in his classic A Planet of Viruses. Viruses, he notes, have had a huge impact on the history of all life on Earth–their population of Earth’s Oceans would stretch out into space 42 million light years.
It was in the oceans that cover 2/3s of our planet, that life got its start. The oldest traces of life are fossils of marine microbes dating back almost 3.5 billion years.
“It was in the oceans,” Zimmer observes, “that multicellular organisms evolved; their oldest fossils date back to about 2 billion years ago. In fact, our own ancestors did not crawl onto land until about 400 million years ago.””
“Could Thrive on Inhabited Worlds”
“If other planets host life that is similar to ours (for example DNA and RNA, evolution by natural selection, etc.) then I think it is very likely that viruses will exist there, too,” University of Washington astrobiologist, Rory Barnes, in the Virtual Planetary Laboratory primarily interested in the formation and evolution of habitable planets, wrote in an email to The Daily Galaxy. “The overall fitness of viruses,” he continued, “that is their widespread adaptation to local environments, suggests they could thrive on inhabited worlds. I also agree that the threat from alien viruses, even if we travel to their home worlds, is minimal. Earth-bound viruses have adapted to the life around them, so unless the alien life is extremely similar to Earth life, they are unlikely to pose a threat. The caveat is that if the Universe is only able to support life forms that rely on the same set of biomolecules as terrestrial life, then we could be susceptible to their attacks.”
Arizona State University astrophysicist Paul Davies warns that viruses may not only be found on Earth, but might occur on habitable planets elsewhere in the universe. Davies suggests that a wide range of microbes and other microscopic agents would probably be needed to support life as a whole, whatever form it takes and that viruses could be part of the equation.
“Viruses actually form part of the web of life,” Davies told The Guardian in an interview. “I would expect that if you’ve got microbial life on another planet, you’re bound to have – if it’s going to be sustainable and sustained – the full complexity and robustness that will go with being able to exchange genetic information.
“A friend of mine thinks most, but certainly a significant fraction, of the human genome is actually of viral origin,” said Davies in his Guardian discussion, whose new book, What’s Eating the Universe?, observes that genetic material from viruses has been incorporated into the genomes of humans and other animals by a process known as horizontal gene transfer. It’s unlikely, Davies suggests, that alien life would be homogenous.
“I don’t think it’s a matter that you go to some other planet, and there will just be one type of microbe and it’s perfectly happy. I think it’s got to be a whole ecosystem,” he added. “The dangerous viruses are those that are very closely adapted to their hosts,” he said. “If there is a truly alien virus, then chances are it wouldn’t be remotely dangerous.”
Bringers of Balance and Drivers of Innovation?
“From the perspective of being locked in a single human body for a single human lifetime, viruses can appear to be a nuisance at best, a global catastrophe at worst.”, astrobiologist Michael L. Wong and the host of a podcast called Strange New Worlds, told The Daily Galaxy. “But from the perspective of Earth’s biosphere over deep time, viruses may be recast as bringers of balance and drivers of innovation. Thus, I appreciate Davies’ perspective that virus-like entities would likely accompany an extraterrestrial system of cellular organisms—despite the fact that much uncertainty remains about the origin of viruses and life in general.”
“Most people think about, well, we would need to have a very large spacecraft, and then sort of recycle things for the very long journey, and then all the technology you’d need to take,” Davies said. “Actually, the toughest part of this problem is what would be the microbiology that you’d have to take – it’s no good just taking a few pigs and potatoes and things like that and hoping when you get to the other end it’ll all be wonderful and self sustainable.”
Among their positive roles, viruses that infect bacteria – known as phages – can help keep bacterial populations in check, while viruses have also been linked to a host of other important processes, from helping plants survive in extremely hot soils to influencing biogeochemical cycles, reports The Guardian. And, as Davies notes, a significant fraction of the human genome may be remnants of ancient viruses.
“I can get behind the idea that extraterrestrial organisms depend on rich ecosystems as well as genetic information transfer by virus-like entities,” UCLA astrobiologist Jean-Luc Margot told The Daily Galaxy. “To put these speculative ideas to the test and improve our understanding of life, we need to sustain efforts to find extraterrestrial life.”
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