Wednesday 9 March 2016

evolution - How did viruses come to be?



My question is out of curiosity and got me thinking. How did viruses with the head, tail and tail fibres actually evolve? These viruses look more like machines than biological entities. Are there any theories to how these viruses evolved?



Answer



I found a book chapter for you here


Quick summary: 3 hypotheses to Origin of viruses



  1. From pre-cellular world (virus first hypothesis)

  2. From reductive evolution of parasites (reduction hypothesis)

  3. From fragments of cellular genetic material (escape hypothesis)


Drawbacks:




  1. virus require cells (to infect) so how can they come first

  2. virus do not look like known reduced parasites from Bacteria/Eukarya/Archaea

  3. unlikely that genetic fragments form complex viral structures for viral function



Because of these drawbacks, the problem of virus origin was for a long time considered untractable and not worth serious consideration



The rest of the chapter looks more in-depth into the 3 hypotheses


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