Giant viruses cast doubt on a common ancestor of all life forms
|July 30, 2013||Posted by News under Biology, News|
And suggest quite the opposite pattern.
Further to the giant viruses we have been writing about (here and here) Caroline Crocker explains at AITSE that the question of whether viruses can be considered life (and if not, what are they?) helped motivate her to pick her major in microbiology:
The teacher explained that viruses do not meet any of the criteria we use to use to assess whether something is alive:
They do not reproduce themselves;
They do not transform energy (they don’t eat);
They don’t respond to their environment;
They are not made of cells; and
They don’t grow.
Therefore, even though viruses do cause us a lot of trouble by hijacking our cells and forcing them to make virus instead of performing the functions of life, technically they are not alive. And, having never been alive, they are not dead. Are they the undead?
Giant viruses are bigger than cells and have only 7% similar genomes to them.
Basically, here’s the problem:
The scientists speculate that these giant viruses evolved from cells (becoming simpler), but since the DNA doesn’t actually match any living cells, they suggest that perhaps “at some point, the dynasty on Earth was much bigger…” So, even though evolutionary theory says that all of life evolved from a common ancestor, becoming more and more complex and diverse, the existence of these giant viruses makes these scientists suggest the opposite scenario.
Bet you didn’t hear it explained that way before: These viruses are overturning definitions that define biology.