posted on Sep, 1 2012 @ 05:47 PM
reply to post by Ayana
But on the other hand, viruses could do none of the criteria for living without a host to bring it about.
I think this is the ultimate line to consider when discussing whether or not viruses are alive.
However - the points you mention are very good ones.
I do it often, but for good reason; I will evoke the Red Queen: The Red Queen Hypothesis sets the groundwork for a new understanding of life, in
general. If viruses didn't exist, we would all reproduce asexually, and multi-celled organisms may never have evolved.
Viruses have evolved alongside life - however it was they first came about - and have been one of the primary factors influencing natural selection -
even more powerful than the environment in many cases.
I no longer think it's completely accurate to think of life as being separate from viruses. Not that viruses are alive, per se, but that it is an
anterior companion to life. Much how the Earth's geological functions are largely influenced (when not directly caused) by the moon - not entirely
separate from Earth, but not really Earth, either. The two together, however, form a system that has been conducive to life as we know it.
Wiki on Red Queen Hypothesis: en.wikipedia.org...
Other links of interest:
&recomb.html - examines real-world data
When the bacteria were unable to adapt themselves, the rate of virus evolution slowed down to almost half that seen when the two species were
allowed to evolve in tandem. What's more, the team found there was much less genetic variation in the resulting virus populations than those that
co-evolved with the bacteria under Red Queen evolution.
"Together, our findings suggest that it is the interactions between species that are the main drivers of evolution. And by causing rapid divergence,
they could even lead to speciation itself," said Dr Brockhurst.
The bacteria seem to gain nothing from this transaction. In fact, if this is proto-sex, it’s proto-bad-sex, because neither bacterium can be
described as consenting. The plasmid contains the quintessential selfish gene, a bit of DNA whose only mission is to reproduce itself, thus driving
the plasmid to distribute as many copies of itself to as many hosts as possible. In the process, bits of the original bacterium’s genome
occasionally cling to the plasmid like foxtails on a dog’s coat and find themselves in the new host. Eventually, explains Rose, some hosts begin to
use and benefit from the inadvertent gift of another individual’s DNA.
Rose and Hickey have gone on to propose that selfish DNA could account for a primitive form of sex that’s closer to sex as we now know it. In some
early single-celled organisms, they theorize, selfish DNA didn’t merely cause a bridge to form so that it could travel from one individual to
another--it impelled the two organisms to actually fuse, in a primitive anticipation of what sperm and egg do during fertilization. This parasitic DNA
could then spread contagiously until the whole population was committed to sex.
This parasitic gene theory has also been proposed to explain the origin of males. While I'm sure that garners a bit of a laugh - an asexual or
hermaphrodite population would be driven to extinction by a the 'parasitic' genetic material now contained in the Y-chromosome (a very small and
stunted chromosome by comparison to all others). The surviving adaptation was the ejection of that bit of genetic material into its own
Earlier theorists had assumed that sex was advantageous in the long run because it produced variability in gross features like size and shape,
thus equipping species to adapt and roll with the inevitable environmental punches. If that were the case, then sexual organisms ought to turn up in
harsh areas on the frontiers of an organism’s habitat, and clones ought to live only in cushy environments. In fact, nearly the opposite is true:
clones tend to predominate in frontier settings, while sexual organisms fill the niches in environmentally stable zones
Which goes along with my opinion that viruses shouldn't really be considered apart from their hosts. Even if they're not alive.