|A virus that infects bacteria and the common flu virus|
Lay folk often consider evolution as a progressive process: a determinative mechanism forever forging more complex systems culminating in highly evolved and intelligent organisms. This is not how evolution works. Evolution is not deterministic in any meaningful, progressive sense. It is essentially a blind, indifferent process which does not necessarily result in more complex organisms, just those more successful, and those best able to cope with the current environmental challenge. This process is illustrated well by contemplating the 'Virus'. There is little doubt that viruses are successful from an evolutionary perspective. However, they are relatively simple entities even when compared to bacteria. Notice, I called viruses entities and not life. Most biologists don't consider viruses as constituting life at all, as defined by biological criteria. Their activities occupy a border area between chemistry and life. Humans like to categorise and place things into neat and orderly arranged boxes. Classification systems are a useful way to order knowledge and enable our brains to cope and explain complex phenomena. However, classification, although not necessarily arbitrary, is an artificial but useful, human construct. Things which defy natural classification make us feel intellectually uncomfortable. Viruses defy neat and discrete classification. They seem to oscillate somewhere between chemical reactions and basic existence; our minds balk at the irregular and unclassified. I find it fascinating that something not considered alive is subject to evolutionary forces, nonetheless. Perhaps our current definition of what constitutes life requires a rethink.
Although not live in any conventional sense, they are capable of having a major biological impact. A virus consists of strands of DNA or RNA encapsulated in a protein matrix, or coat. That is about as complex as they get. They require a host cell to begin to manufacture and replicate. Once inside the host, the few genes they carry hijack the cellular apparatus and persuade the cell to manufacture viral genetic material and a new shiny, protein coat. This process continues until the host cell bursts to release the new assembled viral particles which disperse to infect cells of their own. And so the process continues...... This is what happens when a virus causes disease. Viruses are truly parasitic if they cause harm to the host. Most viruses don't act this way. They simply hitch a ride. The DNA links into the host cells’ DNA, and there the viral DNA stays, integrated in a form of suspended animation. They don't cause disease and go unnoticed by the host organism.
The ability of viral particles to exchange pieces of genetic material is thought to be an important process in evolution itself. Not only can they drop off bits of their own DNA, they can transfer host DNA between species. It is thought that about 10% of the human genome consists of DNA inserted by viruses. Some of this foreign genetic material has been with us for many millions of years and over eons has mutated and evolved into active genes.
Alive, or no, viruses are, from an evolutionary point of view, very successful. A recent estimate suggests that there are about 320,000 different 'types' of viruses which are capable of infecting mammals. When you consider that virtually every organism on earth, including plant life and bacteria, contain viruses then the total number of diverse types is staggering to ponder. At best we can only estimate, but even a conservative guess would place the final number in the many millions and this could rise to the billions. Now, that is an evolutionary success story, especially as they have been around for at least 3 billion years. This is not bad for something that doesn't fulfil the biological criteria for life. All this achieved by simplicity, non-intelligence and non-sentient incomprehension. You can be assured that viruses will continue not to be alive long after the last human has relinquished his/her hold on real life.
But please don't tell the religious fundamentalists. They won’t believe you anyway as they still think the earth is only 6,000 years and that man has a special and exalted position on God’s earth. Don't tell it to the virus either, they won't listen, they don't have to.
|Hey, hang on guys, where are your mates? I've got a list|