Regressive evolution proposes that viruses descend from free-living and more complex parasites.  According to this theory, ancestral viruses developed a growing dependence on host-cell intracellular ‘‘machinery’’ through evolutionary time, while retaining the ability to auto-replicate, like mitochondria that have their own genetic information and replicate on their own (Bubanovic 869).  Because scientists have very little information on the origins of viruses, the regressive evolution theory is just one of the many theorizes option that scientists have chosen to suggest how viruses began.

Evolution is a scientific fact.  Hundreds of thousands of species have co-evolved with their environments and to protect against being attacked by any number of threats.  Viruses are not that different from these species.  They require a host to survive, and they replicate hundreds of times which eventually causes a disease in the host.  Scientists believe that “according to this way of thinking, viruses probably co-evolve with their hosts, like any ‘good parasite’” (Bubanovic 869).  Therefore, it stands to reason that viruses also evolve to protect against medicines and vaccines that would otherwise kill them, which is why many STDs do not have a cure.

It is not very far fetched to believe that viruses, through the process of evolution, have also eliminated unnecessary traits that are not required to function, or that may have a hindrance on functionality.  With this being the case, it is likely that viruses may have originally evolved from independent organisms that only latched only behaved parasitically, to becoming completely dependent on the host for resources and now co-evolves with the host.  Nevertheless, it is important to study the origin of viruses because we may be able to find out the cause of their existence and the ultimate cure for many of the viral diseases that currently are incurable in the medical field today.