It seems like a safe rule to disregard any conspiracy theory that expects the government both to orchestrate prominent events/disasters flawlessly (cough) and to cover them up perfectly. When it comes to which insultingly-stupid theory irritates me the most I confess to going back and forth between the we-blew-up-the-WTC rumors and the idea that a government, apparently ours, somehow manufactured HIV. Thankfully we can finally put the latter, at least, to bed:
RESEARCHERS have traced the origin of HIV — the virus that causes Aids — to chimpanzees in southern Cameroon.
A virus identified in apes living in forests south of the Sanaga River is the closestfound to the human immunodeficiency virus.
The discovery bolsters the standard theory that the Aids epidemic began after an ape version of HIV crossed into people, most likely infecting a bushmeat hunter first.
Some conspiracy theorists have suggested that the virus was created in a bioweapons laboratory.
Another controversial hypothesis, advanced by the journalist Edward Hooper, holds that the epidemic began with a batch of contaminated polio vaccine in what is now the Democratic Republic of Congo. Neither scenario fits with the latest evidence.
Like many other human epidemics (for example, ebola) the virus persists in its original host without causing any apparent harm:
As well as solving the mystery of the origin of the virus, the findings prepare the way for future work exploring the history and behaviour of the simian form of HIV in its natural host.
SIVcpz does not cause an Aids-like illness among chimpanzees, despite its similarity to the human virus and the very close genetic relationship between chimps and humans. Finding out why this is so could ultimately help scientists to understand the workings of HIV. Professor Sharp said: “We are currently working to understand which genetic differences between SIVcpz and HIV-1 evolved as a response to the species jump.”
The simple reason for this is that the virus has burned its way through chimpanzee populations for thousands of years, a long enough time for the virions which do not kill their host, at least not quickly, to outcompete the most lethal strains. When a virus meets a new species for the first time it will burn through the immunologically-naive animals mercilessly, until a period of coevolution takes place in which resistance alleles spread in the host populations and the fiercest strains of virus lose out to strains which keep the host alive long enough to spread more widely.
Some human diseases have made that transition in the space of recorded history, for example over six hundred years syphillis declined from a horrific short-term death sentence to a treatable long-term nuisance. Populations suffering today can take minimal consolation in knowing that HIV will follow that trajectory as earlier epidemics before it, and further we simply cannot know the time course that the de-virulence process will take if we leave it to evolutionary chance. Now that science can study how exactly the current state of chimp-virus detente was reached at the very least we may have more opportunities to nudge chance along.