Island-specific strains of the simian immunodeficiency virus (SIV), which infects monkeys such as the Bioko Drill, revealed the virus has been around thousands of years longer than previously thought.
Credit: Preston Marx, Tulane University
WASHINGTON: An HIV-like virus that infects monkeys is thousands of years older than previously thought and its slow evolution could have disturbing implications for humans, according to a new study.
Scientists said the simian immunodeficiency virus (SIV) - the ancestor to the human immunodeficiency virus (HIV) that causes AIDS - is probably between 32,000 and 75,000 years old and may even date back a million years.
"If it took thousands of years for SIV to evolve into a primarily non-lethal state, it would likely take a very long time for HIV to naturally follow the same trajectory," a statement from Tulane University said.
Older data brought into question
The work led by researchers from Tulane and the University of Arizona included a genetic analysis of SIV strains found in monkeys on Bioko, an island off the coast of what is now Cameroon which split off the continent of Africa after the ice age more than 10,000 years ago.
The study, published in Science, calls into question previous DNA sequencing data that estimated the virus's age at only a few hundred years.
"The biology and geography of SIV is such that it goes from the Atlantic Ocean to the Indian Ocean all the way to the tip of Africa," said virologist Preston Marx of the Tulane National Primate Research Centre and a co-leader of the research.
Ancient origins confirmed by DNA samples
"It would take many, many thousands of years to spread that far and couldn't have happened in a couple of hundred years."
Marx tested his theory that SIV had ancient origins by seeking out DNA samples from monkey populations that had been isolated for thousands of years.
The researchers found four different strains of SIV that were genetically divergent from those found on the mainland.
Slower mutation than thought
They compared DNA sequences of the viruses with the assumption that they were tracking how both evolved over 10,000 years.
The computer modelling showed the rate of mutation to be much slower than previously thought, indicating that virus is between 32,000 and 75,000 years old to have evolved to its current state.
These dates set a new minimum age for SIV, although it is likely to be even older, Marx says.
