Comments

I have not read the Nature article, but this is most likely a DNA study. What they can do is compare the latest strains to those collected since it's public discovery in the late 70's and early 80's and now this one from the 1960's. This way they can plot what area's of it's genome have been changing and extrapolate that to it's first virulent strain. Recall how the bird flu was first killing many birds, but then over time was spreading to humans in close contact. This is because certain parts of the virus changed making it possible for it to infect humans. It's statistics. # infected 100,000,000'...............................................* 10,000,000 '..............................................*. 1,000,000 '.............................................*.. 100,000 '...........................................*.... 10,000 '.........................................*...... 1,000 '.......................................*........ 100 '....................................*........... 10 '................................*............... 1 '*............................................... 0 ''''''''''''''''''''''''''''''''''''''''''''''''' Year 1884 1960 1980 2008 It's tough to make an exponential graph out of periods, but you get the idea. It's all about observing the number of known cases over the years and extrapolating when it started. It gets more complicated when you get into the actual DNA explanation. This has to do with phylogeny, or looking at other virus that are similar in DNA structure on specific regions of the HIV genome. These other strains are thought to be where the HIV strain originated from. The abstract online says that this 1960's strain gives more evidence that it is a relative to a particular type of monkey AIDS.