Overview:
Everyone agrees that the human immunodeficiency virus (HIV) is a mutation or adaption of the simian immunodeficiency virus (SIV).  How the transfer occurred is up for debate.  One theory is that SIV was transferred to humans by a hunter getting monkey blood in a cut while butchering a monkey or through other human contact with monkeys.  This theory is called the Natural Transfer Theory.

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Lesson 17 – Natural Transfer Theory (Grayscale)
Lesson 17 – Natural Transfer Theory (Color)
Lesson 17 – Natural Transfer Theory (Color Ink Saving)

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