HIV gradually destroy the immune system by attacking and killing a type of white blood cell called a CD4 cell. CD4 cells play a major role in protecting the body from infection.
HIV cannot grow or reproduce on its own. Instead, the virus attaches itself to a T-helper cell and fuses with it. It then takes control of the cell's DNA, replicates itself inside the cell, and finally releases more HIV into the blood – continuing the multiplication process. This is the HIV lifecycle.
They evolved because of spoken language and tool use.
*This hypothesis suggests that increased language and tool use increased selection for the capacity to reason and communicate, which favored large brains.
