If someone with HIV is diagnosed with one of these opportunistic infections (even if the CD4 count is above 200), he or she is said to have AIDS. AIDS usually takes time to develop from the time a person acquires HIV--usually between 2 to 10 years or more.
It has been thought that the wheel was invented in 8000 B.C but the oldest discovered wheel dates back to 3500 B.c. It was discovered in Mesopotamia (nowadays in Iraq). Below are the timelines of wheels and its usage in different era.
One of the reasons why the wheel was invented only at this point in history is due to the fact that metal tools were needed to chisel fine-fitted holes and axles. This leads to the next reason â the wheel was not just a cylinder rolling on its edge.