How long have humans inhabited the earth?
Thanks!
-alison

100 of billion of years

Present day species of humans... homo sapiens sapeins have seemed to emerged around 25000 yrs ago. Though our earliest, man like ancestors like australopithecus were existing 5 million yrs ago

Hello,
Actually, the oldest fossils of anatomically modern Homo Sapiens have been found in Africa, and were dated to be about 130,000 years old.

The earliest pre-humans date back to about 4.5 million years ago.

Check out the Smithsonian site for more information, it is quite interesting:

http://www.mnh.si.edu/anthro/humanorigins/ha/a_tree.html

Mark