Humans have had a considerable impact on the earth in the last hundred years but recent research indicates that humans may have caused substantial alteration to the biospheres starting around 5,000 years ago when the total human population was around 50 to 100 million.
Rowan, Andrew N.
"The Human Footprint from the Last Ice Age to the Present,"
WellBeing News: Vol. 3
, Article 2.
Available at: https://www.wellbeingintlstudiesrepository.org/wbn/vol3/iss5/2