III.

Biological Activity

Animals and plants have not evolved much during the Holocene Epoch. Most extinctions in the Holocene are the result of human interference. The retreat of the Pleistocene glaciers caused significant shifts in the areas that animals and plants occupied. In the earliest part of the Holocene Epoch, species re-colonized the recently uncovered land. As the climate warmed, some animal and plant species became separated from other populations. In some cases species thrived in their new habitats and in some cases they did not. Human hunting practices and new diseases carried by humans and other new animals probably made a difference in whether some of these species, particularly many of the large North American late Pleistocene mammals such as mastodons and saber-toothed tigers, became extinct.

Later in the Holocene and particularly in Europe, the Middle East, and parts of Asia, humans were responsible for great modifications in natural vegetation and changing animal ranges. This pattern of interference has become particularly pronounced in the last few hundred years as human numbers have grown. Human interference with natural systems has caused, and will continue to cause, many extinctions in both the animal and plant kingdoms. Some scientists suggest that this part of the Holocene will mark another major extinction event in the geologic record of the earth.