A team of geologists say that, in just two centuries, stunning population growth, sprawling megacities and increased use of fossil fuels have wrought such vast and unprecedented changes to our world that humans actually might be ushering in a new geological time interval they have dubbed the "Anthropocene Epoch".

Writing in Environmental Science and Technology, the team says the dawning of this new epoch may include the sixth largest mass extinction in Earth's history.

First proposed by Paul Crutzen from the Max-Planck-Institute for Chemistry more than a decade ago, the term "Anthropocene" has provoked controversy. However, as more potential consequences of human activity — such as global climate change and sharp increases in plant and animal extinctions — have emerged, Crutzen's term has gained support.

Currently, the worldwide geological community is formally considering whether the Anthropocene should join the Jurassic, Cambrian and other more familiar units on the Geological Time Scale.

The scientists note that getting that formal designation will likely be contentious. But they conclude, "However these debates will unfold, the Anthropocene represents a new phase in the history of both humankind and of the Earth, when natural forces and human forces became intertwined, so that the fate of one determines the fate of the other. Geologically, this is a remarkable episode in the history of this planet."

J. Zalasiewicz et al., 'The new world of the Anthropocene. Environ. Sci. Technol., 2010, 44 (7). doi:10.1021/es903118j