How Long Have Humans Dominated the Planet?

A call goes out for a new global effort to puzzle out humanity's ecological history over the last 50,000 years or more

David Biello

Source - http://www.scientificamerican.com/article.cfm?id=length-of-human-domination

Image: NASA

Want to know when the Anthropocene started exactly? It will only cost an entirely revamped scientific effort in archaeology, ecology and paleontology, among other disciplines, at an unprecedented planetary scale, according to a new paper calling for such a scheme.

The putative start date for what scientists have begun to call the Anthropocene—a newly defined epoch in which humanity is the dominant force on the planet—ranges widely. Some argue that humans began changing the global environment about 50,000 years back, in the Pleistocene epoch, helping along if not outright causing the mass extinctions of megafauna, from mammoths to giant kangaroos, on most continents. Others date it to the emergence of agriculture some 7,000 years ago. The most definitive cases to be made coincide with the start of the industrial revolution and the dawn of the atomic age. The beginnings of burning fossil fuels to power machines in the 19th century initiated a change in the mix of atmospheric gases , and the first nuclear weapon test on July 16, 1945, spread unique isotopes across the globe.

There is little doubt from the archaeological record that humans have been altering ecosystems on a local scale for at least 50,000 years if not longer, but the extent of that alteration remains unknown. Recent work by ecologist Erle Ellis of the University of Maryland, Baltimore County, and others suggests that for at least 3,000 years hunting, farming and burning have shaped most landscapes on the planet, based on computer models.

To definitively prove that with field evidence would require the kind of archaeological and ecological effort the world has never seen, a scheme Ellis and co-authors lay out in a paper in the inaugural issue of the new open-access journal Elementa, devoted to the Anthropocene. That plan, they say, would have to be global in scale—to eliminate the bias in current research toward the most accessible archaeological sites—as well as unusually open. Few scientific disciplines are as secretive as archaeology, paleontology and paleoecology, given that careers are made (or not) based on access to specimens.

The payoff would be a true historical baseline for what is "natural" for the first time, complementing efforts like the Long Term Ecological Research Network and the new National Ecological Observatory Network, among others. "What is a natural system has a cultural history as part of its constitution," says archaeologist Dorian Fuller of University College London, a co-author of the paper and a supporter of "Big Archaeology," who notes that the ecosystems of Amazonia, Europe and even the western U.S. are all products of at least millennia of human activity.

Prospects for such a global effort are, admittedly, dim, not least because it is unclear who would fund such work. But a global, synthetic effort is the only way to answer the question: How long have humans been terraforming? "This is great scientific work that can be done and needs to be done," Ellis argues. "It will help us define the role of humans in shaping the Anthropocene and will mark a scientific triumph for humanity: a full empirical account of our rise to global stewardship of the biosphere."