Some scientists are making the point that we have entered a new epoch, and have left the Holocene because of new factors that only appeared in this new age. I agree with them. http://www.globalpost.com/article/67...n-impact-study
It could be a relatively short epoch, with the sixth extinction well underway. Instead of a layer of iridium, future geologists will be unearthing a layer of plastic.
If it's true, I don't think we can easily get out of it. Authors seems to want to say we have have to get out of it, but approaching 10-bil pop I am not sure that is a reasonable expectation.
Anthropocene is a geological epoch because things that could be dug up later are distinct from earlier epochs. This will almost certainly be the case, although it is not obvious that plastics will persist through geological time (except in landfills?). Concrete and refined metals seem like more durable markers. To the extent it's controversial, it centers on when to declare the transition and that depends on one's choice of markers. But that humans now have dominant effects on chemical, hydrological and other planetary cycles is not controversial. Not among readers of the scientific literature. There is no evidence that any other single species has ever come close. We should not mix up epochs and global extinctions. To be sure, there is evidence that we are now (or soon to be) in 6th. This remains unresolved. It is possible that a single dominant species (guess who?) could manage even with the loss of many rare species. This remains unresolved
article in press: J. Zalasiewicz, et al., The geological cycle of plastics and their use as a stratigraphic indicator of the Anthropocene, Anthropocene (2016), http://dx.doi.org/10.1016/j.ancene.2016.01.002
Plastics, concrete, and several other 'novel' sediments. The 'functionally' part with drag us into the Environmental topic, be warned. The Anthropocene is functionally and stratigraphically distinct from the Holocene Colin N. Waters, et al. Science 351, (2016); DOI: 10.1126/science.aad2622
How the anthropocene started is clear enough. It's what is buried above that layer that will be very interesting (not including me).
The Romans didn't expand their roads globally. They didn't even get to all of Europe. When places got too cold for olives, they tended to lose interest.
For what it's worth (not much) I actually favor declaring based on the earliest 'clearly human' change in sedimentary deposits. Humans piled up rocks in novel ways, much increased amounts of (forest fire) charcoal and the crop thing changed pollen records in wetland sediments. All, in more or less global ways. Later, changes were larger and more varied. But I am inclined to view 'Energy-cene' as a logical extension of 'Agriculture-cene', already previously underway.
