“We compute those baselines for mammals of temperate North America, using a sampling-standardized rich fossil record to reconstruct species-area relationships for a series of time slices ranging from 30 million to 500 years ago. We show that shortly after humans first arrived in North America, mammalian diversity dropped to become at least 15%–42% too low compared to the “normal” diversity baseline that had existed for millions of years. While the Holocene reduction in North American mammal diversity has long been recognized qualitatively, our results provide a quantitative measure that clarifies how significant the diversity reduction actually was.”

“Our results provide a quantitative assessment of what has long been primarily a qualitative observation: namely, the decline in mammal diversity that occurred as human presence first began to dominate the North American landscape. We demonstrate that this decline represented a 15–42% loss (depending on biogeographic province) in mammal species richness. Therefore, the diversity baseline we are at today already is well below the “normal” biodiversity baseline for North American mammals, if we define “normal” as the condition that prevailed through most of the millions of years modern mammal families have been on Earth.”

Carrasco MA, Barnosky AD, Graham RW (2009) Quantifying the Extent of North American Mammal Extinction Relative to the Pre-Anthropogenic Baseline. PLoS ONE 4(12): e8331
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0008331

Never accuse someone of a failing when arguing from a position of ignorance, Scout. It just makes you look churlish. My position on the staff of a University gives me access to the world’s literature, and it just does not tally with all aspects of your world view.

Just take one article from that world literature, which charts Pleistocene climate change as a way of differentiating human impacts from other drivers of ecological change. 90% of Australia’s large mammals were extinct by around 45 ka. An analysis of faunal data from the Naracoorte Caves in southeastern Australia shows that, despite significant population fluctuations driven by glacial-interglacial cycling, the species composition of the mammal fauna was essentially stable for 500 k.y. before the late Pleistocene extinctions. Larger species declined during a drier interval between 270 and 220 ka, likely reflecting range contractions away from Naracoorte, but they then recovered locally, persisting well into the late Pleistocene. Because the speleothem record and prior faunal response imply that local conditions should have been favorable for megafauna until at least 30 ka, climate change is unlikely to have been the principal cause of the extinctions.

(Mammalian responses to Pleistocene climate change in southeastern Australia, Gavin J. Prideaux, Richard G. Roberts, Dirk Megirian, Kira E. Westaway, John C. Hellstrom and Jon M. Olley, Geology 2007;35;33-36)

Megafaunal carnage throughout the world’s history correlates with the arrival of modern man, from the 40-50,000 years ago in Australia, the 13,000 years ago in the Americas, to the more recent oceanic explorations that saw the arrival 2000 years ago in Madagascar and 1000 years ago in New Zealand. In the Americas, as in New Zealand and Australia, the extinction of species was only compounded by the arrival of Euro-settlers and their agriculture.

Open some space in your mind, Scout. You can’t just pick and choose what suits your thesis – as is the case with your conibear traps.

You said:
“Why is it necessary to assume anything good about the relative impact of HGs other than they got by, probably as gathers first before they became hunters and before dispersal saw modern humans occupy many land continents, extinguishing the megafauna as they went.”

Firstly, this depends on your definition of “good”. If you think not destroying the landbase is “good” than we are on the same page. Secondly, it is not an “assumption” that hunter-gatherers tended the land in a way that created more biodiversity, it is based on notable observations and recreations. Thirdly, the megafauna extinction was not the cause of hunter-gatherers, that theory has been debunked for a while now due to scientists further understanding of climate change impacts and how hunter-gatherers manipulate the environment. Fourthly, every animal tends its food supply in a way that keeps its food alive. If this were not the case, every animal would exhaust its food supply very quickly. There are ways of killing that promote growth.

You said:
“The little we can do now is honour that human free wilderness the best we can, while recognising that there are contemporary ways that humans could live in modified wilderness if they massively tempered their domination of it.”

This ignores the mounting data on how hunter-gatherer land management increase biodiversity (not necessarily biomass, but biodiversity). Wilderness is a myth. Even foragers greatly manipulate the land. They tend the wild. Squirrels plant oak forests. Beavers create wetlands and tend willows. Every animal changes their environment. Humans do this too. In the past we could assume that since people lived as hunter-gatherers for 3 million years or so, that they did so in a way that didn’t fuck up their environment (cause hey, here we are today right?). Now we don’t have to assume that, we actually have evidence that proves it.

Sounds like a beautiful book worthy of being pursued and to be shared with others.