Some researchers in Denmark have released a map of what global mammalian megafauna distribution would be like if humans hadn’t existed. Spoiler Alert: There would be a lot more big mammals everywhere. I don’t think this is a surprise to anyone who has paid any attention to species that have gone extinct but which human ancestors dealt with (I think the problem is that everyone conflates “extinct” into one period, from the dinosaurs to the dodo bird), but this is the first time that I know of that it has been quantified and displayed in an easy-to-understand graphic. Here’s the map:
I’ve often argued that the reason there are still so many large mammals in Africa is because they evolved with humans, and everywhere else they evolved without humans – invasive species tend to mess things up. The authors agree with me, and go further to say that many of our ideas about diversity are wrong. For example:
Today, there is a particularly large number of mammal species in mountainous areas. This is often interpreted as a consequence of environmental variation, where different species have evolved in deep valleys and high mountains. According to the new study, however, this trend is much weaker when the natural patterns are considered.
“The current high level of biodiversity in mountainous areas is partly due to the fact that the mountains have acted as a refuge for species in relation to hunting and habitat destruction, rather than being a purely natural pattern. An example in Europe is the brown bear, which now virtually only live in mountainous regions because it has been exterminated from the more accessible and most often more densely populated lowland areas,” explains Soren Faurby.
I found the press release through IFLS, and Josh Davis writes at the bottom:
The study does, however, presume that the changing climate at the end of the Pleistocene was not sufficient to kill the large mammals off on its own, and that it was man’s influence that delivered the death blow. This area of research is hotly debated and contested, with arguments flying back and forth as to the real reason the world’s large mammals died out. It’s generally thought likely to be a combination of climate change and hunting, but it’s impossible to say whether or not all species of mammal would have been able to adapt sufficiently to a changing environment and survive to present.
I can’t help but think arguments against human causes are simply trying to avoid guilt. Let’s look at Australia: The continent had a vast diversity of mammalian megafauna for tens of millions of years, megafauna that survived ice ages and warm times, and – most relevant – several glaciation events within the current ice age. Along come humans, and during the very next glaciation event that happens many, many species become extinct. The significant difference was the introduction of humans. Sure, it’s “impossible” to say whether all species of mammals would have been able to adapt, but it’s a pretty safe bet that most of them would have, because they had before.