A rather profound bias running through much ecological thought holds that primitive people like hunter-gathers live in “harmony” with the environment and, unlike civilized people, seldom if ever cause significant ecological harm or extinctions. I think this study reported by National Geographic falls into this category. It purports to show that the extinction of macroform mammals like mammoths, camels and horses in North America at the end of the last ice age resulted from climate change and not human predation.
I don’t buy it for several reasons.
The major problem with all arguments about extinctions driven by the end of the ice age climate is that they don’t explain why so many species went extinct at the end of the last ice age (about 10,000 years ago) when they had survived numerous ice ages in the past.
The average mammalian species has a “lifespan” of around 10 million years. Most of the species and sub-species that the study concerns survived for at least 1 million years. Ice ages, however, occur in periods of tens of thousands of years. All the species that suddenly went extinct at the end of the last ice age had survived through at least four or five previous ice ages as well as the warmer intervals in between. The end of the last ice age also doesn’t seem to have been unusual in any way. So we see a pattern where many large species survived numerous cycles of extreme climate change, all to suddenly drop dead at the end of the last age, when modern humans (who evolved about 50,000 years ago in the middle of the last glacial period) suddenly spread into the formerly frozen lands.
You don’t have to be Agatha Christie to figure this one out.
Humans have a profound impact on many species because we hunt in a fundamentally different manner than any other predator. Size is a defense against predators that rely on fang and claw because such attacks have very little penetrating power. They rely on raking, pinning and suffocation to kill. Something as large as a mammoth is nearly immune to such attacks. Modern humans, however, kill or cripple by poking small but deep holes with tools. The pygmies of Africa used to routinely hunt elephants by sneaking up on them in the brush and poking them in the jugular with a sharp stick. They would then just follow the elephant around until it keeled over from blood loss. It is actually easier and more cost effective for humans to hunt large prey than it is for them to hunt small prey. It takes a whole lot of rabbits to add up to one mammoth.
The end of the last ice age saw a sudden drop off in the average size of mammalian species. The giants we see in museums are not just the outliers of millions of years but represent long-term norms. When humans appeared on the scene, especially modern humans with the language skills to coordinate attacks on large animals, size ceased to be a protection. Species shrank or died out. Even species like deer, elk and moose are smaller now than they were 10,000+ years ago. Species resisted human predation by becoming smaller individual targets. Only in sub-sahara Africa, where animals had lived with humans for millions of years, did macroform mammals survive and even those are smaller than their ancestors.
There is nothing mystical about the relationship between pre-civilization peoples and the environment. They show no more awareness of the multi-generational consequences of their actions than do civilized people. In fact, arguably they show less because they have little long term cultural memory. They can’t actually see the consequences of their actions repeated over the course of hundreds of years.
It’s really time for this overly romantic view of hunter-gatherers to go the way of the mammoths.