Pity the poor Neanderthals, our prehistoric cousins. The first Neanderthal fossils were discovered in a place of that name in Germany in 1856. Archaeologists have since turned up fossils ranging from Protoneanderthals and Transition Neanderthals to Classic Neanderthals at about 75 sites from Western Europe to Central Asia. In examining the recovered fossils, tools, and other remains, archaeologists have attempted to reconstruct the lives, habitats, and habits of these archaic humans. Since all living non-Africans share, on average, 2.5 percent Neanderthal DNA, the question of their relationship to modern humans has fascinated scholars and the public alike.
There have been two theories concerning the disappearance of Neanderthals from the archaeological record about 30,000 years ago. One ascribes a primary role to the effects of radical and wildly fluctuating temperatures during a climate phase known as Oxygen Isotope Stage 3 (OIS3) on the environment and, thus, on the lives of Neanderthals. A climate downturn from 40,000 years ago coincides with their decline. Since Neanderthals had already lived in Eurasia for up to 200,000 years, during which time they had experienced and adapted to many glacial cycles, we are talking about really extreme weather, the likes of which Earth has not again experienced.
Modern humans moved out of Africa and into Europe about 40,000 years ago, during OIS3. Thus, Homo sapiens plays a major role in the second theory, which posits that the short, stocky, barrel-chested Neanderthals were forced to compete for woolly mammoths and cave bears with the more agile and leaner humans, who also carried assault weapons in the form of spears and other projectiles. Human-mediated extinction is the premise of The Invaders, with a twist. As the hyperbolic title proclaims, it was the “invading” humans and their dogs that did in the Neanderthals. Homo sapiens, Pat Shipman writes, is “unquestionably predatory.” We are in the territory of Elizabeth Kolbert’s recent Sixth Extinction (2014).
In this paleo-anthropological approach, Shipman, a retired professor of anthropology, marshals a benumbing amount of research on radiocarbon dating of fossils, chronology, genome sequencing, isotope stages, and such subjects as intraguild competition (“competitive exclusion”) and canid domestication. (This book is not for the fainthearted, and it is much in need of tables and graphs.) Shipman discusses what these new investigative techniques reveal about Neanderthal demise. She concedes, for instance, that “the severe bout of climatic deterioration” that began occurring about 45,000 years ago and that wiped out much of the vegetation behind which Neanderthals carried out their hunting gave the newly arrived humans and their projectiles a “substantial edge.”
She draws support for the human-mediated theory from the current field of “invasive biology,” which studies the effects of introducing species into (or removing species from) an ecosystem. In an ecosystem, there is invariably an “apex consumer” whose predatory habits keep the food hierarchy in circulation, while invasive species, as Shipman writes, disturb the balance and are “a major contributing factor in many and possibly most extinctions.”
Her proxy evidence for the effect of a new “apex predator” within an ecosystem, and thus for the disappearance of Neanderthals, is contained in her chapter on Yellowstone National Park. Before Yellowstone’s designation as a national park in 1872, most of the indigenous tribal peoples had been driven off the land. The incoming white humans eliminated their chief remaining rival, wolves, according to a policy endorsed by ranchers and the federal government. The removal of wolves, however, led to an overabundance of elk, which, in turn, caused degradation to rangeland. The number of coyotes also soared, since they were freed from suppression by their main competitors for prey. In the mid-1990s, 31 gray wolves from two Canadian parks were “released into [Yellowstone] to restore the natural balance of the original ecosystem before settlement by people of mostly European ancestry.” Elk numbers fell, while coyotes were immediately killed and driven away by the wolves, improving (among other things) “the survival rate of fawns of pronghorn antelope considerably.”
I am a layperson, but it strikes me as specious to compare the Yellowstone ecological “event”—which took place within a little more than a century and, moreover, was orchestrated by humans—with events that occurred over a time span of millennia and that cannot be directly observed.