The Keystone Species

 

"The Archeology of Global Change: The Impact of Humans on Their Environment" is a book published in 2004 by the Smithsonian Institution. Yes, folks, it´s time for the Ashtar Command to bash the myth of the noble savage again! So far, I´ve "only" read the first part of the volume, which contains a somewhat eclectic blend of articles about Polynesia, the US Southwest and the Pacific Northwest. 

Humans have never lived in fundamental "harmony" with Nature, nor have they been "natural conservationists". The first evidence for overexploitation of natural resources comes from "archaic Homo sapiens". The size of tortoise shells and shellfish gradually decrease with time at Neanderthal sites around the Mediterranean, suggesting that our evolutionary siblings gathered (and consumed) the larger species or varieties first, making them go extinct! This also confirms the "optimum foraging" model, according to which humans should always harvest the most nutritious and easily accesible specimens first, and only then proceed to smaller, less nutritious and/or less accesible individuals. This pattern shows up again and again in the archeological record. In plain English, if forced to chose between eating and cultural ideology, most humans most of the time chose to eat. 

The contributors to this volume believe that humans were also responsible for the Pleistocene extinctions of "charismatic megafauna" in Eurasia, Australia and the Americas. I admit that I have no idea whodunnit, and the issue is only mentioned in passing, but some suggestive facts could be cited. For instance, that only a few species of megafauna went extinct in Africa, where humans and other animals presumably co-evolved for millions of years. By contrast, most megafaunal species went extinct in Australia and the Americas, where humans arrived comparatively late, and the animals hadn´t evolved any defenses against human predation. However, this assumes that received paleontological wisdom about human migrations is correct. What if humans arrived much earlier? An alternative hypothesis is that the megafauna went extinct due to climate change at the end of the Pleistocene. Of course, none of this has any impact on the conclusions of this book, which deals mostly with the Holocene (the present time period).

Patrick V Kirch´s article "Oceanic Islands: Microcosms of `Global Change´" deals with human impact on two Polynesian islands (Easter Island and Mangaia) and one ditto archipelago (Hawaii). The humans in question are the "Natives", the Polynesians, who colonized the islands long before the arrival of White Europeans or Americans. If pre-modern "Natives" are natural conservationists, islands should still be teeming with endemics (including flightless birds) and in general have the same biotopes as before colonization (except in cases of severe climate change). Unless, of course, evil Whites upset the balance! In reality, the Polynesians radically altered the island environments they encountered during their migrations in the Pacific. Nor is this surprising: the Polynesians practiced slash-and-burn agriculture and irrigation, introduced new food crops, and carried with them dogs, pigs and chicken. They were also followed by invasive species such as the Pacific rat or garden snails. And yes, they did hunt the animals already living on the islands...

Easter Island (Rapanui) was originally covered by parklandlike forests, with a canopy of palm trees. About 25 different species of seabird nested on the island. Rapanui was in effect a gigantic seabird rookery. There were also seven species of endemic landbirds. After 1,500 years of human habitation, Easter Island had changed completely: the forests had been cut down and replaced by grassland, the endemics were extinct, and most seabird species left the island, only a few remaining at small islets that are virtually unaccesible to humans. The Natives were fighting constant wars, which may have included cannibalism. 

The story of Mangaia (one of the Cook Islands) is similar. Probably colonized by Polynesians about 2000 years ago, the island´s environment had completely changed about 400 years ago. The interior of the island is covered by pyrophytic ferns and other fire-resistant plants, presumably in response to slash-and-burn agriculture. Of 17 documented landbird taxa in the archeological record, only four remained 600 years later. Some seabird species also left the island. Fish and gastropods found at archeological sites became progressively smaller over time, suggesting heavy exploitation of these particular resources. Mangaian society developed in a way similar to Rapanui, with constant tribal wars, widespread cannibalism, human sacrifice, and so on. (I won´t bother you with Hawaii.) 

The most fascinating contribution in the first section is titled "Revising the `Wild´ West: Big Game Meets the Ultimate Keystone Species" by Paul S Martin and Christine R Szuter. It meticulously analyzes the journals of the famous Lewis and Clark Expedition (1803-1806) to Montana and the Pacific Northwest. In Montana, the expedition encountered enormous flocks of bison and other game animals, one bison flock estimated to be 10,000 animals strong! The bison, elk, wolves and grizzly bears were also extremely tame. Clark managed to kill a wolf with his spontoon, suggesting that he managed to get very close to it (a spontoon is apparently a weapon about 2 meters long). The wolf was eating a drowned bison and seems not to have cared much about the human hunter, before it was too late! Lewis, Clark and their "Corps of Discovery" had no problem finding and killing animals for food east of the Rocky Mountains. West of the Rockies was a different story. There, game was virtually non-existent. At first, the expedition was forced to live on dried fish and roots provided by the Natives, something that made them sick. Later, they bought horses and dogs from various Native groups, with the intention of killing and eating them. Nor were the animals in the Pacific Northwest particularly docile. Killing a grizzly was considered an extremely heroic and manly act by the Natives, since these animals were so extremely aggressive. 

What could account for the peculiar difference between the two areas explored by the Lewis and Clark expedition? The two explorers themselves had no explanation, and many historians don´t give one either. However, the answer is right there, in the journals.

It´s the Natives, stupid.

The Native population was abundant *west* of the Rockies, where the game was most scarce. This would indeed suggest some kind of connection. The situation in Montana was more complex. An aggressive Native group known as the Blackfoot had virtually cleansed large areas of competing tribes by systematic attacks. Thus, the overall population density of Montana was probably lower than the areas further west. Of course, Blackfoot raiding had led other tribes to take defensive measures. Vast stretches of "no mans land" separated the various tribal territories from each other. In these areas, hunting was deemed difficult, due to the risk of being spotted and killed by scouts from the enemy tribe. Martin and Szuter believe that the abundant wildlife described by Lewis and Clark lived in these "DMZs". There is some later evidence for the same phenomenon, for instance Colorado circa 1820-1840, when the bison disappeared from the territory *when the Indian tribes made peace with one another*. A more recent example would be the border between North and South Korea, where wildlife is thriving.

These facts (plus the later disappearence of many Native groups) make it problematic to argue that current conservation efforts are about "restoring" an original, pristine wilderness. There simply isn´t such a thing. There hasn´t been a pristine wilderness sensu stricto since humans first arrived in North America 12,000 years ago. Animal numbers have been controlled by humans ever since. Humans are "the ultimate keystone species". The "balance" (if that´s the right word for it) between Native hunters and prey animals was disturbed when Natives aquired horses, but also when European diseases severly decimated the Native population. This led to all kinds of anomalous situations, often misreported as some kind of "Eden" where animals are super-abundant and tame. Something that is really the result of an atypical absence of human hunters, something seldom seen since the Pleistocene...

I will certainly continue reading this book with considerable interest.