humans, megafauna, and the frequency of fires -- 12/12/18

Today's selection -- from Origin Story by David Christian. Humans, megafauna, and the frequency of fires:

"The first humans in Australia found many species of large animals, or megafauna. Some were as big as the rhinoceroses, elephants, and giraffes of South Africa, the one part of the world in which large numbers of megafauna survive today. In Australia, there were giant kangaroos and wombats and huge flightless birds such as Genyornis newtoni. Then, quite suddenly, most of the Australian megafauna disappeared, as they would eventually disappear in Siberia and the Americas.

"Perhaps they disappeared because climates changed. But they had survived previous ice ages, so it is hard not to think that humans, with their increasingly sophisticated hunting meth­ods, may have tipped them over the edge. The chronology sup­ports this explanation. In Australia, Siberia, and North America, the megafauna vanished not long after the arrival of humans. Perhaps, like the dodo in Mauritius, the megafauna didn't fear our ancestors enough, unlike African megafauna, which had coevolved with humans and knew how dangerous we could be. In any case, megafauna, like all large animals (including the dinosaurs), are particularly vulnerable to sudden changes. There are many modern examples of megafaunal extinctions, such as the disappearance of the large New Zealand birds known as moas within a few centuries of the arrival of humans. In Siberia and the Americas, we even have direct evidence of kill sites, so we know that humans hunted megafauna such as mammoths.

Visual representation of the history of life on Earth as a spiral

"Removing megafauna changed landscapes. Large herbi­vores can chomp their way through a lot of plants. Eliminating them increased the frequency of fires, as plant remains were left uneaten. In Australia about forty thousand years ago, the num­ber of fires increased in many regions. A large percentage may have been started by lightning strikes. But we know that here, as in many other parts of the Paleolithic world, humans used fire systematically to fertilize the land. These technologies are known to archaeologists as fire-stick farming, after the fire sticks that indigenous Australians carried to fire the land in historical times.

"Systematic use of fire, not just to cook or protect yourself but to transform your environment, represents one of the first signs of the growing ecological power of our species. If you had the skills needed to manage fires safely, regular firing of the land provided many advantages. Burn an area of grassland, then wander back in a day or two, and the first thing you will find is plant and animal barbecues. Wait a few weeks and you will find new growth, because the fire has scattered ash as a fertilizer and sped up the decomposition of plant and animal remains. Grasses and other plants will sprout and can be har­vested sooner. And new plants will usually attract herbivores and small reptiles, making the hunting easier and more productive. In short, fire-stick farming increases the productivity of the land."



David Christian


Origin Story: A Big History of Everything


Little, Brown and Company


Copyright 2018 by David Christian


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