Once and Future Giants

Who Should Read It

Everyone with any interest in the megafauna of our last Ice Age.

Why Should We Read It

This books is an in-depth and the definitive source for discussing what we know about the woolly mammoths and other such megafauna, and why this knowledge matters today.

What Will We Learn

We will understand not only how the megafauna shaped our prehistoric world, but also come to understand the implications of what their absence means to our planet today and in the near future.

Book Reflections

The definitive book on the megafauna of the last Ice Age!

I have been interested in the megafauna of the Pleistocene Epoch (AKA, the wooly mammoths and saber tooth tigers from our last "Ice Age") ever since serendipitously coming across Ben Mezrich’s Woolly at an airport. While that book was an entertaining introduction into the genre of "creative nonfiction", reading Woolly was a dissatisfying method of learning about these extinct animals. I had greater hope for Yuval Noah Harari's Sapiens: A Brief History of Humankind. In the context of general nonfiction best sellers published in the last two years, Sapiens is certainly essential reading. For my purposes of self-education in Pleistocene wildlife, I should have judged Mr. Harari's book by its cover. Why expect a book about woolly mammoths when the title clearly states it is about human beings? In the end, the most definitive book I found on this topic was also accidentally discovered (in a used bookstore this time): Sharon Levy's Once and Future Giants.

The evidence is damning: humans probably significantly contributed to the megafauna's extinction.

North America during the Pleistocene Epoch once supported mammals of massive size, including mammoths, camels, and lions. Prior to the 1960's, most archeologists attributed their extinction solely to the global changes in climate that marked the end of the last Ice Age approximately ten thousand years ago. The problem with this long-standing hypothesis was that a growing body of scientific evidence (for example, archeological pollen studies) indicated that these megafauna had outlasted multiple cycles of global warming and cooling. From the perspective of climate change over geologic time, the rise of average global temperatures at the end of the last Ice Age was not particularly severe or remarkable. There must have been another decisive factor contributing to their demise: human beings. The evidence against our species is damning: across the globe, evidence of the earliest known human settlements tend to coincide with archeological findings of the last known surviving megafauna of that region. Most archeologists now support that the Pleistocene megafauna in North America died from a combination of human hunting and global warming.

In Pleistocene Australia, the climate change that killed the megafauna were probably the human-initiated wildfires.

To best illustrate the impact of the human species, we travel to Australia. This continent's Pleistocene fossils tell a nuanced tale of ecological disaster that involved more than just extinction via hunting. Australia is a dry continent, and many of its native trees have evolved around the lightning wildfires that cyclically occur every 20-50 years. In pre-human Australia, these trees fed giant herbivore kangaroos and rhinos, who in turn fell prey to giant lizards and marsupial lions (just to name a few megafauna). The prehistoric landscape was therefore probably a dynamic flux of woodland forest and savannah grass, which changed depending on whether the giants trampled in that area, and when and where lightning struck in any given 20-50 year period. When the first Aboriginal Australians arrived, this entire ecosystem strained not only under their hunting pressure, but also from their agricultural practice of cultural burning. These yearly, human-initiated wildfires were an ecologically unprecedented phenomenon (100 wildfires per century, compared to 2-5 wildfires per century in the pre-human era) from which the woodlands, and eventually the continent's megafauna, had no chance to recover from. Climate change probably killed off the world's megafauna; in Australia, that climate change might have been the work of humans themselves.

"In an ironic twist of fate, Australia's most ecologically diverse areas today are found in areas in which Aboriginal burning traditions are still actively practiced."

Our role as the doomsday harbinger is still only a small portion of the ongoing story of Australia's ecology. In an ironic twist of fate, Australia's most ecologically diverse areas today are found in areas in which Aboriginal burning traditions are still actively practiced. The fires from these burning traditions are never as widespread or as hot as a blaze from a modern-day lightning strike on flammable vegetation (overgrown and uncleared in the absence of megafauna). These controlled fires provide a more nurturing environment for Australia's native plants to grow, which then support an array of herbivores and carnivores. It seems, then, that while prehistoric humans might have killed off the Pleistocene megafauna, the Aboriginal Australian descendants found a way to assume the ecological niche left vacant by the mass extinctions. In other words, Australia as the Europeans discovered it in the 1600's was not in a "natural" or "pristine" state. By that time, Australia had already been a man-made ecosystem for thousands of years.

"'...it is our current world without megafauna that is the unprecedented unnatural state of life."

If we use Australia as a case study, we realize that we probably did kill off the megafauna, and we will lose much more if we cannot correct this error. To that end, ecologists are working to "re-wild" animals back to their traditional natural ranges. The re-wilding of wolves in Yellowstone National Park, for example, enabled better control of the elk population and subsequent stabilization of the grizzlies and cougar population. Some scientists want to push the envelope further, and introduce African camels and elephants into the American wild to replace the extinct American camel and mammoth. Others dream even bigger, and work to make the mammoths "de-extinct." No matter what their perspective, all these scientists agree on one thing: our collective human history only knows of a world without megafauna, and we tend to assume that this world without giants is the natural order of life. We probably have it all wrong, and it is our current world without megafauna that is the unprecedented unnatural state of life.