Change in the Paleolithic Era

Change in the Paleolithic Era

Lecture 23

Today, we’re at the end of an interglacial that’s already lasted 10,000 years—and that’s something worth thinking about.

One of the reasons why history texts rarely discuss the Paleolithic era is that things changed so slowly that it is easy to think of this as an era in which nothing happened. Indeed, Paleolithic peoples themselves may have seen history as a cyclical pattern of seasonal and life changes within an essentially unchanging world. This is a view of history that Romanian historian of religion Mircea Eliade called the “Myth of the Eternal Return.” Yet, with the bene t of hindsight and with modern techniques for tracking and dating long-term changes, we can see that this view is illusory. At large scales, a lot happened in the Paleolithic era, so the astonishing adaptability of our species is already evident in the Paleolithic era. Though change was much slower than today (too slow to be observed by the people who lived through it), it was much faster than in any pre-human community.

This lecture will describe three main types of long-term change. First, we discuss the dramatic climatic and environmental changes associated with the ice ages. Second, we discuss the migrations that took Paleolithic humans to all parts of the Earth (except for Antarctica and the Paci c). Third, we describe the increasing impact of our Paleolithic ancestors on the natural environment.

The study of climate history has advanced rapidly in recent decades, driven partly by research into global warming. An example is the analysis of ratios of different oxygen isotopes in bubbles of air from ice cores. These ratios vary depending on the amounts of ice locked up in glaciers, so they can indicate changes in global temperatures.

Such techniques have revealed dramatic climatic changes. For 50 million years, global climates have slowly gotten cooler. This has reduced evaporation from the oceans and increased aridity. During the Pleistocene era (the last 2 million years), ice sheets spread in polar regions, generating

a series of ice ages. In the last million years, ice ages have normally lasted about 100,000 years, with warmer “interglacials” of about 10,000 years in between. Our species has already survived two ice ages. Today, we are at the end of an interglacial that has already lasted 10,000 years.

At the coldest phases, tundra-like steppes and deserts spread, forests retreated, glaciers covered much of North America and northern Eurasia, sea levels fell as water was locked up in glaciers, and plant growth was less vigorous in middle and upper latitudes. These changes may have shaped the evolution of our ancestors because, with their brains and their increasing ability to network, they were ideally suited to survive such rapid environmental changes. In summary, for most of the Paleolithic era, global climates were generally colder and more arid than today, though these differences were less marked in tropical regions than in higher latitudes.

The most striking historical change in the Paleolithic era was the migration of modern humans around the world. Humans were good at adapting to new environments because, through collective learning, they kept generating new technologies as they explored the environments at the edges of their home ranges. Until about 100,000 years ago, all humans lived in Africa. During this “African” era of human history, which includes at least half of human history, humans settled new environments within Africa, adapting to deserts, forests, and sea shores.

In the last 100,000 years, some humans left Africa. Entering southern Eurasia was not hard; indeed, other species (including ergaster) had made similar migrations. But migrating further a eld required more ingenuity. At the height of the last ice age, when sea levels were lower than today, Australia, Papua New Guinea, and Tasmania were joined in the single ice age continent known as “Sahul.” Humans rst entered Sahul about 50,000 years ago, from what is today the archipelago of Indonesia. Reaching Sahul required exceptional maritime skills, for migrants had to cross at least 40 miles of open water. When they arrived, they encountered completely unknown environments, animals, and plants. No other species had made this crossing successfully.

From 40,000 to 30,000 years ago, humans entered the tundra-like environments of ice age Ukraine, Russia, and Siberia. Plant life was less abundant here, so they had to learn to hunt large mammals such as mammoth, to tailor well- tting skin clothing, and to manage re. Sites from this era suggest how they lived. At Pushkari, in Ukraine, 19,000 years ago, where temperatures could fall to 30°C in winter, people lived in round houses built using mammoth bones. Though humans may have entered North America earlier, we know they crossed there from eastern Siberia by about 13,000 years ago.

By 13,000 years ago, the range of our species was already much wider than that of any other large mammal species, a clear sign that our remarkable ecological and technological prowess was already apparent in the Paleolithic era. These dates also suggest that the pace of innovation accelerated during the last 50,000 years. This is the archaeological reality behind the idea of an “Upper Paleolithic Revolution.”

As humans migrated, their numbers increased, and so did the number of archaeological remains they left behind. Though estimates of Paleolithic populations are largely guesswork, Italian demographer Massimo LiviBacci suggests there were several hundred thousand humans 30,000 years ago and 5 or 6 million humans at the end of the Paleolithic era, about 10,000 years ago.

The dominant form of change in the Paleolithic era can be described using the ugly word “extensi cation” (as opposed to “intensi cation”). By “extensi cation,” I mean technological change that allowed migration to new environments without permitting more intensive exploitation of existing territories. Extensi cation explains why the size and complexity of individual human communities did not increase during the Paleolithic era, though the total number of communities did increase.

As Paleolithic humans explored more environments and developed new techniques to deal with them, they began to have an increasing impact on their environments. Here are two striking examples. Humans transformed the environments of entire continents by systematically ring the land. Australian archaeologist Rhys Jones (1941–2001) coined the phrase

“ restick farming” to describe how Australian aboriginal communities used re to manage their environments. By regularly ring the land, they limited uncontrolled res and stimulated new plant growth, which attracted prey species such as kangaroo. Similar practices were used in other parts of the world, including North America. Over thousands of years, restick farming transformed entire landscapes. In Australia, for example, it encouraged the spread of re-resistant In Australia, 70% species such as eucalypts. This means that the of mammals over landscapes observed by the rst Europeans to encounter Australia were not “pristine” at all; in 44 kg in weight their way, they were as manicured as the gardens may have vanished of 18th-century Europe.

(about 60 species).

Humans may also have driven many large mammal species to extinction in a series of “megafaunal extinctions.” In the last 50,000 years, many large mammal species have died out, including mammoth, giant kangaroos, saber-toothed tigers, and North American horses. Most extinctions occurred in newly colonized lands such as Australia and the Americas. In Australia, 70% of mammals over 44 kg in weight may have vanished (about 60 species). The dates of these extinctions suggest that they coincided with the arrival of humans and may have been caused by overhunting, though climatic changes may also have played some role. “Megafaunal extinctions” transformed the biota of entire continents. However, there still remains disagreement about the precise contribution of humans to these extinctions. Among the earliest victims of our increasing ecological power were our closest relatives, Homo ergaster and Homo neanderthalis, both of which vanished about 20,000 to 30,000 years ago. We have seen that a lot happened in the Paleolithic era, a clear sign of our species’ remarkable capacity for adaptation and innovation. By the end of the last ice age, 10,000 years ago, humans had spread to all parts of the world, and there was no room left for further “extensi cation.” Then, in several quite separate parts of world, a new type of technology appeared: agriculture.

Essential Reading

Supplementary Reading

Questions to Consider

Christian, Maps of Time, chap. 7. Fagan, People of the Earth, chaps. 4–6. Ristvet, In the Beginning, chap. 1.

Christian, This Fleeting World. Flannery, The Future Eaters. Mithen, After the Ice.

1. Does human history during the Paleolithic era support the claim that we are, indeed, radically different from all other animals?

2. What enabled our ancestors to settle almost all of the world during the

Paleolithic era?