The second section of the course dives into historical trajectories against the backdrop of the current world situation. How has human development contributed to the emergence of ecological crises? We begin with human prehistory, after which we move toward the critical issues of today. 

There are tasks associated with the materials that you will see at the end of the section.

The noble savage myth

We often tend to believe that humans have only caused ecological catastrophes after industrialization and before that, especially in prehistoric times, people lived in harmony with nature. Such an idea is old and part of the “noble Savage myth” that is commonly attributed to perhaps the greatest philosopher of the Enlightenment, Jean Jacques Rousseau.

However, according to current research, this is far from the case. While environmental damage has undoubtedly intensified wildly since man-made industrialization (over the past 300 years), the history of man-made ecological disasters is tens of thousands of years longer. One could say that at the latest since humans harnessed fire, which happened perhaps 250,000 years ago or much earlier, humans have irreversibly changed their habitat. Particularly since the rise of agriculturally based societies and associated population expansion during the early Holocene, humans have had cumulative and often irreversible impacts on nature worldwide.

However, we must remember that it is difficult to get accurate information, especially about things that happened thousands of years ago – such as the arrival of people on a new continent or the extinction of some animal species. Science does not offer complete certainty, but only constantly refined, cumulative information.

Early extinctions

The earliest human impacts on species diversity probably date back two million years. Even before humans developed into modern humans (homo sapiens), humans may have had an impact on the extinction of other large carnivores in particular. After humans evolved into carnivores about 2 million years ago, the species richness of other carnivores in Africa declined so markedly that it is unlikely that the changing climate could explain it. 

In the Late Pleistocene period, starting 126,000 years ago, the number of extinctions especially for big animals increased, strongly suggesting human influence. Large animals were undoubtedly the preferable game for hunter-gatherer communities of the prehistoric period. There are currently about 5,700 species of mammals on Earth, in addition to which at least 351 mammal species have become extinct since the beginning of the Late Pleistocene period.

After spreading from Africa to inhabit other continents as well, humans drove large animals to extinction or at least contributed significantly to the extinction of these species. In Australia this happened maybe 40,000 years ago and in Europe and Asia 40,000 – 10,000 years ago. Many large animals disappeared in North America 15,000 – 11,500 years ago and in South America 14,000-8,000 years ago.

The figure shows the spread of humans from Africa to the rest of the globe and the subsequent extinctions of large mammal species. The Quaternary Megafauna extinction killed more than 178 of the world’s largest mammals from 52,000 to 9,000 BC. For example, human arrival in Europe 35,000-45,000 years ago, with 36 percent of large mammal species extinct 23,000-45,000 years ago and later 10,000-14,000 years ago. From 8,000 to 12,000 years ago, 72% of mammal species disappeared from South America, including all ground sloth species, from 11,000 to 12,000 years ago.

Most often, the first major human-made ecological disaster is considered to be the destruction of the Australian megafauna, such as giant kangaroos, lizards, and birds, some 40,000 years ago. People had arrived in Australia possibly just a few thousand years earlier. Estimates of when humans arrived in Australia, however, vary considerably, and it is possible that humans arrived in Australia as early as 65,000 years ago. In any case, possibly as many as 85% of Australia’s mammal, bird, and reptile species weighing more than 45 pounds (about 20 kg)  became extinct from a historical perspective quite soon after humans arrived. 

According to one popular theory, humans arrived on the North American continent about 13,000 years ago and spread rapidly. The arrival was made possible by a drop in water levels, which caused a land bridge between northeastern Siberia and northwestern America. About 10,000 BC people already populated the southernmost regions of South America. However, according to current research, it is likely that people had arrived on the American continent at least a couple of thousand years before – and possibly even much earlier. Before the arrival of humans, American fauna flourished much richer than today. Twenty thousand years ago, there were more impressive numbers of large mammals in North America than in Africa today. The widespread expansion of humans through North America was likely the key factor in the extinction of large terrestial mammals. 10,000 years ago, 34 genera of mammals had disappeared, including 10 species that weighed more than a ton. In turn, South America lost 51 genera of large mammals (> 44 kg).

Hunting is perhaps the most significant of the activities that have affected other animal populations. It first led to the collapse of populations of large animals, after which the pressure of predation has shifted to smaller animals. If predation pressures remain high enough for a long time, populations will eventually disappear or entire species will become extinct. Another significant factor that altered habitat was either intentionally or unintentionally ignited wildfires. The decline in large herbivores due to hunting also exposed the emergence of wildfires as the increasing grasses allowed fire to spread more easily. 

Already in prehistoric times, when inhabiting new areas, humans also influenced animal diversity by relocating new animal species to new habitats. Sometimes animals were also moved with people by accident. In the islands, in particular, the emergence of new animals (such as lice, rats, mice, snails, and birds) has led to catastrophic consequences as new animal species have taken over the habitat of the original fauna.

Are humans to blame for prehistoric extinctions? 

Scientists have long argued over the cause of prehistoric extinctions. Climate change and human activities have become established as the main candidates. It has been suggested that, in particular, human overhunting and the wildfires they caused led to the extinction of other species. For example, people who came to Australia knew how to use fire, because people have had the skill to do so for at least 250,000 years, possibly up to 400,000 years.

The argument about the impact of humans on the extinctions of the historic megafauna is largely based on the fact that massive extinctions appear to have occurred on various continents and islands, based on archaeological and paleontological data, shortly after human arrival. This has been the case even when climatic conditions have been stable. In addition, the megafauna has had the ability to withstand climate change: many of the extinct species had lived for millions of years and gone through many changing climates. So they had survived regardless of the circumstances, but disappeared after the arrival of humans within a few hundred or thousand of years. 

It is also logical to think that the huge animals would not have been afraid of a relatively small mammal running on two legs the first time they encountered a human, which would have made them easy targets for prehistoric hunters. This also explains why there are still far more large animals in Africa than on other continents. Humans evolved in Africa along with other species. Over time, as a result of common evolution, humans became more skilled predators to which animals became accustomed over several generations, becoming more difficult to hunt. 

Theories about the effects of man on early extinctions have been criticized, among other things, for the possible arrival of humans in Australia as early as 65,000 years ago and the mass extinction of megafauna only occurring until about 20,000 years after this. On many other islands, on the other hand, extinctions have occurred more rapidly since human arrival. Also, some scholars believe that there is little reliable archaeological evidence to support the argument of human impact. It is also difficult to show exactly when a particular species has become extinct. Indeed, climate change has often been cited as an alternative cause of species extinction rather than human activity, although there does not appear to be very good evidence for the impact of climate change.

Nevertheless, it can be considered unlikely that the extinctions following the spread of humans in different geographical areas would be a mere coincidence.

Extra material online

This video goes through the issues surrounding the extinction of the megafauna: Video on Youtube

This video takes a closer look at the causes of the extinction of the Australian megafauna and also makes critical remarks regarding the evidence: Video on Youtube

Food for thought: how might the experiences of disappearing prey species in early human communities have influenced the cultures of these communities? You can share your reflections and discuss with other course participants on the page linked below.

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