Prehistoric and Indigenous cultures significantly transformed their environments by constructing irrigation systems and terraces, building roads and structures, clearing forests, hunting wildlife, growing crops, and managing livestock. These behaviors were common in most habitats where humans lived, and they ushered in the Anthropocene erathe epoch defined by major human impacts on the Earth.
Prehistoric hunter-gatherers used fire to clear dense vegetation, improve mobility, and facilitate hunting. The development of agriculture accelerated the impact of humans on the surrounding landscapes. Farming often required clearing cropland, preparing soils, diverting or controlling water, and cultivating particular plant species. Forests and grasslands were converted into fields and pastures, while domesticated animals altered grazing patterns. Irrigation systems changed rivers, wetlands, and soil chemistry.
Prehistoric and Indigenous cultures were responsible for contributing to the extinction of scores of animal species during the Late Quaternary extinction events. In that time, the majority of the world’s megafaunalarge animalswent extinct. Humans caused some of those extinctions by a combination of over-hunting and destruction of the animal's natural habitat. The extinctions occurred on all continents (except Antarctica) as humans moved into new regions. Because large animals typically had long gestation periods and low reproductive rates, even small hunting pressures could lead to a population collapse. Evidence for humans as a cause of some of the extinctions includes a strong temporal correlation between the arrival of humans and the subsequent rapid disappearance of megafauna, coupled with the lack of evidence of sudden climate changes at the same time. The elimination of megafauna and the modification of landscapes had cascading effects on prehistoric ecosystems. Large herbivores maintained the environment by grazing, browsing, and trampling open spaces.
By 12,000 years ago, more than 90% of Earth's tropical forests and 95% of its temperate forests were inhabited and shaped by Indigenous peoples. In the modern era, alterations to the ecosystem have increased significantly, particularly after the start of the Industrial Age. Damage to the environment by modern humansparticularly by descendants of Western colonistsis more rapid and intensive than the damage caused by prehistoric and Indigenous peoples. The perception of prehistoric and Indigenous cultures in the Western imagination is sometimes influenced by myths such as the "pristine myth"the illusion that lands inhabited by prehistoric peoples were a pristine wilderness, essentially unaffected by human impact. Another myth is the "ecological noble savage"the belief that prehistoric and Indigenous peoples were role models of conservation and never damaged their ecosystems.
Impacts on habitat
Human-caused impacts on the global environment have increased significantly since the start of the Industrial Revolution in the 1700s, but humans have been impacting their surroundings since they began populating the earth. The impacts of prehistoric peoples during the Holocene were felt everywhere on Earth except Antarctica. The impacts were driven by the emergence of complex societies, and the pastoral and agricultural industries that were required to support them. According to the archaeologist Patrick Kirch:
Over the past 10,000 years, humans have altered the Earth's environment, biodiversity, landscapes, and climate. These transformations began many thousands of years in the past by traditional, Indigenous, and prehistoric cultures. These impacts began before the advent of agriculture, and the effects vary widely across regions. By 1,000 BCE, most of the planet had been transformed by humans.
Activities Prehistoric peoples significantly transformed their environments through a wide variety of activities, including: Clearing forests (sometimes with anthropogenic fire) and harvesting wood Hunting wildlife and foraging food Growing crops Herding livestock and pastoralism Constructing irrigation systems, wells, dams, canals, and terraces Building settlements, roads, and structures Mining stones, materials, and metals Polluting
Three types of human societies played a role in habitat modification: first was hunting-gathering, followed by agriculture, and then pastoralism.
Scholars have measured the impacts of humans and found (as of 2021) that between 75% and 95% of the world's ice-free land has been transformed by people. Humans altered their habitat by polluting, emitting greenhouse gases, fragmenting, altering or destroying habitats, and introducing invasive species.
Impacts
Human activities often damaged the planet's ecosystem and natural environment. Impacts included plant and animal extinctions, greenhouse gas emissions, climate change, soil erosion, deforestation, and dominance of cultivated plants over endemic species.
Long before the First Agricultural Revolution 10,000 years ago, they were modifying their habitats with anthropogenic fires. Evidence in Africa shows that about 85,000 to 60,000 years ago, human-created fires were changing the landscape, altering vegetation, increasing soil erosion, and creating alluvial fans. Thus, the human-driven habitat impacts that came with the agricultural revolution can be viewed, not as a new mode of habitat alterations, but an evolution of fire-driven impacts.
The rise of agricultural cultures in the early Holocene accelerated the speed and magnitude of environmental impacts. Many of the agriculture-related impacts have resulted in irreversible changes to natural landscapes around the world. Impacts from agriculture include landscape erosion, conversion of habitat to cropland, animal extinctions, deforestation, and resource depletion.
When prehistoric humans began developing large-scale agriculture projects about 7,000 years ago, they cleared forests, which may have indirectly caused in increase in the amount of greenhouse gases (including CO and methane) in the atmosphere. The use of farming technologies such as iron and plows accelerated the impacts. This marked the start humankind's contributions to the modern climate change crisis.
In addition to agriculture, pastoralism also played a major role in modifications to the landscape. Enabled by the domestication of livestock, pastoralism spread across much of the world between the years 10,000 and 3,000 years ago.
Some traditional land use practices produced cascading environmental consequences, sometimes leading to extinctions of animal species. Historical land use practices have both improved and degraded the environment: sometimes damaging soil, other times enriching it; sometimes destroying habitat, other time creating new habitats; sometimes causing animal extinctions, other times propagating domesticated species.
Deforestation
One of the most consequential impacts of human activity was deforestation. Anthropogenic fires were widely used to clear vegetation, perhaps as early as a half million years ago by Homo erectus. Techniques used for clearing forests included axes, animal grazing, and slash and burn.
Ten thousand years ago (10 kya) the world's forest cover was about 6 billion hectares. By 5,000 years ago (roughly in the middle of the First Agricultural Revolution) the coverage had been reduced by 170 million hectares. In 2023 it was 2 billion hectares below the 10 kya coverage.
By 12,000 years ago, more than 90% of Earth's tropical forests and 95% of its temperate forests were inhabited and shaped by indigenous peoples.
Extinction of animals
During the Pleistocene epoch, Earth supported an astonishing variety of large animals including saber-toothed tigers, terror birds, wooly mammoths, giant tortoises, giant ground sloths, and huge armadillos. Those species, and many other large animals, became extinct, with human activity acting as a driver for many. The loss of large animals such as these may give some modern people a sense of loss.
The loss of hundreds of species of megafauna fundamentally altered the Earths ecosystem.
Over the past 129,000 years many megafauna species around the world became extinct. Although extinctions are common in the geological record going back many millions of years, the speed and magnitude of the extinctions since 129,000 years ago is unusual. The majority of large land animal species living in the world 100,000 years ago have become extinct since then. Among these extinctions are over 350 mammal species, which reduced the global count of mammal species (of all sizes) to approximately 5,700 in 2020. In the Americas, over 66 genera (over two thirds) of large mammals became extinct. In North America alone, about 38 genera of large animals became extinct, including 19 genera of mammals.
The extinctionsthough occurring in a brief time span when considered geologicallyoccurred at different times around the globe. These extinctions happened during the latter part of the Quaternary geological periodextending from about 129,000 years ago to the present. The extinctions are sometimes divided into two groups: extinctions during the Late Pleistocene (between 129,000 and 11,700 years ago), and extinctions during in the Holocene (from 11,700 years ago to the present).
Causes of extinctions
Academics have explored the causes of the Late Quaternary extinctions since the early 19th century. Since the late 20th century, the debate over the cause of the extinctions was vigorous, and often focused on the extent to which humans were responsible for the extinctions. Causes proposed for the extinctions include: Human causesOver-hunting; second-order predation (over-hunting an herbivore species upon which the extinct species fed); habitat alterations or reductions; introduction of invasive species; anthropogenic fires (fires set by humans, deliberately or accidentally) resulting in loss of habitat or lack of forage; pollution Climatic causesIncluding gradual climate changes, as well as rapid changes such as Younger Dryas or Clovis age drought Infectious disease Natural extinction of herbivores leading to extinction of carnivores Impact of an extraterrestrial object Synergistic combination of multiple causesFor example, human activities (fire, hunting, agriculture, deforestation) contributing to climate change
The two primary causes considered by researchers are climate change and human activity. Most of the recent megafauna extinctions occurred after the arrival of humans, but proving cause-and-effect is difficult due to the fact the events happened long in the past. The nature of the extinctions varied between species and locations.
Extinctions caused by human activity
A large number of Late Quaternary megafauna extinctions were a result of human activity, including hunting and habitat destruction. Evidence for humans being the primary driver include the timing of extinctions following human arrival, the lack of climate change at the time of extinctions, archaeological evidence of hunting and habitat destruction, geographic correlation of human presence and extinction events, and analysis of large fauna that did not go extinct. Humans were not responsible for all megafauna extinctions. A 2021 study of extinctions on islands found that while extinctions during the Holocene were often caused by humans, earlier Pleistocene extinctions often were not. Some scholars, as of 2020, argue that the extinctions in North American were primarily caused by climate changes.