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The Age of Humans: Evolutionary Perspectives on the Anthropocene

A composite image of Earth at night. The lights include city lights, gas flares, and wildfires. (NASA Earth Observatory image)
A composite image of Earth at night. The lights include city lights, gas flares, and wildfires. (NASA Earth Observatory image)

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What is the Anthropocene?

Human activity has fundamentally changed our planet. We live on every continent and have directly affected at least 83% of the planet’s viable land surface. Our influence has impacted everything from the makeup of ecosystems to the geochemistry of Earth, from the atmosphere to the ocean. Many scientists define this time in the planet’s history by the scale of human influence, and label it as a new geological epoch called the Anthropocene.

As of 2005, humans had built so many dams that nearly six times as much water was held in storage as flowed freely in rivers.
As of 2005, humans had built so many dams that nearly six times as much water was held in storage as flowed freely in rivers.

Geological epochs are one of the definable units that geologists and paleontologists use to break down the broad concept of deep time. These units of time are defined by stratigraphic layers that are chemically or biologically distinct. Epochs are defined on a global level, and their beginning and end are dated to specific points in time. Hominins first appear by around 6 million years ago, in the Miocene epoch, which ended about 5.3 million years ago. Our evolutionary path takes us through the Pliocene, the Pleistocene, and finally into the Holocene, starting about 12,000 years ago. The Anthropocene would follow the Holocene.

A visual representation of the breakdown of geological time.
A visual representation of the breakdown of geological time. The Anthropocene would come after the Holocene.

 

A composite image of Earth at night. The lights include city lights, gas flares, and wildfires. (NASA Earth Observatory image)
A composite image of Earth at night. The lights include city lights, gas flares, and wildfires. (NASA Earth Observatory image)

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When did it begin?

The beginning of the Anthropocene is a subject of heated debate among geologists, anthropologists, and others in the scientific community. In order for the Anthropocene to become officially recognized as a geological epoch by the International Commission on Stratigraphy, a start date must be recognized that is global and can be defined stratigraphically by biological, chemical, or other types of markers. Some geologists argue that this is impossible to identify because we are still within the range of variation of any signal that might distinguish recent strata from earlier ones, or because human activity is diverse enough that no single moment universally distinguishes a period of time separating the Anthropocene from the Holocene. But even among those who believe that this beginning date can be pinpointed, there is still considerable disagreement.

The boundaries of each unit on the geologic time scale are marked with a "golden spike", to signify the type section of a particular unit of geologic time.
Golden spikes are used by geologists to define major geological time boundaries and large changes in Earth’s biota, such as the Ediacaran Biota dated around 635 million to 542 million years old.

Some argue that the Anthropocene began with the advent of agriculture, because certain agriculture-related activities such as rice paddy irrigation and deforestation may have led to sharp rises in concentrations of CO2 and methane as early as 8,000 years ago[i] . Many believe that it was not until the Industrial Revolution that our exploitation of fossil fuels and monumental increases of energy use and population started to push us far enough to “show a discernible human influence beyond natural [Holocene] variability."[ii] A third proposed start date is the Great Acceleration, or the beginning of the nuclear age in the mid-1940s. In this period, not only did our testing and use of atomic weaponry leave a distinctive radioactive signature in the sediments of Earth, but almost all human activities from water use to fertilizer consumption to globalization saw a dramatic intensification[iii].

The sharp upward spike in all of the trends displayed on this graph show how human activity has increased since the Great Acceleration.
The sharp upward spike in all of the trends displayed on this graph show how human activity has increased since the Great Acceleration.

  • [i] Ruddiman, William F. "How Did Humans First Alter Global Climate?" Scientific American 292 (2005): 46-53.
  • [ii] Steffen, W., J. Grinevald, P. Crutzen, and J. Mcneill. "The Anthropocene: Conceptual and Historical Perspectives." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 369, no. 1938 (2011): 842-67.
  • [iii] Ibid.
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Why does the Anthropocene matter?

No matter when it began, the concept of the Anthropocene is significant. It highlights the scale of our impact on Earth. By defining a new geological epoch, we are declaring that the impact of our activities is global and irreversible. It allows us to unite many different discussions regarding the state of the planet, from climate change to loss of biodiversity to environmental degradation, by identifying the one thing they have in common: they have all been affected by human influence.

Human pollution shows the impact of the Anthropocene. It destroys natural landscapes and poses a critical danger to many animals.
Human pollution shows the impact of the Anthropocene on many issues. It destroys natural landscapes and poses a critical danger to many animals who may consume or become entangled.

The Anthropocene also allows us to reexamine the relationship between humans and the rest of the natural world. There has been a long-standing narrative of humanity and nature being separate; some believe that we should be the caretakers or stewards of the natural world, while others urge us to leave the environment alone and let nature run its course. But human activity is intrinsically linked to nature, and is part of it. From the land we live on to the resources we use to the trash we throw away, everything we do is tied into and impacts our surroundings. The concept of the Anthropocene underlines this fact by defining the environment based on the interactive effects of our influence. The only question now becomes how we can shape our activities so our impact on the environment is intentional and leads to meaningful outcomes.

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State of the Planet

Smog in the Forbidden City in Beijing, China.
Smog in the Forbidden City in Beijing, China.

We all know that humans have unmistakably influenced the planet, but what does that influence look like? The most familiar parts of this story are where we have most physically altered the planet. Greenhouse gasses such as CO2 (carbon dioxide), CH4 (methane), and N2O (nitrous oxide) caused by fossil fuel combustion and industrial processes are increasingly concentrated in our atmosphere, causing heat to become trapped on Earth and resulting in rising global temperatures[iv]. The projected estimate for mean surface temperature increase by 2100 is 6.7° F to 8.6° F (3.7° C to 4.8° C)[v], which would make Earth hotter than it’s been in 14 million years[vi]. On our current path, ice cap melt will cause sea levels to rise to levels where many major cities will be at very high risk of flooding, and natural disasters will cause damage to our communities at catastrophic levels on a much more regular basis[vii]. Forests are shrinking at a startling pace – every year, we lose a swath of forest the size of Massachusetts[viii]. If temperatures rise by only the most conservative estimates, at least 20-40% of Earth’s animal diversity will be at increased risk of extinction, and pollution and poaching will lead to the extinction of dozens more species[ix]. All of these problems are exacerbated by an ever-growing human population, which has more than doubled in the last fifty years. But while climate change is one of the most visible parts of the Anthropocene, it does not paint the whole picture of our influence. Everything from damming rivers to paving roads to illuminating public spaces has changed the physical makeup of the planet in some aspect, creating a world that has truly been shaped by humans.

Animals like the polar bear are vulnerable to extinction due to health risks from pollution and rising temperatures caused by human influence.

Vaccines that train our bodies to fight viral infections have revolutionized how we perceive disease, and have saved millions of lives.
Human creativity has produced some incredible achievements. We have created the technology to produce high-yielding food crops with the capacity to support more human life than ever before. We can plant crops far from water sources, control the temperature inside our living spaces, enjoy leisure time and luxuries, and walk on the moon. We have invented cures for diseases that were once catastrophic. We can travel anywhere on Earth at incredible speeds in cars, ships, and airplanes. Three-quarters of the world’s population has cell phone access[x], and as of 2013, nearly 40% of individuals had access to the Internet[xi] , allowing people to communicate and access knowledge that was once much more restricted. These innovations in transportation and communication have given us the means to connect with our fellow human beings, learn about new cultures, and maintain relationships all around the globe.

Access to cell phones and the internet have allowed humans to connect to and communicate with people around the globe nearly instantaneously.
Access to cell phones and the internet have allowed humans to connect to and communicate with people around the globe nearly instantaneously.

Perhaps most importantly, we have self-awareness of the impact of our activities. Scientific methods can help us comprehend how emissions from our vehicles and factories are causing Earth to warm, and how that warming will affect everything from sea levels to biodiversity. We can study how the use of certain fertilizers on land will destroy marine ecosystems thousands of miles away. We are aware of the finiteness of Earth's natural resources and can use this knowledge to analyze the short- and long-term effects of their gradual depletion. And we have the capacity to create innovative solutions, like solar panels that convert the sun’s energy into usable power, recycling systems that allow us to reuse plastics instead of polluting Earth with them, and vehicles designed to run on renewable, non-polluting energy sources instead of fossil fuels. Having this self-awareness along with our creative problem-solving will be critical to helping repair some of the negative effects of the Anthropocene, and will help us to be conscious of those effects into the future.

Many countries are starting to convert to renewable energy sources, such as wind power, shown by these turbines.

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Human Evolution and the Anthropocene

Changing climate is not a unique feature of the Anthropocene. Earth’s environments have been in a constant state of creation, destruction, and change for the planet’s entire history. The last six million years (when hominins began to appear in the fossil record) were particularly volatile and saw many different shifts in environments. The key to human survival in these settings was an extraordinary ability of our ancestors to alter their behavior and the world around them. Our success in these times was largely due to the evolution over time of a number of traits that allowed us to be more adaptable to a large variety of environmental conditions.

Slice of Time
The layers of sediment visible on this hillside in the Rift Valley of southern Kenya illustrate change in the environmental conditions faced by human ancestors around 1 million years ago.

The first bipedal hominins were able to live both on the ground and in trees, which gave them an advantage as the habitat oscillated between forests and grasslands. The ability of early humans to make and use tools, including the control of fire, allowed them to more easily access food by scraping meat off of bones more efficiently, crushing bones for the marrow inside, and obtaining new plant foods such as nutritious tubers and roots from underground. Tool use also enabled early hominins to diversify their diet, so they had plenty of options when certain plants and animals went extinct. And with a larger and more complex brain, early humans gained the capacity for everything from language to creative problem-solving. When humans began to expand out of Africa and into the rest of the world, they moved everywhere from mountains thousands of feet above sea level to blazing hot and extremely arid deserts, displaying an astonishing ability to adapt to the wide diversity of Earth’s environments.

These objects and fossils display many of the characteristics of human adaptability over time.
These objects found in Africa illustrate the many thousands of clues discovered about human origins, including use of tools and symbols, increasing brain size, and footprints indicating walking upright.

Reconstruction of close evolutionary cousins, Neanderthals, based on the skull from Shanidar 1, Iraq.  Artwork: John Gurche. Image credit: Human Origins Program, Smithsonian.
Reconstruction of close evolutionary cousins, Neanderthals (Homo neanderthalensis), based on the skull from Shanidar 1, Iraq. (Artwork by John Gurche)
Other species in our evolutionary tree had features that were more specialized to one particular environment, and they were very successful for long periods of time in those environments. Yet these localized features restricted their ability to live in new conditions, limiting how effectively they could inhabit new geographic zones or could adjust to unusual climatic shifts. If they were unable to adapt to new conditions or change their location significantly, they died out. A good example of that are the Neanderthals, or Homo neanderthalensis. Members of this species had bodies that were well suited for cold climates; their short, stocky bodies, large noses, and their ability to make clothing were all specialized features for successful living in the cold. In contrast, Homo sapiens had an extremely enhanced ability to adapt their behavior to new surroundings, despite having physical features more suited for an African climate. It became particularly difficult for Neanderthals to compete with the innovative Homo sapiens, and with a geographic range limited by their specialization to cold, they eventually went extinct. While Neanderthals and all other early human species exhibited some of the human characteristics of adaptability, Homo sapiens distinguish themselves with an extreme reliance on altering their landscapes and themselves for survival.

A chart describing the close relationship between early human lineages, technological innovation, and the longest periods of strong climate variability in East Africa.
A chart describing the relationship between early human lineages, technological innovation, and periods of strong climate variability in East Africa.

The volatility of past climates does not diminish the effects of human activity in the Anthropocene. The types of changes that we have seen in the last two hundred years are far outside the range of variability we see in the past. Examining the Anthropocene through the lens of our evolutionary history shows us that the themes of resilience and adaptability are critical to the history of our species in the past and in the Anthropocene. These distinctive traits of our lineage have created a human species that is defined by its ability to alter its behavior and environment as a mode of survival. These themes are critical to understanding how the Anthropocene has come to be, and how we will survive into the future.

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No Turning Back: The Future of the Anthropocene

This terraced landscape is an example of human activity influencing the landscape.
We can never return the environment to how it was in the past. The conditions of the past have been so varied that there is no stable baseline on which to base what "the past" looked like. So if we can’t reverse the clock, how do we move forward in this altered world we’ve created?

The present climate change dialogue has mostly been centered on the apocalyptic consequences of continuing down our current path, and for good reason: almost a quarter of Americans don’t believe that human-induced climate change is happening[xii]. Stories of mass extinctions and the destruction of our major cities are useful tools to put the urgency of our situation in perspective. None of this is inaccurate, and it is critical that the public, and especially those in positions of power, understand the scope of influence our species has had on the planet.

But oftentimes this dialogue leaves out a critical perspective: what we can do to change our behavior and environment to create a positive future. The story of human evolution features a unique ability to adapt in the face of changing climates, and this will be no different for human-shaped climates of today and the future. With our own growing awareness of how our actions impact the natural world, the question is how best we can shape our actions so that the consequences of our activities are purposeful and positive.

Altering our surroundings is fundamental to human survival. In this light, how may we come to alter the world that we've created in a conscious and productive way? Community and global collaboration, along with innovation, will be the keys to creating a new path for the future of our species and our environment. By looking at the Anthropocene from a human origins viewpoint, the narrative of our collective humanity and the qualities that unite us as a species with a common origin can give us a sense of communal purpose in developing solutions for the problems of the Anthropocene.

People come together from across the globe for the 2014 Peoples' Climate March in New York on September 21, 2014.
People come together from across the globe for the 2014 Peoples' Climate March in New York on September 21, 2014.

These are some of the many questions that we must answer as we begin to craft the future of the Anthropocene:

  • Whose responsibility is it to make important decisions?
  • How do we shape a global social project?
  • How do we accommodate cultural diversity while making changes at a global level?
  • How do we make long term changes (toward a sustainable future) appealing, feasible, and accessible for individuals, countries, etc., on a short-term scale?
  • What do we want the future to look like?
  • What do we want life on this planet to be like?
  • What can we do as individuals, countries, and organizations to create a future with purposeful intentions?
  • How can we act as individuals to get the ball rolling?
  • Which issues are the most critical to address first?
  • How do we begin?

Contemplating these questions will help us begin to determine the future of the Anthropocene. The themes of self-determination, community, and action will all be parts of the human-driven innovation for the future of the planet. As we look to the future, we will see not only the planet change, but we may even see changes in ourselves as a species. We invite you to contemplate: What will it mean to be human in the future of the Anthropocene?

  • [xii] Leiserowitz, A., Maibach, E., Roser-Renouf, C., Feinberg, G., Rosenthal, S., & Marlon, J. Climate change in the American mind: Americans’ global warming beliefs and attitudes in November, 2013. Yale University and George Mason University. New Haven, CT: Yale Project on Climate Change Communication. (2014).
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Further Reading

References

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Page last updated: October 13, 2016