Howdy! Today we're going to talk about a new epic called the Anthropocene. So what is the Anthropocene? According to Will Steffen, it's a new epic when human activities have become so profound and pervasive that they rival or exceed the great forces of nature in influencing the functioning of the earth systems. Anthro meaning human and scene meaning epic.
So the Anthropocene is a proposed new epoch in geologic time, which reflects the significant human impact on the natural environment. We've entered a new age of man. Humans have become to be such profound drivers of change in the dynamic processes of the natural environment. And throughout this course, we will discuss how humans have changed the major earth systems, including the biosphere, hydrosphere, atmosphere, lithosphere, and cryosphere. But before we can do that, we have to decide when did the Anthropocene begin?
Currently it's still under debate and scientists are trying to identify when specifically in geologic time humans began to have a significant enough impact on the Earth in order to warrant a whole new epoch. So how do we measure geologic time? In this figure to the right you'll see we have eons as the largest measurement of time.
eras, periods, and epochs. And then to the left you will see how long humans have been around. So we're currently in the Cenozoic era in the Quaternary Period and the Quaternary Period began about 2.6 million years ago. You can tell within the boundaries of geologic time humans are relatively new and we didn't show up until the Quaternary Period.
and within the Quaternary Period we have the Pleistocene Epoch, the Holocene Epoch, and under debate, the start date of the Anthropocene Epoch. It's important to understand how a new era is determined. The Global Boundary Status Type Section, GSSP for short, is an internationally recognized system that helps to identify and define geologic time.
It began in 1977 as a way to create and foster consistency classification of different stages of geologic time. It's determined by a group called the International Commission on Stratigraphy and within that group there's a working group called the Anthropocene Working Group or AWG for short. All of these are a section of the International Union of Geological Sciences and in order to define a GSPP scientists must utilize primary markers, secondary markers, and use well-preserved geologic sections and key events in order to classify the different changes in geologic time.
Just as a brief recap, we will very quickly go through human history and the evolution of environmental impacts and then throughout the semester we'll get more in-depth into each one of these. To start with, we have human colonization. So some six or so million years ago, hominids started to appear in the fossil records.
Earliest records can be found in Chad in Africa and early evidence of tool making was found in Kenya dating back to 3.3 million years ago. The first recognizable human was Homo habilis which evolved around 2.5 to 2.8 million years ago. That is approximately when the Pleistocene ice ages were also developing.
So you'll see in this figure that the human colonization is happening during the ice age of Earth. Some dates are given and provided here in thousands of years before present. Since that time, humans have spread over nearly the entire land surface of the Earth. While there is considerable uncertainty for certain parts of the world like the Americas, this figure shows the most commonly accepted dates of colonization for each continent.
Animal domestication. Humans have evolved from primarily hunters and gatherers into cultivators and keepers. Domestication of animals allowed humans to stay in place for longer rather than following animal migration routes.
This figure shows some of the major places of origin along with approximate dates for the most common domesticated animals. Cultivation of crops was a major changing point in human history. Between animal domestication and agricultural cultivation, humans were able to establish permanent homes.
And by taking up agricultural practices in animal domestication, humans were able to significantly reduce the space needed for sustaining each individual by about a factor of 500 at least, which is pretty impressive. This allowed for population densities to increase, leading to the establishment of towns and later cities. Through controlled breeding of plants and animals, humans were able to foster much more reliable sources of food, thereby creating the opportunity for more leisure time and the development of cultural advancements. Just as a brief recap of human history, we've gone through several stages of cultural and economic development. Some of the major milestones are shown in this figure.
These include the Paleolithic, time of hunters and gatherers, the Neolithic Revolution followed by the Bronze Age and the Iron Age, and in the Middle Ages human population expansion really begins to pick up steam. So how can we measure the impact of humans on the different aspects of the natural environment? Scientists have been debating the start of the Anthropocene, but what are the arguments based on?
This figure shows a logarithmic scale of the world population growth and you can tell that with each new technological innovation humans are able to expand faster and faster. This gives us the opportunity to study not only how these major stages of social and economic development happened, but also what was left behind as a result of these different technological advancements. We've already mentioned the agricultural revolution when humans started domesticating plants and animals. Early globalization occurred between 1492 when Columbus sailed the ocean blue, In the 1800s, this delineation is classified by the Old World meeting the New World, where humans began to circumnavigate the world, and early globalization began. The Industrial Revolution, which is often called the Great Acceleration, started in the late 18th century with the invention of the steam engine, and then the internal combustion engine later in the 19th century.
These technological innovations provided a major increase in access to energy and lessened the reliance on animals, wind, and water. The 20th century saw a time of incredible change where the global population soared from 1.5 to 6 billion. So, how can we measure all of these different stages of human social and economic changes? As I mentioned in the beginning, in order to classify different epochs, scientists look at primary and secondary markers within the natural environment.
This chart shows some of the major stratigraphic markers, both the primary and secondary, for measuring the human impact on the natural environment. So as you can see, we have the event on the left, the approximate date, and the geographical extent on the right. And if I add in this, we can see what those primary stratigraphic markers and secondary stratigraphic markers look like.
So, for instance, the start of the Industrial Revolution can be measured with fly ash from coal burning, while nuclear weapon detonations starting in 1945 can be measured with radionuclides or carbon-14 within tree rings. Here are a few graphs that demonstrate the change in proxy data for measuring different types of environmental change. We can look at, scientists can look at ice cores, fossil crop pollen, temperature, atmospheric carbon dioxide, methane, radioactive isotopes, and persistent industrial chemicals. This figure is really interesting because it represents the percentage of change to both the biosphere, hydrosphere, and atmosphere from assumed zero human impact of 10,000 years before present.
And you can see just how quickly some of those changes began to happen after the Great Acceleration. In May of 2019, The AWG, which again is the Anthropocene Working Group, finally voted that the Anthropocene be a formal epic and voted that it should start in 1950. I have provided a variety of readings on eCampus that will allow students to get a closer look into the debates that preceded this vote. The next step is to obtain ratification by the Executive Committee of the International Union of Geological Sciences, which has not yet happened.
So, in the meantime, do you think they're right? Do you think that the Anthropocene should begin in 1950? Why or why not? How could human bias play a role in determining the start of the Anthropocene era? What were the major decisions that the Anthropocene Working Group had to debate in order to come to a consensus?
For assignment one, please go to eCampus and read through some of the major literature provided. Also, please feel free to find your own. If you look under week one, you'll find access to all of the readings.
and videos. And next Wednesday, the first assignment will be due. So please write a one to two page paper, single spaced, 12 point font, Arial, standard margins.
You can use either APA or MLA citation style, but please be consistent throughout the rest of the semester. Please use high quality citations, so that means peer reviewed journal articles only. Citations can leak over onto a third page. But your assignment must include scientific charts, graphs, and tables in order to support your arguments.
In the meantime, check out the podcast of the week. It's a great podcast called Generation Anthropocene. And in the episode is Earth in Human Hands.
It's available on eCampus. So check it out.