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Human Arrival and Expansion

Human Arrival and Expansion

Author: Jensen Morgan

This lesson explains the context of humans on earth and provides an overview of human population growth.

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Human Arrival & Expansion

Source: Earth PD http://bit.ly/1ESoBKp Edinburgh PD http://bit.ly/17VsLGb Ice Core CC http://bit.ly/1wYdlXV California PM CC http://bit.ly/1wJE9Ay Pie Chart CC http://bit.ly/1DYNG6D Chart Tool CC http://bit.ly/1BUnHiZ Deforestation, PD http://bit.ly/1Ci1x9N Ocean Trash CC http://bit.ly/1DyPkdy

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Hi, I'm Jensen Morgan. We're going to talk about some great concepts in environmental science. Today's topic is Human Arrival and Expansion. So let's get started.

We're going to talk about human history, human population growth, population explosion, and what has sustained human population growth. Like we discussed in an earlier video, we're going to compress history into a year. But this time, it's going to be just earth's history, not universal history.

So starting January 1st, 4.5 billion years ago, the earth was formed. 660 million, or by this scale, 11 months later by mid-November, every major group of multicellular organism had evolved. 5 to 8 million years ago, or somewhere between 9:00 AM and 2:00 PM on December 31st, human evolution began. Approximately 200,000 years ago, or at about 11:37 PM, December 31st, Homo sapiens evolved.

Over time, human behavior and skills have changed and evolved. During the Old Stone Age between 200,000 and 10,000 years ago, humans, or Homo sapiens, were hunter gatherers. They often lived in seasonally mobile small tribes.

However, with the advent of agriculture approximately 10,000 years ago, the Neolithic era began. Homo sapiens became more sedentary, primarily shifting to farming and settled communities. The invention of agriculture, along with a host of technologies and practices that resulted eventually, gave rise to human population growth and expansion.

This graph shows human population growth since 1000 CE or AD. From about 200,000 BCE to about 8,000 BCE, human population remained relatively low. The Black Death and widespread famine reached its zenith around 1350. Yet human population was still beginning to expand.

As the Black Death and widespread famine receded, human population experienced continuous growth since 1350 and really began to climb, reaching 1 billion only 450 years later. The population doubled to 2 billion in only 127 years, and then doubled again by 1999 to 6 billion.

If you look at the addition of a billion people, it took 127 years the first time, 32 years the second time, 15 the 3rd, 13 the fourth time, 12 the fifth, and 13 the last time in 2012, bringing the world population to 7 billion. It is still climbing.

Population growth really exploded following the beginning of the Industrial Revolution because population growth expanded cities and infrastructure, the revolution increased access to safe drinking water, cities allowed large amounts of energy to be centralized for human use, new forms of transportation allowed people to become more mobile.

The Industrial Revolution combined with the Green Revolution in the mid-1900s increased food productivity and reduced famine drastically. The Green Revolution was a combination of improved agricultural crop breeding, mechanization of farming, and chemical production of fertilizer. It increased world-wide production of food crops, especially in developing nations.

The Industrial Revolution reduced disease and increased longevity through improved nutrition, sanitation, and medicine. Human population growth has continued over time because of technological advancements in tool-making, such as the modern tractor, which increases productivity and decreases human labor requirements simultaneously, allowing for increased food productivity which can then support a larger human population.

Agricultural advancements, such as chemical fertilizers, have increased crop productivity by providing needed nutrients quickly with less human labor. This has increased food productivity and allowed for a larger human population.

In general, advances in agriculture and animal domestication have made it so that fewer people are needed to work to feed many people, which has allowed for specialization of other people's time. This specialization allowed for more technological advancements to sustain human health, which has allowed for even more population growth.

And technological advancements in industrialization such as highly-efficient manufacturing facilities, have generated goods and products that can preserve and protect human health to be cheaper and more widespread. This also has allowed for a larger human population.

In general, technological improvements have sustained human population growth because they have encouraged three things. Increased fertility-- the average number of children born to a single woman has risen because of food availability and medical care. Decreased infant mortality-- the rate of infant deaths per year has decreased due to better medical care and sanitation. And increased longevity-- human lifespans have increased due to better medical care, food production, and sanitation.

Now let's have a recap. We talked about human history, human population growth, population explosion, and what has sustained human population growth in general. Well, that's all for today. I look forward to next time. Bye.