Chapter 14 Lessons From the Past, Lessons For the Future

Chapter Outline  How Successful Are We?  Humans and the Impact of Culture  The Loss of Biodiversity  The Present Crisis: Our Cultural Heritage?

Neolithic  The period during which humans began to domesticate plants and animals.  The Neolithic is also associated with increased sedentism.  Dates for the Neolithic vary from region to region, depending on when domestication occurred.

Mesolithic  The period preceding the Neolithic, during which humans increasingly exploited smaller animals (including fish), increased the variety of tools they used, and became somewhat less nomadic.

Map of Deforestation

The Loss of Biodiversity  Biodiversity is the totality of all living things, from bacteria and fungi to trees and humans.  We are currently losing biodiversity, but we don’t know the exact rate of loss or what its impact will be.  The geological record indicates that in the past 570 million years, there have been at least 15 mass extinction events, two of which altered all of the earth’s ecosystems.

Mass Extinction Events  The first occurred 250 million years ago and resulted from climatic change following the joining of all the earth’s landmasses into one supercontinent.  The second event happened 65 million years ago and ended 150 million years of evolutionary processes that produced the dinosaurs.  This is believed to be the result of climate changes following the impact of an asteroid.

Mass Extinction Events  A third major extinction event is occurring now, and may have begun in the late Pleistocene or early Holocene  Many scientists believe several large mammalian species were pushed toward extinction by humans, near the end of the Pleistocene, some 10,000 years ago.  In North America, at least 57 mammalian species became extinct, including the mammoth, mastodon, giant ground sloth, saber-toothed cat, several large rodents, and numerous grazing animals.

Overpopulation  Scientists estimate that around 10,000 years ago, only about 5 million people inhabited the earth.  By A.D. 1650, there were perhaps 500 million, and by 1800, 1 billion.  Between 10,000 years ago and A.D population size doubled 71 times.

Overpopulation  Dates and associated population estimates up to the present are as follows:  mid-1800s, 1 billion  1930s, 2 billion  mid-1960s, 3 billion  mid-1980s, 4 billion  present, 6 billion

Line Graph Depicting Exponential Growth of Human Population

The Greenhouse Effect And Global Warming  Activities involved in the production of goods and services produce waste and pollution, all of which leads to environmental degradation.  Much of the energy used for human activities is derived from burning of fossil fuels.  Burning fossil fuels releases carbon dioxide into the atmosphere, and this, in turn, traps heat.

Deforestation  Deforestation contributes to global warming, since we’re reducing the number of trees available to absorb carbon dioxide.  In the tropics, trees are burned as land is cleared, a practice that releases yet more carbon dioxide.  An estimated 20% of all carbon dioxide emissions are accounted for by the burning of the Amazon rain forest alone.

Climate Change  Since records began being kept in 1860, the 1990s were the hottest decade, followed closely by the 1980s.  The year 2002 had the distinction of being the warmest year on record, with 1998 running a close second.  The summer of 2003 was the hottest on record in Europe, and for the first time in recorded history, the temperature reached 100°F in London.

Climate Change  According to the U.N. Intergovernmental Panel on Climate Change, the average surface temperature of the earth increased by 0.8 C between 1961 and  An increase in the mean annual temperature worldwide of 0.5–1°C could result in melting of the polar caps and flooding of coastal areas.  Experts believe Greenland’s ice sheet will disappear if temperatures increase 3.0°C.  This could raise sea levels by as much as 23 feet over the next 1000 years.

Quick Quiz

1. The population of the world today is around ______ billion. a) 2 b) 4 c) 6 d) 10

Answer: c  The population of the world today is around 6 billion.

2. The adaptive strategy of humans has always been a) fight or flight. b) culture. c) aggression. d) expansion.

Answer: b  The adaptive strategy of humans has always been culture.

3. In the past 570 million years, there have been ______ mass extinctions. a) 4 b) 10 c) 15 d) 21

Answer: c  In the past 570 million years, there have been 15 mass extinctions.

4. The problem that is linked to all other life forms and is therefore the most important problem facing human beings is a) population increase. b) competition for resources. c) polluted air. d) loss of biodiversity.

Answer: a  The problem that is linked to all other life forms and is therefore the most important problem facing human beings is population increase.