1970s: The floppy disc appears in 1970, and the next year, Intel introduces the microprocessor, the "computer on a chip." Also, the first testtube baby is "born." These technological events inaugurate a change in humanity's relationship with nature.

Today: With the advent of genetic engineering and the increasing reliance on the Internet for work and entertainment, Americans continue to reshape the ways in which they interact with nature and other cultures.

1970s: Before the Clean Water Act of 1972 is passed, only a third of America's water is safe for fishing and swimming, wetlands losses are estimated at more than 4,600,000 acres annually, and sewage treatment plants serve only 85 million people.

Today: Two-thirds of America's waters are safe for fishing and swimming, wetlands losses are estimated at about 70,000 to 90,000 acres, and wastewater treatment facilities serve 173 million people.

1970s: In 1970, on April 22, the first "Earth Day" is celebrated...