If each mile of highway I-80 in Nebraska represented a million years of natural history, then the 450 miles from the 60th St. on-ramp in Omaha to the westernmost exit at the Wyoming border would represent the 450 million years that encompass the time that evidence of life has been found on earth. The earth itself is more than four billion years old, or ten times older than the time scale of life described here.
The 450 million years of life on earth are correlated to the distance from Omaha to the Wyoming border, and the flora and fauna of the of each era are related to the distance travelled westward along I-80. At Omaha are sponges, corals, and mollusks; dinosaurs appear at Cozad; mammals at Sydney; humans about 75 feet from the Wyoming border; and Europeans about 3 feet from the state line.
When the last prairie has been ploughed, the last prairie-chicken silenced and the last prairie rose killed by herbicides, we might perhaps pause and wonder where they all went, and where we too have gone.
Available at: http://works.bepress.com/paul_johnsgard/333/