Explore Geology


Life in the Cenozoic Era

the last 65 million years

From simple beginnings, endless numbers and countless varieties of life forms have evolved and populated the Earth. For 140 million years prior to the Cenozoic Era, dinosaurs held dominion over the land. Mammals existed, too, but they were small and not particularly abundant. As the dinosaurs perished, the mammals took center stage. Even as mammals increased in numbers and diversity, so too did the birds, reptiles, fish, insects, trees, grasses, and other forms of life.

The fossil record gives us a fascinating glimpse into the Cenozoic Era. Without fossils, we would have no way of knowing that ancient animals and plants were any different from today's. With fossils, we discover that an extraordinary procession of creatures lived in North America and around the world. Species changed as the epochs of the Cenozoic Era passed. Those that could tolerate the changes in the environment survived; those that could not were doomed to extinction. The fossil record reveals the story of both.

National Parks and Monuments
with significant Cenozoic fossils.

Yet, the study of fossil remains (paleontology) raises many questions. Paleontologists look beyond the fossils and ask new questions about the types of environments these plants and animals lived in and how they adapted to climatic changes. These scientists study how different groups of plants and animals interrelate, and how they have changed through time. Fossils are studied in the context in which they were found and as one element among a community of organisms.

Every fossil can serve as a key to unlock knowledge, and the National Park Service is especially concerned with the protection of these keys as the questions unfold. As the Cenozoic Era continues today, scientists estimate that up to 30 million species of animals and plants inhabit the Earth now, a mere fraction of all the forms of life that have ever existed. Scientists believe that about 100 species will become extinct every day, a rate much faster than at other times in Earth's history. The pollution of the air and water, the destruction of forests, grasslands, and other ecosystems, and other adverse changes to the Earth's environment challenge life's very ability to survive. One Finnish scientist, Björn Kurten, put it this way:

"Looking back on the long panorama of Cenozoic life, I think we ought to sense the
richness and beauty of life that is possible on this Earth of ours. . . .
And we should also realise that man, who is now planning for his own or the next generation,
must begin to plan . . . for the geological time that is ahead. . . .
It may stretch as far into the future as time behind us extends into the past."

continue to Paleocene

updated on 01/04/2005  I   http://www.nature.nps.gov/geology/parks/Age_of_Mammals.cfm   I  Email: Webmaster
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