Here's a thought: Since the pilgrims landed at Plymouth Rock in 1620, more than 500 species, subspecies and varieties of animals and plants in North America have become extinct.
In Ohio, that includes the Carolina parakeet, ivory-billed woodpecker and the passenger pigeon, the last of which died 100 years ago in captivity at the Cincinnati Zoo.
Extinction throughout history, in America and beyond, is the subject of a new exhibit at the Ohio History Center, formerly the Ohio Historical Society, 800 E. 17th Ave.
"Going, Going, Gone? Endangered and Extinct Species" will be on display through Jan. 4, 2015.
It features specimens of extinct species that lived in the state of Ohio as well as those of threatened or endangered species from across the country.
David Dyer, the center's curator of natural history, said there have been five extinction periods in Earth's history.
The Ice Age, for example, wiped out about 70 percent of large mammals. One of those was the giant beaver, an animal that inhabited Ohio, weighed about 100 pounds and was roughly the size of a modern black bear. A replica of the beaver is on display at the exhibit.
Some say the sixth extinction period is happening right now, he said.
Dyer said the display also shows some of the endangered and threatened species in Ohio, including the timber rattlesnake, the Eastern Massasauga rattlesnake, whooping crane and sandhill crane.
Dyer said dinosaurs did not wander what is now Ohio. People sometimes confuse the mastodon, which did take up residence in the Buckeye State, as being a dinosaur when in fact, it was a mammal, he said.
Theories abound as to what has killed so many species over the course of 440 million years. Scientists agree that extinction is caused by natural physical and biological conditions. It is believed that dinosaurs, which lived up through 65 million years ago, were eliminated by the effects of a giant asteroid hitting earth.
In more recent years, scientists attribute the death of species to the loss of habitat, pollution and overhunting.
The gallery includes a display on how people can help the planet and protect endangered species. It also includes inspirational stories, such as the work of Columbus native Stephen Kress, vice president for bird conservation for the National Audubon Society. Among his accomplishments, Kress reintroduced Atlantic puffins to Maine.
"All is not hopeless," Dyer said.
Hours for the exhibit are 10 a.m. to 5 p.m. Wednesday through Saturday, noon to 5 p.m. Sunday.
Admission is $10, $9 for senior citizens, $5 for children ages 6-12 and free for children younger than 5.
For more information go to ohiohistory.org.