3-D renderings of four skeletons found buried near the altar of an early church in the Jamestown settlement in Virginia. Smithsonian X 3D hide caption

itoggle caption Smithsonian X 3D

This clay facial reconstruction of Kennewick Man, who died about 8,500 years ago in what's now southeast Washington, was based on forensic scientists' study of the morphological features of his skull. Brittney Tatchell/Smithsonian Institution hide caption

itoggle caption Brittney Tatchell/Smithsonian Institution

Humans have influenced Earth's history for thousands of years, though some scientists count changes of the last two centuries as especially notable. (Left to right) Universal History Archive/UIG via Getty Images; Hulton Archive/Getty Images; Liszt Collection/Heritage Images/Getty Images; Joint Task Force One/AP hide caption

itoggle caption (Left to right) Universal History Archive/UIG via Getty Images; Hulton Archive/Getty Images; Liszt Collection/Heritage Images/Getty Images; Joint Task Force One/AP

During a wildlife survey in Madagascar, Mayor discovered a new species of mouse lemur. "[It] weighs less than two ounces, fits in the palm of your hands," she says. Mark Thiessen/Courtesy of Mireya Mayor hide caption

itoggle caption Mark Thiessen/Courtesy of Mireya Mayor

In this June 2013 photo provided by National Geographic, diver Susan Bird, working at the bottom of Hoyo Negro, a large dome-shaped underwater cave in Mexico's Yucatan Peninsula, brushes the Naia skull found at the site. Paul Nicklen/AP hide caption

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A Filipino chicken vendor in Quezon City, east of Manila, Philippines. Researchers say Pacific island chicken are genetically similar to the variety found in the Philippines, but different from South American chicken. Rolex Dela Pena/EPA/Landov hide caption

itoggle caption Rolex Dela Pena/EPA/Landov

Area A of the Happisburgh archaeology site in Norfolk, Britain, where coastal erosion has revealed mudflats containing 800-thousand-year-old footprints. Martin Bates/British Museum/EPA/Landov hide caption

itoggle caption Martin Bates/British Museum/EPA/Landov

Human evolution is an unfolding process with chapters yet to be written; no one really knows where we're going. But we can look back to earlier chapters, with ancestors like Australpithecus afarensis, including the individual we call "Lucy" (seen above), for an understanding of how evolution works and what has happened to us over time. Tim Boyle/Getty Images hide caption

itoggle caption Tim Boyle/Getty Images