The Smithsonian Institution’s National Museum of Natural History decided to do something special for its 100th birthday — explain how humans came to be.

Officials unveiled the museum’s newest initiative, “Human Origins: What Does It Mean to Be Human?” in the newly opened David H. Koch Hall of Human Origins on Wednesday, the centennial of the museum’s opening on the National Mall.

Featuring dozens of exact replicas of early human skulls, original artifacts such as early human tools, lifelike models of extinct human species such as Homo erectus and Homo floresiensis, and even a station allowing visitors to see what they would look like as a Neanderthal, the $20.7 million, 15,000-square-foot space is designed to allow visitors to explore exactly how humans became, well, human.

“It’s moving, it’s profound and it will change your ideas about what is humanity,” said Wayne Clough, secretary of the Smithsonian, adding that it “sets a new standard for future museum exhibits.”

The permanent exhibition is designed to take people along the course of human evolution through a multitude of interactive displays, including one that lets visitors travel to field sites where research is conducted. Much of the exhibit focuses on the specific ways in which humans have evolved — walking upright, making tools, controlling fire, eating meat, creating jewelry, burying the dead, developing agriculture and moving into cities.

Exhibit curators have taken particular care to show that our ancestors were real people, even if they looked a little different (read: hairier) than us. There is a full, lifelike reproduction of “Lucy,” the famous 3.2 million-year-old fossil of a Australopithecus afarensis specimen, for example. Several lifesize bronze statues and realistic busts of the various human species are also included, complete with facial muscles, teeth, eyes and freckles.

Not everything is interactive or a reproduction. Among the artifacts included in the exhibit are the two original fossil skulls of the Cro-Magnon and the La Ferrassie Neanderthal, the most complete skull of the species known in the world. On loan from the Musee de l’Homme in France, the pair of skulls will only be on display in Washington for three months.

Most of the exhibit’s other artifacts will remain, including the only original fossil Neanderthal skeleton in the United States. And officials say they plan to update the exhibition as new discoveries add to what scientists know about human evolution.

“It’s important for the public to see these finds and ask the relevant questions,” said Richard Potts, director of the Smithsonian’s Human Origins Program. “Our species has an amazing cultural history.”

The exhibition’s opening doesn’t come without controversy, however.

Some religious groups are upset the space is void of any reference to God. Smithsonian officials seemed to have known that criticism would come their way, addressing it head-on on the exhibition’s official Web site, where they note that the museum “encourages visitors to explore new scientific findings and decide how these findings complement their ideas.”

Meanwhile, some environmental activists are mad that a permanent space in the museum was named for David Koch, the CEO of Koch Industries Inc., a conglomerate whose holdings include commodities such as petroleum and natural gas. Greenpeace activists held a protest outside the museum on Wednesday, handing out fliers resembling a Old West “Wanted” poster alleging Koch and his business partner and brother, Charles, are deniers of global warming and are “fueling catastrophic climate change.”

Museum Director Cristian Samper dismissed the criticism, noting that public-private partnerships are necessary to fund the Smithsonian’s work.

Samper shared a story of how Koch once showed him ancient fossil ash that he personally recovered from an archeological dig in Tanzania. That shows Koch is personally interested in evolutionary research, Samper said, and that is the focus of the specific exhibit named in his honor.