Bringing hominins back to life

Today's issue of Science features a four-page article by yours truly about the "paleoartists" who create lifelike, three-dimensional models of human ancestors for museums, magazines, and documentaries. The story, which unfortunately is available only to paying subscribers, is chocked full of great photos provided by several of the artists whose work we profile. You can, however, click on this free link and listen to a Podcast in which I talk about the paleoartists and what they do.

Here are a few excerpts from the story that I hope will get you interested:

The interplay between art and science makes reconstruction "a two-way street," says Gary Sawyer, who has been reconstructing hominins at the American Museum of Natural History (AMNH) in New York City for more than 30 years. The artists must track researchers' latest anatomical interpretations, and reconstruction helps scientists think about issues such as "what kind of muscles a hominin had and how it walked on the landscape," says Alemseged. "But the end product should be seen as an artistic creation."

Some researchers argue that reconstructions influence how scientists view ancient hominins and interpret their behavior. "The scientific community requires a lengthy period of time to absorb and adapt to new ideas, and these illustrations are often part of the process by which you see the change," says Stephanie Moser, an archaeologist at Southampton University in the United Kingdom. "These artistic representations are part of the knowledge cycle and not outside it."

And how are they made?

Whether the art influences the science, the artists work hard to insure that science drives their creations. Each job is unique, but paleoartists usually start with plaster or urethane skull casts of a hominin; for fragile or incomplete skulls, they use computed tomography scans to create a "virtual" plastic cast. Then the artists painstakingly model the muscles, glands, and fat tissues of the face with clay, making educated guesses about how thick each tissue should be and guided by dissections of primates and forensic anthropology techniques. After making a new cast in urethane or acrylic plastic, the paleoartist then painstakingly inserts individual hairs, often from humans, and paints and makes up the face. A similar process is followed with the rest of the body, for which the thickness of skeletal bones and the depth of muscle insertions guide the artists as they decide how slim or stocky to craft the body.

But the paleoartists often have to cross the line between art and science:

Adrie Kennis, who with Alfons has created many hominin reconstructions for European museums, says such compromises are necessary. "If only the scientists made the reconstructions, they would be dull. ... We have to put a character on the face." For example, one key decision paleoartists face is whether to color the sclera of hominin eyes white, as in modern humans, or dark, as in many primates. In modern humans, eye whites make it easier for us to see where our fellow humans are gazing, thus enhancing social communication. But researchers know nothing about the sclera of earlier hominins. "It's a soft tissue we have no data on," says Potts, who adds that he and Gurche discussed at length how to handle the eyes of Gurche's sculptures for the human evolution hall.

Another issue is whether to put smiles on the ancient faces. "The fear muscles in great apes were coopted for smile muscles in humans. We've gone back and forth, how much should they grimace and how much should they smile." In the end, Potts says, they have often gone for a neutral, "almost Mona Lisa kind of effect."

By the way, you might notice that at Science we have begun using the newer and more scientifically correct name for humans and their ancestors, hominin, rather than the older word hominid, which actually refers to humans and great apes.

Photos: A female Neandertal, nicknamed "Wilma," created by Adrie and Alfons Kennis for the cover of National Geographic; Elisabeth Daynès in her Paris studio; John Gurche working on a model of Homo erectus for the Museum of the Earth outside Ithaca, New York.