That number has remained unchanged for the past 30 years, since 1982, when Gallup first asked the question on creationism versus evolution. Thirty years ago, 44% of the people who responded said they believed that God created humans as we know them today - only a 2-point difference from 2012.
"Despite the many changes that have taken place in American society and culture over the past 30 years, including new discoveries in biological and social science, there has been virtually no sustained change in Americans' views of the origin of the human species since 1982," wrote Gallup's Frank Newport. "All in all, there is no evidence in this trend of a substantial movement toward a secular viewpoint on human origins."
The second most common view is that humans evolved with God's guidance - a view held by 32% of respondents. The view that humans evolved with no guidance from God was held by 15% of respondents.