Darwinian evolution is accepted by the great majority of scientists as the method by which the diversity of earth's organisms, including humans, evolved. Current research continues to expand our knowledge of evolutionary mechanisms. However, certain religious groups, supporting teaching the creation of earth's species as outlined in Genesis ("Creationism"), challenge in US courts teaching only Darwinian evolution in biology classes. The Courts must decide whether teaching creationism violates the Constitution's First Amendment prohibiting government "establishment of religion". In a 2005 challenge (US District Court, Pennsylvania), a local school board mandated a disclaimer be read to biology classes stating there were gaps in Darwin's theory and that "Intelligent Design" (ID), propounded as science, provided a different explanation of life's origins. ID proposes that many living structures exhibit "irreducible complexity", could not have evolved via natural selection and, therefore, exhibit evidence of an intelligent designer. After expert testimony, the judge ruled (12/05) that ID was a form of religion, a modernized concept of creationism, and should not be taught in biology classes because it violated US and Pennsylvania Constitutions. Similar challenges to teaching Darwinian evolution are occurring in at least nine other US states.