A Vatican official said last week that theories of evolution -- or Darwinism -- fits just fine with Christianity, killing a crucial part of the argument for intelligent design.

For some time, propopents of intelligent design, also called creationism, have positioned their theory as the only one compatible with Christianity.

But Vatican Archbishop Gianfranco Ravasi, head of the Pontifical Council for Culture, said though the church has been historically hostile to Darwinism, they now have found the theory is traceable to St. Augustine and St. Thomas Aquinas, two of the more prominent theologians.

Father Giuseppe Tanzella-Nitti, Professor of Theology at the Pontifical Santa Croce University in Rome, said at a conference Wednesday that 4th century theologian St Augustine had "never heard the term evolution, but knew that big fish eat smaller fish" and forms of life had been transformed "slowly over time". Aquinas made similar observations in the Middle Ages.

The announcement comes about a month before a church-backed conference at Pontifical Gregorian University that will commemorate the 150th anniversary of Darwin's On the Origin of Species. At the conference, the Vatican plans to "play down" the idea of Intelligent Design, which argues a "higher power" must be responsible for the complexities of life. At the conference, theologians will brand intelligent design as a "cultural phenomenon, not a scientific or theological issue.