The subject - the place of humans in the universe - is a challenge. To the scientific way of thinking, humans no more have a "place" in the scheme of things than hamsters or harp seals. The universe itself may be an incomprehensible event, and life a so far unexplained one, but scientists see no ladder of creation with humans at the pinnacle. They can see no "purpose" in being. We are here because we are here, a lucky accident - lucky for us - but there was nothing inevitable about the evolution of humanity, or its survival. God is not part of the explanation.
That is how scientists have grown to think, whether they come from a religious background or not. But modern science did not emerge 400 years ago to challenge religion, the orthodoxy of the past 2,000 years. Generations of thinkers and experimenters and observers - often themselves churchmen - wanted to explain how God worked his wonders. Modern physics began with a desire to explain the clockwork of God's creation. Modern geology grew at least partly out of searches for evidence of Noah's flood. Modern biology owes much to the urge to marvel at the intricacy of Divine providence.
But the scientists - a word coined only in 1833 - who hoped to find God somehow painted Him out of the picture. By the late 20th century, physicists were confident of the history of the universe back to the first thousandth of a second, and geneticists and biochemists were certain that all living things could be traced back to some last universal common ancestor that lived perhaps 3.5bn years ago. A few things - what actually happened in the Big Bang, how living, replicating things emerged from a muddle of organic compounds - remain riddles. But few now consider these riddles to be incapable of solutions. So although the debate did not start out as science versus religion, that is how many people now see it.
Paradoxically, this is not how many scientists see it. In the US, according to a survey published in Nature in 1997, four out of 10 scientists believe in God. Just over 45% said they did not believe, and 14.5% described themselves as doubters or agnostics. This ratio of believers to non-believers had not changed in 80 years. Should anybody be surprised?