For the following question, arrange the sentences A, B, C, and D between sentences 1 and 6 to form a logical sequence with sentence 1 and sentence 6 as the starting sentence and the concluding sentence respectively:
(1) Man has existed for about a million years.
(P) Science, as a dominant factor in determining the beliefs of educated human beings, has existed for about 300 years and as a source of economic technique for about 150 years.
(Q) When we consider how recently it has risen to power, we find ourselves forced to believe that we are at the very beginning of its contribution to transforming human life.
(R) In this brief period, it has proved itself as an incredibly powerful revolutionary force.
(S) He has possessed writing for about 6000 years, and agriculture for perhaps just a little longer.
(6) What its future effects will be is a matter of conjecture, but possibly a study of its effects up till now may make the conjecture a little more meaningful.