Analyze each of the following scientific reports, explaining how the pattern of the method of agreement is manifested by each. Discuss, in each case, the limitations of the method of agreement as applied to that quest for a causal connection.

Researchers from the National Cancer Institute announced that they have found a number of genetic markers shared by gay brothers, indicating that homosexuality has genetic roots. The investigators, reporting in Science, 16 July 1993, have found that out of 40 pairs of gay brothers examined in their study, 33 pairs shared certain DNA sequences on their X chromosome, the chromosome men inherit only from their mothers. The implicit reasoning of this report is that, if brothers who have specific DNA sequences in common are both gay, these sequences can be considered genetic markers for homosexuality.