An initial study involved 80 undergrads spending five minutes thinking about either their fifteenth century ancestors, their great-grandparents or a recent shopping trip. Afterwards, those students in the two ancestor conditions were more confident about their likely performance in future exams, an effect that seemed to be mediated by their feeling more in control of their lives.
Three further studies showed that thinking or writing about their recent or distant ancestors led students to actually perform better on a range of intelligence tests, including verbal and spatial tasks (in one test, students who thought about their distant ancestors scored an average of 14 out of 16, compared with an average of 10 out of 16 among controls). The ancestor benefit was mediated partly by students attempting more answers – what the researchers called having a 'promotion orientation'.
The full account is here. I would like to see this replicated, and subject to more variation, but in the meantime it's an interesting idea.