A crucial assumption of evolutionary theories of aging is that age-specific differences of life history traits may have genetic causes. The present study focuses on the existence of such differences between eight freshly caught populations of Drosophila melanogaster. A highly significant differentiation of the populations is observed, yet it accounts for a relatively small part of the variance. It is also shown that large discrepancies may be found between the estimations of fitness based, on the one hand, on data for egg production and, on the other hand, on fertility data. This stresses the need for accurate measurements of fitness for the assessment of evolutionary theories. Finally, the results suggest that neither of the current evolutionary theories of aging is generally valid. Indeed, the age-specific differences that are found between the populations match either the antagonistic pleiotropy mechanism, or the concordant pleiotropy mechanism, or none of them.