My dissertation is on the philosophical implications of niche construction for the concept of fitness and the scope of natural selection explanations. In these two months, I will be working on two companion manuscripts. The first is against a widely held philosophical interpretation of fitness— the Propensity Interpretation of Fitness (PIF). PIF reduces population fitness values to individual propensities. Based on the variability of local niche construction, I argue that individual propensities cannot ground population-level fitness rankings. In the second paper, I argue that current debates on the consistency of niche construction with Adaptationism overlook a particular type of challenge from niche construction. Adaptationism assumes a "one population- one niche” dogma: a single population of variants is encountered with a single set of environmental challenges. The variation of individual niches, however, creates multiple sets of challenges for a single population of variants. The applicability of natural selection under these cases shows that the lack of a single set environmental cause for evolution is not a reason to exclude natural selection explanations.