Cosmological anomalies and exotic smoothness structures

It seems to be generally accepted that apparently anomalous cosmological observations, such as accelerating expansion, etc., necessarily are inconsistent with standard general relativity and standard matter sources. Following the suggestions of S{\l}adkowski, we point out that in addition to exotic theories and exotic matter there is another possibility. We refer to exotic differential structures on ${\mathbb{R}}^4$ which could be the source of the observed anomalies without changing the Einstein equations or introducing strange forms of matter.