Niche Construction Theory (NCT) has been gaining acceptance as an explanatory framework for processes in biological and human evolution. Human cultural niche construction, in particular, is suggested as a basis for understanding many phenomena that involve human genetic and cultural evolution. Herein I assess the ability of the cultural niche construction framework to meet this explanatory role by looking into several NCT-inspired accounts that have been offered for two important episodes of human evolution, and by examining the contribution of NCT to the elucidation of two "primary examples" mentioned often in the NCT literature. The result, I claim, is rather disappointing: While NCT may serve as a descriptive framework for these phenomena, it cannot be said to explain them in any substantive sense. Especially disturbing is NCT's failure to account for differing developments in very similar situations, and to facilitate evaluation and discrimination between divergent and contradictory causal accounts of particular phenomena. I argue that these problems are inherent, and they render NCT unsuitable to serve as an explanatory framework for human phenomena. NCT's value, at least as related to human phenomena, is therefore descriptive and heuristic rather than explanatory. In conclusion, I discuss and reject comparisons made between NCT and the theory of natural selection, and examine several potential sources of NCT's explanatory weakness.