AIM: To assess the extent to which humans have reshaped Earth's biodiversity, by estimating natural ranges of all late Quaternary mammalian species, and to compare diversity patterns based on these with diversity patterns based on current distributions. LOCATION: Globally. METHODS: We estimated species, functional and phylogenetic diversity patterns based on natural ranges of all mammalian species (n = 5747 species) as they could have been today in the complete absence of human influence through time. Following this, we compared macroecological analyses of current and natural diversity patterns to assess whether human‐induced range changes bias evolutionary and ecological analyses based on current diversity patterns. RESULTS: We find that current diversity patterns have been drastically modified by humans, mostly due to global extinctions and regional to local extirpations. Current and natural diversities exhibit marked deviations virtually everywhere outside sub‐Saharan Africa. These differences are strongest for terrestrial megafauna, but also important for all mammals combined. The human‐induced changes led to biases in estimates of environmental diversity drivers, especially for terrestrial megafauna, but also for all mammals combined. MAIN CONCLUSIONS: Our results show that fundamental diversity patterns have been reshaped by human‐driven extinctions and extirpations, highlighting humans as a major force in the Earth system. We thereby emphasize that estimating natural distributions and diversities is important to improve our understanding of the evolutionary and ecological drivers of diversity as well as for providing a benchmark for conservation.