Fig. 1. Habitat quality map for early Homo (EHS, left) and modern human species (MHS, right). The maps show the quality of the habitats potentially suitable to human occupation for the common ancestors of EHS and MHS, respectively. Quality varies from little (blue) to highly suitable (red) areas. The fossil occurrences of EHS (H. habilis, H. ergaster and H. erectus ) and MHS (H. heidelbergensis, H. neanderthalensis and H. sapiens ) are superimposed on each map (pink dots).
Despite the enormous geographic variation in both the preservation potential and the intensity of paleontological sampling24, our data suggest the existence of a strong association between habitat quality and the presence of fossil remains, either for EHS (Area Under The Curve (AUC) = 0.80, Fig. 1 left, AUC after subsampling the most abundant species = 0.71) or MHS (AUC = 0.81, Fig. 1 right, AUC after subsampling the most abundant species = 0.82). This strong association remains true for all nodes in the hominin tree (Extended Data Figs. 1, 2 Extended Data Tables 1, 2) and suggests that climatic variation in time and space determined the geographic ranges of our ancestors. Excluding extreme climatic values in order to mitigate the effect of potential paleoclimatic errors in the paleoclimate emulator (i.e. excluding the climatic records beyond the 90th percentile of the individual variable distribution), the AUC value for EHS decreases to 0.68, whereas it increases to as much as 0.82 for MHS (Extended Data Table 3, Extended Data Fig. 3). In contrast, repeating this test by randomly sampling the same number of point occurrences per species throughout the biogeographical domain of individual species (Extended Data Table 4, Extended Data Fig. 4) leads to a much weaker association between occurrences and climatic suitability (EHS AUC = 0.56 95%, confidence interval: 0.52-0.61; MHS AUC = 0.58, confidence interval: 0.56-0.60). This test indicates that a random placement of fossil localities within the biogeographic domain of the species leads to non-significant association between fossil remains and climatic conditions, thereby strengthening the notion that the geographic position of archaeological sites is a non-random process guided by climatic variability.