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.