Interpreting the Effects of Cultural Filtering.

Our results clearly show that the multiple filtering effects of sociocultural processes have been the main drivers of the distributions of the studied megafauna taxa over the past 2 millennia in eastern China (Table 1), a period during which agriculture has been the foundation for both individual livelihoods and overall society (32). First, at the individual behavior level, land-use expansion for agriculture, which is culturally learned, was confirmed to consistently reduce the ranges of all five megafauna taxa at the large spatiotemporal scale studied, consistent with our expectation that habitat loss due to agriculture is one of the major threats to mammal diversity. Human-induced habitat loss is a long-established major driver of regional and global megafauna declines throughout the Holocene and in the Anthropocene (19, 33, 34). Similarly, many freshwater species have been extirpated due to land reclamation of wetlands in the study region (35).

Second, at the level of cultural microevolution, increasing societal complexity and technical productivity, partly reflected by agricultural intensification, were estimated to have had mixed effects on megafauna distributions. On the one hand, higher societal complexity associated with human population growth (36) usually places extra demands on natural resources, including various ecosystem provisioning services, resulting in pressure on the local presence of some taxa (30), in line with our findings (in Fig. 3, compare the shapes of the curves for a particular taxon among the three agricultural intensity levels). On the other hand, increased cropland productivity due to intensive agricultural technologies was also confirmed to reduce the per-unit human population-growth effects on the five megafauna taxa, suggesting that agricultural intensification may partially alleviate per-capita ecological impacts (Fig. 3; the probability of megafauna presence at high human-population densities is greater under annual or multiple cropping than for fallow-based agriculture).

Fig. 3. Probability of the local (scale of 100 × 100 km) presence of five megafauna taxa estimated with the models in Table 1. Solid lines indicate taxa that have only a single lowest BIC model in Table 1, while point–dash and dashed lines indicate taxa that have two effectively equally lowest BIC models in Table 1. Modeling and plotting were implemented in R software (76) using the bife package (75).

However, the coefficients of the population-density term in Table 1 are always negative, even for annual or multiple cropping, indicating that agricultural intensification in Imperial China did not arrest agricultural land expansion into the habitats of the five taxa, inconsistent with the “land-sparing” hypothesis (28). Moreover, the finding shown in Table 1 that the coefficient of multiple cropping for each taxon is larger than that of annual cropping suggests that sociocultural changes associated with agricultural intensification can intensify the impacts on megafauna distributions at these broad scales. Therefore, cultural microevolution represented by agricultural intensification had overall negative filtering effects on the megafauna taxa in eastern China, representing transformation from biodiverse natural landscapes into productive croplands (19, 22). In ancient Egypt, millennia-long societal changes in response to aridification, with intensifying resource exploitation, were also associated with extirpations of many large-bodied mammal species (37). Importantly, in industrialized societies, urbanization and land-use intensification are major socioeconomic drivers of farmland abandonment (14, 38) and thus have the potential to provide both food security and nature recovery, including the return of locally extinct mammal species (39⇓–41).

Third, simple, direct cultural filtering by Han vs. non-Han cultural groups was found only for the Asiatic elephant, although interactive effects of the Han culture with other drivers were found for some of the other taxa (Table 1). Notably, the tiger also shows distinct probability curves in response to Han vs. non-Han cultural groups (Fig. 3); however, this effect was not well estimated during the model fitting (SI Appendix, Supplementary text). Although the spread of the Han culture has resulted in intensified local land use for farming and reshaped natural landscapes (22, 42), no explicit evidence is available to suggest that the Asiatic elephant is particularly sensitive to the Han culture, as there are historical records showing that both Han and non-Han cultural groups hunted the Asiatic elephant for tusks or meat and as a nuisance species (24), with human–elephant conflicts also reported elsewhere around the world (43). However, it is important to note that agriculture has played a more important role in the Han culture than in non-Han cultures in China (32) and thus should be considered to have a greater influence on activities and factors shown to be detrimental to crop production. Hence, it is sensible to argue that conflicts between Han societies and wildlife are likely to have been stronger, especially those involving herbivores that damage crops, with the Asiatic elephant providing evidence for cultural macroevolutionary filtering (see narratives in ref. 24 for past conflicts between Han Chinese and the Asiatic elephant). Similar filtering effects on biodiversity can also be found in the Brazilian Amazon (44) and tropical northern Australia (45), where lands inhabited by indigenous, less agricultural people are subject to lower biodiversity losses than other inhabited lands.

Furthermore, as shown in Fig. 2, the spread of the Han culture was generally concurrent with agricultural intensification from low intensity to intermediate or high intensity, likely due to the focus of the Han culture on crop production. Hence, in Table 1, the two positive coefficients of the population-density–cultural group interaction (PD×CG) term for the Asiatic elephant and tiger and the two negative coefficients of the annual cropping–cultural group interaction (AC×CG) term for rhinoceroses and the brown bear are reflections of the cross-level link (the horizontal spread of microevolution associated with macroevolution) between the Han culture and intensive agricultural production: When the Han culture is present (CG = 1), intensive agriculture (e.g., annual cropping) becomes widespread and has the 2-fold effects on megafauna discussed above—the negative effects associated with agricultural intensification (reflected by the negative AC×CG term) and the alleviation of per-unit population growth effects on megafauna (reflected by the positive PD×CG term). Indeed, it is not uncommon for cultural or ethnic groups to spread at the expense of others, with newly arriving cultures reshaping previous culture–nature relationships and, by extension, nature (20, 21). For example, the global spread of H. sapiens, characterized by cultural evolution (13), has been argued to be the main driver of the late Quaternary megafauna extinction, reshaping continental megafauna communities that in some cases had coexisted with other hominins across long time spans (2). Changes in fire regimes and biotic interactions caused by European settlement in Australia have led to an extraordinary rate of mammal extinction, at least partly coupled to the loss of Aboriginal culture (46). Analogously, large carnivores and ungulates in North America have experienced notable range contractions since European settlement (16).