Palaeoenvironments and hominin evolutionary dynamics in southeast Asia

Abstract

Secure environmental contexts are crucial for hominin interpretation and comparison. The discovery of a Denisovan individual and associated fauna at Tam Ngu Hao 2 (Cobra) Cave, Laos, dating back to 164-131 ka, allows for environmental comparisons between this (sub)tropical site and the Palearctic Denisovan sites of Denisova Cave (Russia) and Baishiya Karst Cave (China). Denisovans from northern latitudes foraged in a mix of forested and open landscapes, including tundra and steppe. Using stable isotope values from the Cobra Cave assemblage, we demonstrate that, despite the presence of nearby canopy forests, the Denisovan individual from Cobra Cave primarily consumed plants and/or animals from open forests and savannah. Using faunal evidence and proxy indicators of climates, results herein highlight a local expansion of rainforest at ~ 130 ka, raising questions about how Denisovans responded to this local climate change. Comparing the diet and habitat of the archaic hominin from Cobra Cave with those of early Homo sapiens from Tam Pà Ling Cave (46-43 ka), Laos, it appears that only our species was able to exploit rainforest resources.

Figure 1

(a) Location of key sites of Denisovans in Russia (Denisova Cave), China (Baishiya Karst Cave), and Laos (Tam Ngu Hao (Cobra) Cave). The yellow line represents the biogeographic limit between the Palearctic and Oriental realms. (b) Location of the southeast Asian mammalian assemblages used in the study: Tam Pà Ling, Tam Hang South, Nam Lot, Tam Hay Marklot, and Tam Ngu Hao (Cobra) in northeastern Laos; Coc Muoi and Duoi U’Oi in Vietnam. Only three sites produced hominin remains: Tam Ngu Hao (Cobra) Cave (Denisovan, 164–131 ka), Tam Pà Ling (H. sapiens, 86–43 ka), and Duoi U’Oi (Homo sp., 70–60 ka) [Source: (a) Base map from https://capcarto.fr, (b) Authors].

Figure 2

(a) Distribution of δ¹³C_{carbon source} values of animal and Denisovan specimens from Cobra Cave by taxon (see “Material and methods” for range of values associated with biomes). (b) Histogram distribution of the relative frequency (%) in δ¹³C_{carbon source} values for all taxa. Each bin represents a spacing of 1%. The dashed red line refers to the mean value (Source: Authors).

Figure 3

Distribution of δ¹³C_{carbon source} values of ungulate and hominin specimens from two sites (see “Material and methods” for range of values associated with biomes): Tam Ngu Hao (Cobra) Cave (Denisovan TNH2-1, 164–131 ka) (Supplementary Annex S1) and Tam Pà Ling (Homo sapiens TPL-1, 46–43 ka) (Supplementary Annex S2) (Source: Authors).

Figure 4

Distribution of δ¹³C_{carbon source} and δ¹⁸O values for all taxa in the southeast Asian faunas (Supplementary Annexes S1, S3, S4) from Tam Hay Marklot, Duoi U'Oi, Nam Lot, Tam Hang South, Coc Muoi, and Tam Ngu Hao (Cobra) Cave (this paper). All sites were found within a relatively narrow latitudinal belt between 23° and 20° running through the northern regions of Laos and Vietnam (Fig. 1). The sites follow a chronological order from left to right highlighting environmental changes through vegetation cover variation (δ¹³C_{carbon source}) and likely rainfall regimes (δ¹⁸O). The outline of the violin plots represents kernel probability density, where the width shows the proportion of the data found there. The boxes from the box and whisker plots inside the violin represent the 25th–75th percentiles, with the median as a bold horizontal line (Source: Authors).

Figure 5

(a) Chinese caves δ¹⁸O records (left ordinate axis, ‰ VPDB International Standard Vienna Pee Dee Belemnite) showing millennial-scale climate shifts related to changes in East Asian summer monsoon intensity for the last 224 ka (black line) published in 2008 by Wang et al.. Numbers refer to the marine isotope stages and substages. The right ordinate axis corresponds to the Northern Hemisphere summer insolation (red line) (65°N, W m⁻²). (b) Histograms of faunas showing the distribution of δ¹³C_{carbon source} values of specimens associated with each biome (Supplementary Table S5). (c) Age ranges of faunas: Tam Ngu Hao (Cobra) Cave (MIS 6.3, 164–131 ka) analyzed herein, Coc Muoi (MIS 6.2, 148–117 ka), Tam Hang South (MIS 5, 94–60 ka), Nam Lot (MIS 5, 86–72 ka), Duoi U’Oi (MIS 4, 70–60 ka) and Tam Hay Marklot (MIS 3–2, 38.4–13.5 ka). (d) Occurrence of hominins in the region, Denisovan (Cobra Cave, 164–131 ka), Homo sp. (Duoi U’Oi, 70–60 ka) and H. sapiens (Tam Pà ling, 86–43 ka) [Source: (a) Modified from Wang et al.; (b–d) Authors].

Figure 6

Compared biodiversity between Duoi U’Oi (MIS 4, 70–60 ka) and Tam Hay Marklot (MIS 3–2, 38.4–13.5 ka) faunas. We combined in a same scheme the 3 descriptors of biodiversity, species diversity among identified ruminant taxa (i.e., cervids and bovids being able to browse and/or graze, Supplementary Tables S2, S3), species abundance (by using percentages of the minimum number of individuals (MNI), Supplementary Tables S12), and distribution of ecological niches (biome associated with each taxon) (Source: Silhouette image from public domain https://www.phylopic.org; charts, Authors).