Fruits of the forest: Human stable isotope ecology and rainforest adaptations in Late Pleistocene and Holocene (∼36 to 3 ka) Sri Lanka

Abstract

Sri Lanka has yielded some of the earliest dated fossil evidence for Homo sapiens (∼38-35,000 cal. years BP [calibrated years before present]) in South Asia, within a region that is today covered by tropical rainforest. Archaeozoological and archaeobotanical evidence indicates that these hunter-gatherers exploited tropical forest resources, yet the contribution of these resources to their overall subsistence strategies has, as in other Late Pleistocene rainforest settings, remained relatively unexplored. We build on previous work in this tropical region by applying both bulk and sequential stable carbon and oxygen isotope analysis to human and faunal tooth enamel from the sites of Batadomba-lena, Fa Hien-lena, and Balangoda Kuragala. Tooth enamel preservation was assessed by means of Fourier Transform Infrared Spectroscopy. We use these data to produce a detailed stable isotope ecology for Late Pleistocene-Holocene foragers in Sri Lanka from ∼36-29,000 to 3000 cal. years BP, allowing us to test the degree of human tropical forest resource reliance over a considerable time period. Given that non-human primates dominate the mammalian assemblages at these sites, we also focus on the stable isotope composition of three monkey species in order to study their ecological preferences and, indirectly, human hunting strategies. The results confirm a strong human reliance on tropical forest resources from ∼36-29,000 cal. years BP until the Iron Age ∼3 cal. years BP, while sequential tooth data show that forest resources were exploited year-round. This strategy was maintained through periods of evident environmental change at the Last Glacial Maximum and upon the arrival of agriculture. Long-term tropical forest reliance was supported by the specialised capture of non-human primates, although the isotopic data revealed no evidence for niche distinction between the hunted species. We conclude that humans rapidly developed a specialisation in the exploitation of South Asia's tropical forests following their arrival in this region.

Earliest Musa banana from the late Quaternary sequence at Fahien Rock Shelter in Sri Lanka

“…Macrofloral remains including seeds, epicarps, charcoal and wood, recovered from several rock shelter deposits in south‐west Sri Lanka, have been used to address archaeological issues such as subsistence models and in understanding depositional environments, although taphonomic processes may not have been considered in all cases (Deraniyagala, ; Kourampas et al ., ,; Perera, ; Perera et al ., ; Roberts et al ., , ). Phytoliths, however, have not been discussed in detail.…”

Calling all archaeologists: guidelines for terminology, methodology, data handling, and reporting when undertaking and reviewing stable isotope applications in archaeology

“…However, it is also important to note that although studies might document diagenetic alteration of isotopic ratios in certain archaeological materials and contexts (e.g. ), this does not mean that the same materials should not be analyzed in other settings . This has been a particular problem in stable carbon and oxygen isotope studies of tooth enamel, which have only recently begun to expand in archaeology following a period of distrust.…”

A transect of environmental variability across South Asia and its influence on Late Pleistocene human innovation and occupation

“…Vegetation models suggest that during the arid period of MIS 4 tropical forest extent would have been greatly reduced in the Wet Zone of the island (Ray and Adams, ; Boivin et al , ; Roberts et al , ). Firm evidence for vegetation change is in MIS 3 and MIS 2, however, where stable carbon and oxygen isotope evidence of fauna from the archaeological site of Batadomba‐lena suggests that the Wet Zone rainforests of the island were more open, between 36 000 and 12 000 cal a BP , in comparison to the present day (Roberts et al ., , ). This evidence is supported by a pollen record from the Horton Plains peat swamp and geomorphological record from Kitulgala Beli‐lena (Kourampas et al ., ) that characterize the LGM (24 000–18 500 cal a BP ) as progressively cooler and drier with significant grassland encroachment (Premathilake and Risberg, ; Premathilake, , ; Premathilake and Gunatilaka, ).…”

“…12 000 cal a BP ) through to the Iron Age ( c . 3000 cal a BP ) (Roberts et al ., , ). However, while changes in forest extent, particularly during MIS 2, clearly occurred, faunal, archaeobotanical, and molluscan evidence from the archaeological sites of Batadomba‐lena and Fa Hien‐lena (Perera, ; Perera et al , ), as well as direct stable isotope evidence from human fossil tooth enamel from Batadomba‐lena (Roberts et al ., , 2017), indicate the persistent human reliance on tropical forest resources, such as primates, other small semi‐arboreal mammals and trees, from 36 000 to 3000 cal a BP .…”