The name of the game: palaeoproteomics and radiocarbon dates further refine the presence and dispersal of caprines in eastern and southern Africa.

We report the first large-scale palaeoproteomics research on eastern and southern African zooarchaeological samples, thereby refining our understanding of early caprine (sheep and goat) pastoralism in Africa. Assessing caprine introductions is a complicated task because of their skeletal similarity to endemic wild bovid species and the sparse and fragmentary state of relevant archaeological remains. Palaeoproteomics has previously proved effective in clarifying species attributions in African zooarchaeological materials, but few comparative protein sequences of wild bovid species have been available. Using newly generated type I collagen sequences for wild species, as well as previously published sequences, we assess species attributions for elements originally identified as caprine or 'unidentifiable bovid' from 17 eastern and southern African sites that span seven millennia. We identified over 70% of the archaeological remains and the direct radiocarbon dating of domesticate specimens allows refinement of the chronology of caprine presence in both African regions. These results thus confirm earlier occurrences in eastern Africa and the systematic association of domesticated caprines with wild bovids at all archaeological sites. The combined biomolecular approach highlights repeatability and accuracy of the methods for conclusive contribution in species attribution of archaeological remains in dry African environments.

Reductions in the dietary niche of southern sea otters (Enhydra lutris nereis) from the Holocene to the Anthropocene.

The sea otter (Enhydra lutris) is a marine mammal hunted to near extinction during the 1800s. Despite their well-known modern importance as a keystone species, we know little about historical sea otter ecology. Here, we characterize the ecological niche of ancient southern sea otters (E. lutris nereis) using δ13C analysis and δ15N analysis of bones recovered from archaeological sites spanning ~7,000 to 350 years before present (N = 112 individuals) at five regions along the coast of California. These data are compared with previously published data on modern animals (N = 165) and potential modern prey items. In addition, we analyze the δ15N of individual amino acids for 23 individuals to test for differences in sea otter trophic ecology through time. After correcting for tissue-specific and temporal isotopic effects, we employ nonparametric statistics and Bayesian niche models to quantify differences among ancient and modern animals. We find ancient otters occupied a larger isotopic niche than nearly all modern localities; likely reflecting broader habitat and prey use in prefur trade populations. In addition, ancient sea otters at the most southerly sites occupied an isotopic niche that was more than twice as large as ancient otters from northerly regions. This likely reflects greater invertebrate prey diversity in southern California relative to northern California. Thus, we suggest the potential dietary niche of sea otters in southern California could be larger than in central and northern California. At two sites, Año Nuevo and Monterey Bay, ancient otters had significantly higher δ15N values than modern populations. Amino acid δ15N data indicated this resulted from shifting baseline isotope values, rather than a change in sea otter trophic ecology. Our results help in better understanding the contemporary ecological role of sea otters and exemplify the strength of combing zooarchaeological and biological information to provide baseline data for conservation efforts.

The shifting baseline of northern fur seal ecology in the northeast Pacific Ocean.

Historical data provide a baseline against which to judge the significance of recent ecological shifts and guide conservation strategies, especially for species decimated by pre-20th century harvesting. Northern fur seals (NFS; Callorhinus ursinus) are a common pinniped species in archaeological sites from southern California to the Aleutian Islands, yet today they breed almost exclusively on offshore islands at high latitudes. Harvest profiles from archaeological sites contain many unweaned pups, confirming the presence of temperate-latitude breeding colonies in California, the Pacific Northwest, and the eastern Aleutian Islands. Isotopic results suggest that prehistoric NFS fed offshore across their entire range, that California populations were distinct from populations to the north, and that populations breeding at temperate latitudes in the past used a different reproductive strategy than modern populations. The extinction of temperate-latitude breeding populations was asynchronous geographically. In southern California, the Pacific Northwest, and the eastern Aleutians, NFS remained abundant in the archaeological record up to the historical period approximately 200 years B.P.; thus their regional collapse is plausibly attributed to historical hunting or some other anthropogenic ecosystem disturbance. In contrast, NFS populations in central and northern California collapsed at approximately 800 years B.P., long before European contact. The relative roles of human hunting versus climatic factors in explaining this ecological shift are unclear, as more paleoclimate information is needed from the coastal zone.

Holocene changes in the ecology of northern fur seals: insights from stable isotopes and archaeofauna.

The remains of northern fur seals (Callorhinus ursinus) are among the most abundant of pinniped elements recovered from mainland coastal archaeological sites in both California and Oregon. This is surprising as all contemporary northern fur seals breed exclusively on offshore islands, primarily at high latitudes, and the species is otherwise pelagic. The vulnerability of these animals to human predation suggests that either humans were foraging much further offshore than has been presumed or alternatively that the ecology of these animals has shifted during the late Holocene. We used isotopic and archaeofaunal analysis of the remains of pinnipeds from the middle to late Holocene of central and northern California to clarify the breeding and foraging behavior, and migration patterns of these ancient animals. The carbon and nitrogen isotope compositions of ancient northern fur seals reveal that these animals fed as far offshore as they do today, and that they remained at middle latitudes throughout the year. From an archaeological site at Moss Landing, California, we identified 16 skeletal elements from at least 12 very small northern fur seal pups. From another site near Mendocino, California, we identified the remains of at least 6 pups. We estimate the size and age of 5 of the young animals using sex-specific regressions of body length on the short dentary length derived from measurements of modern specimens. Our estimates indicate these ancient pups were substantially smaller, and therefore younger, than modern 3-month-old northern fur seal pups from similar latitudes and their nitrogen isotope compositions suggest they had not been weaned. As present-day northern fur seals do not leave their rookeries until they are at least 4 months old, we consider it highly unlikely that these ancient pups swam to these mainland locations from some distant island rookery. While there are numerous nearshore rocky outcrops along the Mendocino Coast, which may have supported small breeding colonies, the Moss Landing site is centered on a 40-km-long sandy beach, and is more than 120 km from what at the time were the nearest offshore islands. We conclude that northern fur seal adult females, subadults, and pups whose remains were recovered at the Moss Landing archaeological site must have been taken at a mainland rookery. Evidence that northern fur seals once bred on the mainland at this central California location suggests that the abundant remains of these animals at numerous other archaeological sites along the California coast also reflect the presence of nearby mainland rookeries. Based on the relative abundance of their remains in ancient human occupation sites and the widespread distribution of sites where their remains have been found, it appears that northern fur seals were once the predominant pinniped throughout a region where they now only rarely occur. Furthermore, their presence along the central and northern California coasts appears to have once severely limited the distribution of other pinnipeds, which are now common to the region.