Tuesday, February 19, 2019

Monkey Business: The Colonization of the South Asian Rainforest Was Accompanied by the Hunt For Monkeys

A new study provides for the first time direct evidence for the hunting of tree monkeys and other small mammals by the Homo sapiens 45,000 years ago in the rainforest of Sri Lanka.

A multidisciplinary study shows that as early as 45,000 years ago , Homo sapiens hunted small mammals in the forests of Sri Lanka. The research team discovered the remains of small mammals, including monkeys, at the oldest man-colonized archeological site in Sri Lanka , with traces of burn marks and burns alongside sophisticated bone and stone tools . The hunting of such animals is an example of the unique adaptability that enabled H. sapiens to rapidly colonize a number of extreme environments apparently unaffected by his hominin relatives.

Southern Hanuman langur ( S. priam ), one of the monkey species hunted by the people who settled the Fa Hien cave in Sri Lanka.
Credit:  © O. Wedage

An international research team led by the Jena Max Planck Institute for the History of Humanity reports in the journal Nature Communications on new findings on the unique adaptability of Homo sapiens . The study, which also involved scientists from Sri Lanka and other international institutions, shows that as early as 45,000 years ago, the inhabitants of the tropical rainforest of Sri Lanka had specialized in the hunting of small, agile mammals. This is the oldest and most comprehensive archaeological evidence to date for the demanding, active hunting of these prey by hunters and gatherers. The new study also highlights the pronounced capabilities of Homo sapiens to adapt to different habitats compared to other hominins.

The tropical rainforests: a unique challenge

Recent research has shown that as modern humans spread throughout the world, it has adapted to a variety of extreme habitats, including desert and high mountain regions, the paleo-arctic, and tropical rainforests. So far, however, the scientific discourse on global dispersal has focused mostly on increased efficiency in hunting, slaughter, and consumption of medium-sized to large game of open savannahs. In addition, coastal areas were considered an important source of proteins that favored human evolution and further spread.

Tropical rainforests, on the other hand, received less attention in the discussion. These habitats have been perceived by professionals to be obstacles to the spread of humans, posing particular challenges because of the presence of animals and diseases, and limited resources. In particular, compared to the large animals of the open savannah, small, agile tree monkeys and squirrels are difficult to catch and provide lower levels of protein.

Small mammals and the complexity of hunting

The hunting of small mammals has long been considered a feature of technological and behavioral "complexity" or "modernity" that is unique to our species. Earlier research in Europe and the Near East has linked the increasing capture and consumption of small mammals with both increasing populations and climatically induced crises.

However, in other parts of the world, especially in Asia and outside the temperate zones, the onset and nature of hunting for small mammals has been poorly understood. "Over the past two decades, research has shown that human colonization of tropical rainforests in South Asia, Southeast Asia and Melanesia began at least 45,000 years ago, making it likely that humans in that environment will already be feeding small mammals as food sources at this early stage ", says co-author Dr. Patrick Roberts from the Max Planck Institute for the History of Human History.

A special feature of Sri Lanka

The map shows the vegetation zones of Sri Lanka and the location of Fa-Hien Lena.
Credit: N. Amano. Wedage et al. 2019. Specialized rainforest hunting by Homo sapiens ~ 45,000 years ago. 

Credit: Nature Communications.

Sri Lanka plays a prominent role in the discussion of early human adaptation to tropical rainforests, although there is a general lack of systematic and detailed analysis of animal remains from archaeological sites on the island. The current study analyzed and dated animal remains and combinations of stone and bone tools of the Fa-Hien Lena cave using radiocarbon dating. Located in the middle of the tropical rainforest of Sri Lanka, it is the site of the oldest archaeological evidence for the presence of Homo sapiens in Sri Lanka.

"The results prove a demanding and specialized hunt for tree monkeys and other primates as well as squirrel already 45,000 years ago in the tropical rainforest", says first author Oshan Wedage of the Max Planck Institute for the History of Mankind. Co-author dr. Noel Amano adds: "This is also confirmed by the monkey bones tools that have been worked on using sophisticated techniques."

"Monkey Business"

The research results show a finely tuned focus in the hunt of monkeys and other small mammals. Thus, the findings point to a sustainable hunting strategy of Homo Sapiens , were hunted only adult animals, and thus the tropical rain forest was not over-exploited by the presence and practices of humans.

"Monkeys were part of the menu, and using this hard-to-reach resource is another example of the behavioral and technological flexibility of Homo sapiens, " says Prof. Michael Petraglia of the Max Planck Institute for Human History, one of the study leaders. Further analysis of the tools and animal remains left by the early members of our species also promises more detailed insights into the diversity of strategies that enabled Homo sapiens to colonize the continents of the world and survive as the only hominin species.

Contacts and sources:
Anne Gibson
The Max Planck Institute for the Science of Human History (MPI-SHH)
Citation: Specialized rainforest hunting by Homo sapiens ~ 45,000 years agoOshan Wedage, Noel Amano, Michelle C. Langley, Katerina Douka, James Blinkhorn, Alison Crowther, Siran Deraniyagala, Nikos Kourampas, Ian Simpson, Nimal Perera, Andrea Picin, Nicole Boivin, Michael Petraglia, Patrick Roberts

Neandertals’ Main Food Source Was Definitely Meat

Neandertals' diets are highly debated: they are traditionally considered carnivores and hunters of large mammals, but this hypothesis has recently been challenged by numerous pieces of evidence of plant consumption. Ancient diets are often reconstructed using nitrogen isotope ratios, a tracer of the trophic level, the position an organism occupies in a food chain. Neandertals are apparently occupying a high position in terrestrial food chains, exhibiting slightly higher ratios than carnivores (like hyenas, wolves or foxes) found at the same sites. It has been suggested that these slightly higher values were due to the consumption of mammoth or putrid meat. And we also know some examples of cannibalism for different Neandertal sites.

Tooth of an adult Neandertal from Les Cottés in France. Her diet consisted mainly of the meat of large herbivore mammals.
© MPI f. Evolutionary Anthropology/ A. Le Cabec

Paleolithic modern humans, who arrived in France shortly after the Neandertals had disappeared, exhibit even higher nitrogen isotope ratios than Neandertals. This is classically interpreted as the signature of freshwater fish consumption. Fishing is supposed to be a typical modern human activity, but again, a debate exists whether or not Neandertals were eating aquatic resources. When Klervia Jaouen, a researcher at the Max Planck Institute for Evolutionary Anthropology and first author of the study, and collaborators discovered high nitrogen isotope ratios in the collagen of two Neandertals falling in the range of modern humans, they wondered whether this could a signature of regular fish consumption.

The Neandertals come from Les Cottés and Grotte du Renne, in France, two sites where no fish remains have been found. However, the measurements were performed on a tooth root, which recorded the diet between four to eight years of the individual's life, and on a bone of a one-year-old baby. These high nitrogen isotope ratios could also indicate that the Neandertals were not weaned at this age, contradicting in the case of the Les Cottés Neandertal (the one whose tooth root was analyzed) former pieces of evidence of early weaning around one year of age. In other words, many explanations (e.g. freshwater fish consumption, putrid meat, late weaning or even cannibalism) could account for such high values, and identifying the factor involved could change our understanding of Neandertals' lifestyles.

Analysis of amino acids

In order to explain these exceptionally high nitrogen isotope ratios, Jaouen and collaborators decided to use a novel isotope technique. Compound-specific isotope analyses (CSIA) allow to separately analyze the amino acids contained in the collagen. Some of the amino acid isotope compositions are influenced by environmental factors and the isotope ratios of the food eaten. Other amino acid isotope ratios are in addition influenced by the trophic level. The combination of these amino acid isotope ratios allows to decipher the contribution of the environment and the trophic level to the final isotope composition of the collagen.

"Using this technique, we discovered that the Neandertal of Les Cottés had a purely terrestrial carnivore diet: she was not a late weaned child or a regular fish eater, and her people seem to have mostly hunted reindeers and horses", says Jaouen. "We also confirmed that the Grotte du Renne Neandertal was a breastfeeding baby whose mother was a meat eater". Interestingly, this conclusion matches with the observations of the zooarcheologists.

The study also illustrates the importance of this new isotope technique for future investigations into ancient human and Neandertal diets. Using compound-specific isotope analysis allowed the researchers not to misinterpret the global nitrogen isotope ratio which was exceptionally high. Michael P. Richards of the Simon Fraser University in Canada comments: "Previous isotope results indicated a primarily carnivorous diet for Neandertals, which matches the extensive archaeological record of animal remains found and deposited by Neandertals. There has recently been some frankly bizarre interpretations of the bulk isotope data ranging from Neandertals primarily subsisting on aquatic plants to eating each other, both in direct contrast to the archaeological evidence. These new compound-specific isotope measurements confirm earlier interpretations of Neandertal diets as being composed of mainly large herbivores, although of course they also consumed other foods such as plants."

Monotonous diet

In addition to confirming the Neandertals as terrestrial carnivores, this work seems to indicate that these hominins had a very monotonous diet over time, even once they had started to change their material industry, possibly under the influence of modern humans. The baby Neandertal of Grotte du Renne was indeed found associated to the Châtelperronian, a lithic technology similar to that of modern humans. Late Neandertals were therefore very humanlike, painting caves and wearing necklaces, but unlike their sister species, did not seem to enjoy fishing.

Jean-Jacques Hublin, director of the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology, comments: "This study confirms that when Homo sapiens arrived in Europe and met Neandertals, they were in direct competition for the exploitation of large mammals". "The systematic use of the combination of CSIA and radiocarbon dating will help to understand if the two species really had the same subsistence strategies during those crucial times", concludes Sahra Talamo, a researcher at the Leipzig Max Planck Institute.

Contacts and sources:
 .Sandra Jacob
 Max Planck Institute for Evolutionary Anthropology, Leipzig

Citation: Klervia Jaouen, Adeline Le Cabec, Frido Welker, Jean-Jacques Hublin, Marie Soressi, Sahra Talamo
Exceptionally high δ15N values in collagen single amino acids confirm Neandertals as high-trophic level carnivores
January 2019, DOI: 10.1073/pnas.1814087116