Cold climates led to longer maternal care among colobine monkeys

A groundbreaking study published in the journal Science presents a significant leap in our understanding of how environment shapes social behaviors. By studying colobine monkeys, the researchers discovered that adaptations to cold climates have a profound influence on the social evolution of species. 

Adaptations to cold climates seem to have been critical in facilitating enhanced motherly care, improved infant survival, and fostering the development of large, intricate multi level societies.

The study was conducted by a global team of researchers representing Northwest University in China, the University of Bristol in the UK, and the University of Western Australia. 

Focus of the study

The researchers set out to explore how langurs and odd-nosed monkeys from the Asian colobine family have evolved and adapted over time. These particular primates have found ways to thrive in environments ranging from tropical rainforests to snow-laden mountainous terrains.

According to the researchers, colobine monkeys have distinct types of social organizations. This presents an opportunity to analyze the various mechanisms which drive their social evolution. The experts wanted trace the evolutionary journey from a common ancestral state to the diverse social systems that these primates now exhibit.

What the researchers discovered 

By combining ecological, geological, fossil, behavioral, and genomic analyses, the scientists found that colobine primates dwelling in colder climates tend to form larger and more complex groups. The experts also determined that glacial periods over the last six million years have favored the selection of genes critical for cold-related energy metabolism and neuro-hormonal regulation.

Among the most remarkable discoveries was the adaptation exhibited by odd-nosed monkeys living in severely cold regions. These primates had developed hormonal pathways, specifically dopamine and oxytocin, which were not just more efficient but may also extend the duration of maternal care. This led to longer breastfeeding periods, and a significant increase in the survival rates of infants.

Such adaptive changes, researchers suggest, appear to have bolstered relationships among individuals, amplified male tolerance and ultimately precipitated the evolution from independent one-male, multi-female groups to large, complex, multilevel societies.

Significance of the study

“Our study identified, for the first time, a genetically regulated adaptation linked to the evolution of social systems in primates,” said Dr. Kit Opie from the Department of Anthropology and Archaeology at the University of Bristol.

“This finding offers new insights into the mechanisms that underpin behavioral evolution in primates and could be used to address social evolutionary changes across a wide range of species including humans.”

“In addition we would like to examine how changes in social and mating behavior in many primate species may be the result of genetic changes due to past environments as well as other social and environmental factors.”

Future implications

Dr. Cyril Grueter from the University of Western Australia emphasized the pressing urgency of climate change and its potential impact on animals. “With climate change becoming a hugely important environmental pressure on animals, it is hoped that this study will raise awareness for the need to investigate what course social evolution will take as the prevailing climate changes.” 

“Our finding that complex multilevel societies have roots stretching back to climatic events in the distant evolutionary past also has implications for a reconstruction of the human social system which is decidedly multilevel.”

More about Asian colobine monkeys 

The Asian colobine monkeys are a group of Old World monkeys belonging to the subfamily Colobinae, which is part of the family Cercopithecidae. The colobine monkeys are distinct from other Old World monkeys in a variety of ways, most notably their adaptation for a folivorous (leaf-eating) diet.

The monkeys are found throughout Africa and Asia, but the Asian colobines are a distinct group with several characteristic features. They are distinguished by their elongated bodies, long tails, and slender limbs. Most species are arboreal (tree-dwelling), and their physical features are adapted for a life in the trees. Their hands are elongated and dexterous, allowing them to adeptly handle leaves, their primary food source.

Asian colobine monkeys are known for their complex, multi-chambered stomachs, similar to those of cows. This adaptation allows them to ferment tough plant material, breaking down cellulose to extract nutrients. This is a critical adaptation for their leaf-eating diet, as leaves are generally low in energy and high in hard-to-digest fibers.

Well-known examples of Asian colobine monkeys

Langurs

These monkeys are often gray or black and live in social groups. One of the most famous is the Hanuman langur of India, named after the Hindu god Hanuman.

Leaf Monkeys 

These monkeys are known for their diverse coloration, ranging from golden to dark brown or black. The lutung, or dusky leaf monkey, is an example of this genus.

Snub-nosed monkeys 

These monkeys are characterized by their short noses with upward-facing nostrils. They are found in China, Vietnam, and parts of the Himalayas.

Proboscis monkeys 

Native to Borneo, these monkeys are best known for their large, pendulous noses, particularly pronounced in males.

Asian colobines are generally quite social, living in groups that can range from a few individuals to several dozen. They have complex social structures and behaviors, with both male and female hierarchies. Like many primate species, they use a variety of vocalizations and physical gestures to communicate with each other.

Many species of Asian colobines are under threat due to habitat loss, hunting, and the pet trade. They are often a focus of conservation efforts, as their loss can have significant impacts on the ecosystems they inhabit.

Image Credit: Guanlai Ouyang

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