Primates, which include humans, apes, monkeys and lemurs are diverse in traits like brain size, diet, locomotion and habitat. Using insights from recent advances in primate genomics and studying the DNA of over 500 primate species, scientists have uncovered the genetic secrets behind their evolutionary success and ecological flexibility.
A global team of scientists, including key researchers from the CSIR-Centre for Cellular and Molecular Biology’s LaCONES (Laboratory for the Conservation of Endangered Species) in Hyderabad, has made a breakthrough in understanding how primates have evolved over millions of years.
Led in India by Govindhaswamy Umapathy’s lab at CCMB-LaCONES, the research study explored how genetic changes shaped the variety seen across primates — from brain development and body size to diet, vision, movement and survival in extreme environments.
Primates have huge brains relative to their body size and the genes linked to brain development, such as those involved in neurogenesis and signalling pathways, show signs of rapid evolution in apes and monkeys. For example, Capuchin monkeys, which have the largest brain-to-body ratio after humans, possess genes under positive selection related to brain growth.
Body size also varies widely, from mouse lemurs (30 grams) to gorillas (200 kilograms). Genes like ‘DUOX2’ (linked to thyroid hormones) and growth hormone regulators (IGF genes) likely influenced size differences. Callitrichids (marmosets and tamarins) evolved smaller sizes through mutations in growth-related genes.
Early primates were nocturnal, but many groups shifted to daytime activity, so diurnal primates, like monkeys and apes, lost the reflective eye layer (‘tapetum lucidum’) for night vision but gained better colour vision. Trichromatic vision (seeing red, green and blue) evolved in Old World monkeys and apes through gene duplication. Howler monkeys independently developed this trait.
Nocturnal primates, like tarsiers and owl monkeys, have enlarged eyes and specialised genes for low-light vision. Smell declined in monkeys and apes, but remains critical for lemurs, which rely on scent for communication and finding food.
Adaptation
Gibbons, which swing through trees (brachiation), have genes linked to elongated limbs and cartilage development. Tarsiers, known for vertical leaping, carry genes affecting muscle growth and bone structure. Slow lorises, which move stealthily to avoid predators, have mutations in genes that reduce fast-twitch muscles, favouring energy-efficient movement. The loss of tails in apes and humans is tied to genetic changes and validated in mouse experiments.
Diet shaped genetic adaptations like the leaf-eating Colobine monkeys evolved stomachs for fermenting plants and duplicated RNASE1 genes to digest bacterial RNA. Insect-eating primates, like tarsiers, have extra copies of the ‘CHIA’ gene to break down insect exoskeletons. Bamboo lemurs and lorises expanded detoxification genes to process toxic plants. Taste receptors also adapted like fruit-eaters to detect sugars, while leaf-eaters sense bitter compounds to avoid toxins.
Primates in extreme environments showed unique genetic traits. Orangutans in food-scarce regions have genes linked to fat metabolism and muscle efficiency. Rhesus macaques in cold climates evolved larger bodies and genes for heat production. Snub-nosed monkeys living at high altitudes have mutations in genes for hypoxia response, etc. Limestone langurs in calcium-rich karst habitats adapted through genes that regulate calcium absorption and joint flexibility.
Interbreeding between species contributed to genetic diversity. Baboons in Tanzania inherited genes from three species, improving survival in arid conditions. Grey snub-nosed monkeys arose from hybridisation, blending coat colours from parent species. Adaptive gene flow introduced beneficial traits like immune genes in baboons and bitter-taste receptors in gorillas, aiding survival in new environments.
The research has revealed how genetic changes underpin the diversity of primates and helps understand the evolution and human origins, and steps needed to conserve these species, said Mr.Umapathy. The study, ‘Genomic Basis of Non-Human Primate Diversity and Adaptation’, was published in the latest edition of the Nature Reviews Biodiversity journal.
Published – April 15, 2025 02:08 am IST