Paper No. : 14 Human Origin and Evolution Module : 09 Classification and Distribution of Living Primates Development Team Principal Investigator Prof. Anup Kumar Kapoor Department of Anthropology, University of Delhi Dr. Satwanti Kapoor (Retd Professor) Paper Coordinator Department of Anthropology, University of Delhi Mr. Vijit Deepani & Prof. A.K. Kapoor Content Writer Department of Anthropology, University of Delhi Prof. R.K. Pathak Content Reviewer Department of Anthropology, Panjab University, Chandigarh 1 Classification and Distribution of Living Primates Anthropology Description of Module Subject Name Anthropology Paper Name Human Origin and Evolution Module Name/Title Classification and Distribution of Living Primates Module Id 09 Contents: Primates: A brief Outline Classification of Living Primates Distribution of Living Primates Summary Learning Objectives: To understand the classification of living primates. To discern the distribution of living primates. 2 Classification and Distribution of Living Primates Anthropology Primates: A brief Outline Primates reside at the initial stage in the series of evolution of man and therefore constitute the first footstep of man’s origin. Primates are primarily mammals possessing several basic mammalian features such as presence of mammary glands, dense body hair; heterodonty, increased brain size, endothermy, a relatively long gestation period followed by live birth, considerable capacity for learning and behavioural flexibility. St. George J Mivart (1873) defined Primates (as an order) as "unguiculate, claviculate, placental mammals, with orbits encircled by bone; three kinds of teeth, at least at one time of life; brains always with a posterior lobe and calcarine fissure; the innermost digits of at least one pair of extremities opposable, hallux with a flat nail or none; a well-developed caecum; pendulous penis; testes with scrotum; two pectoral mammae." Thus following characteristics differentiate primates, as a group, from other mammals: (Swindler, 2004; Jurmain et al., 2012) Prehensile limbs, Pentadactyly and Flattened Nails Either thumb or great toe is opposable or both are opposable Presence of well developed clavicle Fingers and toe possess sensitive tactile pads (enriched with sensory nerve fibers) at the ends of digits Generalized dentition Orbits surrounded by bony rims, enhancement in visual depth perception, binocular vision Increase in size and complexity of the brain Primates possess two pectoral mammae, efficient means of fetal nourishment, longer gestation times. Primates possess pendulous penis Diurnal activity pattern (except some prosimians, new world monkey) Tendency to reside in social groups 3 Classification and Distribution of Living Primates Anthropology Classification of Living Primates The term classification is often used interchangeably with terms ‘systematics’ and ‘taxonomy’. Simpson (1961) defined Systematics as the scientific study of the kinds and diversity of organisms and of any and all relationships among them. Systematics provides insight into the evolutionary relationships between organisms and taxonomy deals with classification and nomenclature of organisms. The key (groups different organisms together if they share one striking character), the Phenetic (or natural – groups organisms in accordance to their degree of overall resemblance often in morphology or other observable features, regardless of their phylogeny or evolutionary relation) and the Phyletic (or phylogenetic – attempts to group organisms in accordance to their evolutionary relationships) – constitute three major types of classification. Swedish naturalist Carl Linnaeus had made pivotal contribution to the present hierarchial classification of animals. Kingdom, phylum or division, class, order, family, genus, species- are seven major taxonomic ranks and species (or biological species) is designated as the basic unit of classification. Thus classification of primates simply implies ordering of primates into groups on the basis of their relationship to each other though descent from a common ancestor. The prime motive of any classification is therefore to develop a hierarchical system of categories of increasing rank. The term ‘Primates’ was first used by Carolus Linnaeus to encompass four genera: Homo (man), Simia (all monkeys and apes of the Old world and New world then known), Lemur and Verspetilio (bats) and later bats were removed from the order (Swindler, 2004). In 1971, J. F. Blumenbach proposed a primate classification where he categorized primates into two orders, Binama (included man) and Quadrumana (included apes, monkeys and lemurs) (Shukla and Rastogi, 2011). The classification was not accepted worldwide. 4 Classification and Distribution of Living Primates Anthropology Fig I: Taxonomic classification of animals (Source: Lewis et al., 2007). Figure I depicts classification scheme of animals and thus the taxonomic specification of order Primate can be represented as: Category Taxon Kingdom Animalia Subkingdom Metazoa Phylum Chordata Subphylum Vertebrata Class Mammalia Order Primates G.G. Simpson in 1945 proposed a primate classification, whereby the morphological resemblance among the primate species was utilized as basic and sole criteria of classification. His classification 5 Classification and Distribution of Living Primates Anthropology proposal was comparatively simple. He differentiated man (Hominidae) from apes (Pongidae) at family level and classified australopithecines (hominins) with pongids and if the morphological resemblance exhibits evolutionary relationship, then the traditional classification emphasized that hominid branch was first to separate from pongids which later differentiated into all extant ape genera and species (Ayala and Cela-conde,2017). Figure II (below) exhibits the classification of living primates. The order primate order is a part of a larger group, the class Mammalia (phylum Chordata). The former is categorized into two traditional suborders, namely, categories, Prosimii (all the prosimians: lemurs, lorises, and, customarily, the tarsiers) and Anthropoidea (all the monkeys, apes, and humans). An important point to be emphasized here is that the suborder distinction is more specific than the order (Jurmain et al., 2012). At the suborder level, the prosimians form a separate group which is different from all the other primates. The above statement is biological and evolutionary relevant. Similarly, all anthropoid species are more closely linked to each another than they are to the prosimians. An alternative classification scheme was also supported by certain section of Primatologists in which tarsiers and anthropoids were grouped in the suborder Haplorhini and lemurs, lorises and galagos were placed in suborder Strepsirhini (Ayala and Cela-conde, 2017). The anatomy of the nose was the base of this classification as the nose of strepsirhine primates is composed of a moist rhinarium and a lateral slit or crease (‘strepsis’ meaning twisting) and the nose of haplorhine primates lacked moist rhinarium (‘haplos’ meaning simple and unadorned condition). 6 Classification and Distribution of Living Primates Anthropology Fig II: Difference in the structure of strepsirhine and haplorhine primate nose (Source: Swindler, 2004). Traditionally, taxonomic classification relied upon physical similarities between species and lineages but with the advent of genetic technologies (such as the DNA-sequencing techniques), surplus genetic evidence have emerged over the past few years that provide direct between-species comparisons of DNA sequences (Jurmain et al., 2012). Goodman and his colleagues emphasized that humans and chimpanzees have only a 1.6% difference in the non-coding portions of their globin gene clusters, whereas there is a 2.1 percent difference between chimpanzees and gorillas (Gibbons, 1990) and when the entire genome is considered, reported differences between chimpanzees and humans range from 2.7 percent (Cheng et al., 2005) to 6.4 percent (Demuth et al., 2006). Genetic similarities in relation with fossil evidence highlighted that humans and chimpanzees last shared a common ancestor around 6–8 mya. Prosimians (Halbaffen or before-apes) are referred to as the lower primates owing to their primitive morphology and behaviour. The suborder Prosimii included three infraorder namely, Lemuriformes (all lemurs), Lorisiformes (all Lorises and Galagos) and Tarsiformes (all Tarsiers). On the other hand, 7 Classification and Distribution of Living Primates Anthropology anthropoids (monkeys, apes and man) - ‘manlike’ primates- are termed the higher primates. The suborder Anthropoidea comprised of two infra-orders Platyrrhini (all New World Monkeys) and Catarrhini (all Old World Monkeys, apes and humans). Several traits differentiate anthropoids, as a group, from prosimians (and most other placental mammals). Jurmain et al. (2012) provided account of these traits: 1. Generally larger body size 2. Larger brain (in absolute terms and relative to body weight) 3. Reduced dependence on the sense of smell, as indicated by absence of a rhinarium 4. Increased reliance on vision, with forward-facing eyes at the front of the face 5. Greater degree of color vision 6. Back of eye socket formed by a bony plate 7. Blood supply to brain different from that of prosimians 8. Fusion of the two sides of the mandible at the midline to form one bone (in prosimians they are two bones joined by fibrous tissue) 9. Less specialized dentition, as seen