Introduction to Evolutionary Anthropology Shawn M. Lehman Chapter 4 Living Primates

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1 Introduction to Evolutionary Anthropology Shawn M. Lehman Chapter 4 Living Primates Primate Taxonomy and Characteristics Primates belong to the order Mammalia Mammals are characterized by general morphology, thermoregulators, have hair/fur, four-chambered heart, spinal cord, neocortex region in the brain (sensory perception), spatial reasoning, conscious thoughts and are homeothermic (ability to use energy from food to produce heat and self-regulate internal temperature. Mammals are the only animals with sweat glands (used to cool the body down using the process of evaporation). Characters that set primates apart from other mammals Grasping hands and feet Opposable big toe or thumb Flat nail on at least one digit (allows precision grip) Reduced olfactory apparatus (smell) Large brain size Dermatoglyphics with ridges (fingerprints) Postorbital bar Petrosally formed auditory bulla Collarbone (extensive shoulder movements) Radius and Ulna (allows precise hand movements) Forward facing eyes and stereoscopic vision (overlapping field of vision) Due to their vision, primates have depth perception Long periods of infancy, childhood, and adulthood (long life span) Greater parental investment Socialize, reproduce with the members of the same species Primates are of interest to anthropologists because they can help us to study human evolution through the principal of homology. Because we share a common ancestor human and nonhuman primates are similar morphologically, physiologically, and even behaviorally. Primates are a diverse order. This diversity includes diet: some primates eat primarily leaves, while others rely on fruit, or insects, or even sap. Diversity in social organization: some primate taxa live in multimale groups, while others live in single male groups Diversity in activity patterns: some are active during the day (diurnal); others are active at night (nocturnal). Primates can be divided into two suborders: The strepsirhini (lemurs, lorises, and galagos) and the haplorhini (tarsiers, monkeys, apes, and humans) 1

2 Strepsirhini (Old world monkeys) Dental tooth comb (lower incisors can be used to groom) Moist rhinarium (wet nose (enhanced sense of smell)) Unfused mandibular and frontal symphases Tapetum lucidum (night vision) Postorbitol bar ring of bone around the eye socket Two superfamilies: lemuroidea and lorisoidea Lemuroidea Lorisidae Galagos Found on the island of Madagascar and Comoro range in body mass arboreal quadrupeds Vertical clinging and leaping is the primary form of locomotion Eat fruits, leaves, flowers, and insects Many are nocturnal Sleep together in tree holes during the day Larger lemurs are usually diurnal males leave group after sexual maturity Females are often more dominant than males Found throughout subsaharan Africa and Southeast Asia Lorises and galagos Range in body mass (100g 1.6kg) Arboreal quadrupeds Nocturnal & solitary foragers Varied diets (plants and insects) Slow lorises have toxins (allergen) Sub-Saharan Africa Usually weigh >500g Nocturnal arboreal Solitary foragers Feed on animal prey & fruit Rapid quadrupedal running & leaping 2

3 Haplorhini (new world and old world monkeys) Dry nose Retinal fovea (reduced night vision but better visual acuity) Postorbital closure Fused mandibular and fronal symphases (exception: tarsier) All have nails excepts for tarsier Single-chambered uterus One pair of nipples (exception tarsier) Three infraorders: tarsiiformes, platyrrhini, and catarrhini Tarsiiformes Platyrrhini Catarrhini One genus (tarsius) Southeast asia Small body size (80 130g) Relatively large eyes, with fused lower leg bones Entirely faunivorous (insects, snakes, lizards) Grooming claw on 2 nd and 3 rd finger Long legs compared to the rest of the body Rapid leaps Can turn their heads 180 Eyes are immobile Central and South America Dental formula Flat noses & side facing nostrils New world/neotropic monkeys (central and south America) Body mass 110g-11.4kg Eat fruits, flowers, leaves, and insects Arboreal Aotus only nocturnal exception Cebidae, atelidae (prehensile tail), & callitrichidae (tamarins, marmosets, and Goeldi, they usually have twins, brightly coloured, one breeding female with many males and males help rear the infants) Africa, Asia, Southeast Asia Dental formula Body mass 1kg-175kg Cercopithecidae, hylobatidae, and hominidae Cercopithecidae and hylobatidae have ischial callosities (sitting pads) Variety of diets, social organizations, and adaptations Bunodont molars Hylpbatidae and hominidae lack tails and have larger brains and bigger body size 3

4 Subgroups of catarrhini Cercopithecinae Africa Range in body mass (1kg-32kg) Sexually dimorphic (males larger than females) Eat ripe fruit which is stored in their cheek pouches Arboreal quadrupeds Variety of social groups (monogamous, multi-male, multifemale) Cercopithecidae (Catarrhini) Long narrow nose & lose trunk Have tails Bilophodont teeth Colobinae Africa and Asia High cusps on their molar teeth Long tails and hindlimbs Short thumbs No cheek pouches Range body mass ( kg) Most are arboreal quadrupeds Eat leaves multi-chambered stomach Live in social troops (5-90 individuals) Hylobatids (catarrhini) Small bodied ( kg) Southeast asia Longer forearms relative to body size Brachiation (ability to swing from branch to branch) Gibbons: eat ripe fruit, leaves and invertebrates Hominidae (catarrhini) broad nose & short wide trunk no tails Y-5 molar Large bodied apes (orangutans, gorillas, chimpanzees & humans) Orangutans only large bodies apes of asia Chimpanzees and gorillas equatorial areas of Sub Saharan Africa Body mass ranges from 42kg (chimps) 175kg (gorillas) Long arms, hands and feet Sexually dimorphic Quadrumanous climbing helps move through arboreal habitat Gorillas and chimps - knuckle-walking Gorillas folivorous in eastern Africa and eat fruit in western Africa Orangutans and Chimps fruits (frugivorous diet) Chimps hunt and eat 35 types of vertebrate animals Have the ability to made and use tools (termites, nuts) Orangutans lead solitary lives Gorillas (9-12 individuals) and chimps (50) are highly social Important research was carried out by Jane Goodall Gombe stream in Tanzania 4

5 Body Size The reason for the scaling difference on primates is that area and volume change at different rates as the linear dimensions of the animal increases Area increases by a function of a square ( 2 ) Volume increase by a function of a cube ( 3 ) If an animal doubles in size than the area x4 (2x2) and the volume x8 (2x2x2) Small animals lose more energy (heat loss) than large animals Effects of Body Size on Primate Life Size-related scaling applies to almost every ecological aspect of an organism Diet Small primates require more energy per unit of weight than a large-bodied primate Large primates can eat large amounts of low-quality foods such as leaves Small primates must eat small amounts of high quality foods such as insects Locomotion Small primates tend to leap more than large bodied primates Limitations imposed by branch size on an arboreal lifestyle Life history Larger animals tend to live longer than small animals (not to scale) Human are smaller than gorillas but humans have a greater life expectancy than gorilla Ecology and Behaviour Primate Habitats Most primates live in forest habitats such as the tropical rainforest The tropical rainforest gets about 3m of rainfall per year, is hot and humid, contains lots of life (2/3 of species are located there), Africa, Asia and Southeast Asia Some primates live in deserts to mountainous pine forests. Primate species occupy a specific ecological niche Primates in tropical Ecosystems Evolutionary ecology of primates is a result of complex bottom-up and top-down processes Bottom-up processes: Interactions between organisms involving physical or chemical factors such as temperature or nutrient availability Top-down processes: influence of consumers, such as predator, on prey Primates are dependent on plants and if there are changes that alter the plants there will be cascading effects on primates Ranging Patterns Movement is restricted to known areas Daily path length refers to the one-dimensional distance travelled by a primate during its daily active period Day range 2-D area used by a primate throughout months or years Core area most frequently used part of the home range 5

6 Territory an area actively defended by an individual or a group The distribution and abundance of food resources, the size and shape of the habitat, altitude, and the type of abundant predators can influence primate-ranging patterns In some groups when males reach maturity they leave their group. Sociality Before observing primate behaviour one must ensure that the primates are habituated this means the primates must become used to the presence of the human Primates have complex social lives Some primate social behaviours include: deception, female mate choice, homosexuality, kin recognition, spite, welfare, friendship, and sex for pleasure Social grooming Primates do not only groom one another when they are dirty They groom to establish and maintain alliances, reconcile conflict, and exchange for other resources such as food and sex. Dominance Hierarchies A social order sustained by aggression, affiliation, or other behaviour patterns Classifying primate social organization There are four classification schemes 1. Residence group composition sorting the group by age and sex 2. Mating systems mating patterns exhibited by individuals 3. Foraging coherence which individuals forage together in time and space 4. Female and male philopatry which animals stay and which animals leave a social group. Female philopatry is when the females stay in the birth place while the males emigrate (more common) Male philopatry is when the males stay in their birthplace while the females emigrate. Why do Primates Live in Groups? There are three main theories 1. Living in large groups may provide protection from predators. More eyes and ears mean better detection of predators. In some primates rather than fleeing due the presence of a predator they alert the group and mob the predator. 2. May have improved access to food. Resource defense active defense of a food resource by an individual or group. 3. Increased access to potential mates. Due to the high cost of infant rearing and production in females they must rely on the group to support her needs. Some group members also aide with infant rearing 6

7 There are also disadvantages in living within a group - Larger groups attract the attention of predators - Larger groups suffer from more intragroup competition for food than smaller groups - Smaller group size occurs because the cost of within-group competition outweigh the benefits of improved predator detection - There is a devastating effect of infectious diseases on group-living primates Conservation Primates are increasingly threatened by human activities such as habitat disturbance and hunting pressures. Effects of agriculture on primates agriculture have deleterious effects on primates by altering tropical forests. Humans slash and burn to clear the forest for agriculture. The ashes provide fertilization for the soil, which tend to be nutrient poor. Increase population of humans has increased the pressure on resident primates. Effects on Forest Fragmentation on Primates Larger forest fragments contain more primate species while smaller forest fragments causes the species to disappear due to increased predation. Effect of Hunting on Primates Hunting pressures on primates vary throughout the tropics. Some locals don t hunt primates due to cultural beliefs. Larger species have slower reproduction rates than small species, resulting in poorer population recovery Hunting primates in Africa is economical (bushmeat trade). Conservation Status of Primates International Union for the Conservation of Nature and Natural Resources (IUCN) Red list of threatened species lists the global conservation status of plants and animals. 37 primate taxa a considered critically endangered and 57 are listed as endangered. 7