Overview
This lecture covers how primates, including humans, are classified, explores key traits of different primate groups, and details evolutionary trends, taxonomy, great ape characteristics, and social structures.
Systematics and Classification Methods
- Scientists classify organisms using classic taxonomy (based on Linnaean ranks) and cladistics (based on shared evolutionary traits).
- Classic taxonomy names species using binomial nomenclature (genus and species).
- Cladistics groups organisms by unique derived traits, forming grades for related species.
- Both systems are used together for more accurate classification.
Cladistics Key Concepts
- Plesiomorphy: primitive trait found in ancestral and descendant species (e.g., five digits in primates).
- Apomorphy: new derived trait found only in descendant species (e.g., nails in primates).
- Autapomorphy: unique derived trait in a specific group (e.g., lack of tail in apes).
- Synapomorphy: shared derived trait inherited from a common ancestor (e.g., bipedalism in Hominini).
- Homoplasy: similar traits evolved independently in different groups (e.g., brachiation).
Primate Classification and Evolutionary Trends
- Primates (order Primates) are mammals, closely related to tree shrews and colugos.
- Key evolutionary trends: unspecialized skeleton, large brain, reduced reliance on smell, increased reliance on vision, prehensile hands/feet, opposable thumbs/toes, nails, long life stages, learned behavior, diurnality.
- Primates split into strepsirrhines (lemurs, bushbabies) with primitive traits and haplorhines (tarsiers, monkeys, apes) with derived traits.
- Old World and New World monkeys are distinguished by nostril shape and other features.
Modern Primate Taxonomy
- Strepsirrhines: retain moist, complex noses and larger olfactory bulbs.
- Haplorhines: simpler, dry noses, less reliance on smell.
- Old World monkeys: divided into cheek-pouched cercopithecines and leaf-eating colobines.
- Apes: lesser apes (gibbons, siamangs) and great apes (including humans) in Hominidae family.
Great Ape Characteristics
- Features: large brains, Y-5 molar pattern, honing complex (large canines), upright trunk, mobile shoulders, long arms, sexual dimorphism, long life stages, nest building, tool use, symbol learning.
- Human evolution features: longer legs, straighter hand/foot bones, increased brain size, reduced canine dimorphism, reduced sexual dimorphism.
Social Organization in Great Apes
- Chimpanzees/bonobos: male philopatry, fission-fusion groups, polygynandry (multiple mating partners for both sexes).
- Orangutans: mostly solitary, polygynous, dominant males have multiple mates.
- Gorillas: one-male groups (except mountain gorillas), polygynous, male defense and mate-guarding.
Key Terms & Definitions
- Classic Taxonomy — classification based on hierarchical ranks and physical traits.
- Cladistics — classification based on shared evolutionary traits.
- Plesiomorphy — ancestral trait present in all descendants.
- Apomorphy — new, derived trait in a group.
- Autapomorphy — unique trait in a particular group.
- Synapomorphy — derived trait shared by groups from a common ancestor.
- Homoplasy — independently evolved similar trait in different groups.
- Strepsirrhine — primates with primitive characteristics (e.g., lemurs, bushbabies).
- Haplorhine — primates with more derived traits (e.g., tarsiers, monkeys, apes).
- Y-5 Molar — molar with five cusps in apes.
- Honing Complex — enlarged canines sharpened by contact with lower premolars.
- Polygynandry — mating system with multiple partners for each sex.
- Philopatry — tendency for a sex to remain in its natal group.
Action Items / Next Steps
- Review taxonomic charts of living primates.
- Study evolutionary trends and key characteristics of each primate group.
- Prepare examples of primate social structures for discussion.