Theme 6 Flashcards
What are the 3 periods that characterize the early study of primate evolution?
Linneus’ Systema Naturae, discovery of 1st primate fossils in Europe, Darwin’s Origin of Species
Dating Methods
Provenance, original context, relative vs absolute (or chronometric), nature of material, geological context.
What is the crown group and stem group in primate classification?
Crown-everything present now.
Stem-Everything that occured before common ancestor.
Classification: Dietary Reconstruction
Body mass estimates, dental microwear, dental texture, molar tooth shape, molar cusp shape, enamel thickness.
Classification: social behaviours
Based on observations of extant (currently living) primates: Sexual dimorphism
Palaeocene Epoch
First primates, 66 million years ago. North America and Europe were subtropical.
Plesiadapiformes
North America, Europe, Asia. 53 genera, 140 species. Dental numbers: 3143. Procumbent central incisors, long snout, lateral orbits, claws, no postorbital bar. Included purgatorius, plesiadapis, and carpolestes.
Eocene Epoch
North America connected to Europe. Omomyidae (tarsiers), and Adapidae (lemurs)-first higher primates, first anthropoids.
Oligocene Epoch
Global temperature decline, reduction in forests. Fayum Desert, Egypt (17+ genera, warm tropical environment). Included Oligopithecidae, Parapithecidae, Propiliopithecidea, and Aegyptopithecus (first fossil similar to hominids).
New World Monkeys
Africa and South America Separate. Originated in Afrca, Lower sea levels and floating vegetation islands.
Miocene Epoch
20-5 million years ago. Origin of old world monkeys rare during early miocene (23-16 million years ago). Egypt, Libya, Kenya. Bilophodont molar. Included Victoriapithecidae, and Mesopithecus. Age of hominids, geological, climatic, and environmental changes. Land bridge between Asia and Africa. Increased temps, more tropical forests.
Early Miocene Epoch
23-16 million years ago, African Forests, woodlands. Proconsul: Y-S pattern, cingulum, no tail. (Afropithecus, Heliopithecus).
Mid Miocene
16-12 million years ago, cooler climate, reduced sea levels, land bridge between Africa and Eurasia
Late Miocene
12-5.3 million years ago. Cold, dry climates, increased open grasslands. Knuckle walking primates. Possible ancestors of chimps, gorillas, and orangutans. Sivapithecus and Gigantopithecus.
Molecular Systematics
Molecular data used to reconstruct phylogeny. Assumes that species who share molecular similarities are likely to share a common ancestor.
What did Sarich and Wilson find out?
Compared serum proteins in humans and great apes, found that African great apes and humans shared a common ancestor 5 million years ago.
Hominin Traits
Bipedalism, small generalized teeth, large brains, hairless.
Mosaic Evolution
Traits did not develop at the same time
Foramen Magnum in panins and hominins
Located more anteriorly in hominins, skull is in line with body.
Pelvis shape in panins and hominins
Hominins have a short, broad pelvis for walking upright. (bowl shaped).
Spine in panins and hominins
Hominins have an S shaped spine compared to the C shaped one in panins.
Valgus knee in panins and hominins
Hominins thigh bones are angled inwards for upright walking.
Feet in panins and hominins
Panins have opposable big toe for climbing. Hominins have a bipedal foot for walking, with transverse and longitudinal arches.
Human Gait
Has a stance phase and a swing phase
Why don’t we just fall over?
Large blade-like ilium shorter, ilium directed to side and not back, gluteal muscles used for propulsion, stability and balance.
Why did we become bipedal?
Most likely due to accessing food. Other theories include hunting, surveillance, thermoregulation, endurance running, walking in water etc.
Costs of Bipedalism: Gravity and Circulation
Greater risk of heart attack and stroke.
Costs of Bipedalism: Musculoskeletal Problems
“Fallen Arches,” prolapse of intervertebral disks, patello-femoral syndrome.
Costs of Bipedalism: Childbirth
Obstetric dilemma-narrow birth canal+large brain= incredibly difficult birth and labour.
Adaptations to the childbirth dilemma
Early birth, skull plates are unfused, flexible pelvis, obligate midwifery, wedge shaped lumbar vertebrae.
Facultative vs Obligate Bipedalism
Facultative- can be bipedal under extreme cirumstances
Obligate-Bipedal like us
Terrestrial vs Arboreal Bipedalism
Terrestrial-Protograde knuckle-walking, chimps and LCA.
Arboreal-Orthograde clamber, orangutans, using hands and feet
Human Brains
Larger, structure reorganized, encephalization, expensive tissue hypothesis, burns approximately 4.2KJ/min, significant dietary change-high quality diets+short digestive tracts makes for greater brain size.
Isometric vs Allometric Scaling
Isometric-body parts increase in size at the same pace
Allometric-body parts increase in size at different paces.
