Key Features and Evolution of Primates

Features of Primates

Flat nails, opposable big toe, large brain, eyes on front of face, color vision, post-orbital bar, sociality, unique ear region, generalized skeleton, grasping hands and feet, retention of clavicle.

Promisians

Un-enclosed eye orbits, longer snout, split upper lip, smaller brain, lower jaw in two pieces.

Anthropoids

Enclosed eye orbits, larger brain, lower jaw is one bone, orbits with more forward orientation, molars with flatter cusps.

New World Monkeys vs Old World Monkeys

New World Monkeys have a dental formula of 2-1-3-3, while Old World Monkeys have 2-1-2-3; New World Monkeys have no bony ear tube, while Old World Monkeys have a bony ear tube.

Importance of Studying Primates

We can learn more about ourselves and human evolution, early hominin behavior, shared behavior patterns due to a shared ancestor, psychosocial behavior, cognition, brain disorders, empathy, and conservation efforts.

Reason for Evolution of Social Groups

To help ward off predators and enhance survival through group safety.

Advantages of Living in Social Groups

Grooming for health and disease prevention, better reproductive chances, protection of territories, and shared food resources.

Disadvantages of Living in Social Groups

Violent fights over mating and territory, competition for food, and rapid spread of sickness in large groups.

Prehensile Tail

A tail that can grip and grab onto things, found in New World Monkeys.

Natural Means of Preservation

Freezing, amber, mummification, trace fossils, coprolites.

Fossilization Process

Requires rapid burial before decay, followed by mineral replacement of organic material in bone.

Areas of Investigation in Fossils

Classification, locomotion, sex, mating system, diet, health/disease, age of death, time of death, paleoenvironment, and taphonomy.

Taphonomy

Study of processes that brought a fossil to its burial assemblage.

Epochs of the Cenozoic Era

Holocene, Pleistocene, Pliocene, Miocene, Oligocene, Eocene, Paleocene.

Relative vs Absolute Dating

Relative dating is based on superposition and stratigraphy; absolute dating is based on radioactive decay.

Half-Life

The decay rate of atoms, measuring the time it takes for half of the original amount of isotope to decay.

Proportion of Atoms Remaining

After 12,000 years with a half-life of 4,000 years, 1/8th of the original parent atoms will remain.

Examples of Relative Dating

Stratigraphy (principle of superposition), biostratigraphy (same fossil species), flourine content.

Examples of Absolute Dating

Dendrochronology (tree rings), radiometric dating (carbon-14, potassium-argon, uranium-238), thermoluminescence.

Climate Trend of Cenozoic Era

The climate was drying and cooling, leading to the age of mammals.

Order of Geological Time

Eon - Era - Period - Epoch.

Strata

Discrete layers of deposits.