Fossil Context and Geologic Time and Primate Evolution

Amino Acid Racemization

A dating method that measures the rate at which amino acids in fossils convert from one form to another over time, useful for dating organic materials up to several hundred thousand years old.

Anthropocene

The proposed current geological epoch, marked by significant human impact on Earth's ecosystems, climate, and geology.

Biostratigraphy

A relative dating method that uses fossilized animal remains to determine the age of rock layers.

Chronometric Dating

Also called absolute dating, this refers to methods that provide an actual age estimate for fossils or artifacts.

Dendrochronology

Tree-ring dating that counts growth rings in trees to establish an exact year-by-year timeline, useful for dating events up to 10,000 years ago.

Geologic Time Scale

A system that organizes Earth's history into different eons, eras, periods, and epochs, based on major geological and biological events.

Eon

The largest unit of geologic time, divided into four eons: Hadean, Archean, Proterozoic, and Phanerozoic.

Epochs

A subdivision of geologic time smaller than a period.

Eras

Large divisions of geologic time, each lasting tens to hundreds of millions of years.

Fossilization

The process of turning biological material into a fossil, often through mineralization, where organic material is replaced by minerals over time.

Holocene

The current epoch, beginning about 11,700 years ago, marked by human civilization and environmental changes due to human activity.

Hominin

Any species more closely related to humans than chimpanzees, including modern humans and our extinct relatives.

Isotopes

Atoms of the same element with different numbers of neutrons, some of which are radioactive and decay at a constant rate.

Law of Superposition

A principle stating that in undisturbed rock layers, the oldest layers are at the bottom and the youngest layers are at the top.

Paleomagnetic/Geomagnetic Reversal

A phenomenon where Earth's magnetic field reverses, leaving a record in rocks that helps date geological layers.

Radioactive Decay

The process by which an unstable isotope breaks down into a stable form, releasing radiation at a constant rate.

Radiocarbon Dating

A chronometric dating method that measures the decay of carbon-14 in organic material to determine its age, effective up to 50,000 years ago.

Relative Dating

A dating method that determines the age of an object relative to other objects, rather than providing a specific age.

Stratigraphy

The study of rock layers (strata) and their sequence in the Earth's crust, used to determine relative ages of fossils and artifacts.

Taphonomy

The study of what happens to an organism after death and how it becomes fossilized, including decomposition, burial, and preservation.

Trace Fossils

Fossilized evidence of an organism’s activity, such as footprints or burrows.

Adapoids

A group of early primates from the Eocene epoch considered ancestors of modern strepsirrhines.

Anthropoids

A higher primate group that includes monkeys, apes, and humans, characterized by larger brains and forward-facing eyes.

Apidium

A small, arboreal primate from the Oligocene epoch representing an early ancestor of New World and Old World monkeys.

Petrosal Bulla

A small bony structure at the base of the skull that encases the middle ear, a unique feature of primates.

Bilophodont

A type of molar tooth pattern found in Old World monkeys, with two ridges that run parallel.

Dental Apes

Early Miocene apes that had ape-like teeth but monkey-like bodies, representing an evolutionary transition.

Omomyoids

A group of early primates from the Eocene epoch, considered possible ancestors of haplorhines.

Plesiadapiforms

An early group of primate-like mammals from the Paleocene epoch with some primate traits but lacking key features.

Proconsul

An early Miocene ape that had an ape-like skull and dentition but a monkey-like body.

Y-5 Molar

A molar pattern in apes and humans characterized by five cusps forming a Y-shaped groove.

Arboreal Hypothesis

The idea that primates evolved traits for living in trees.

Visual Predation Hypothesis

The idea that primates evolved their traits to hunt small insects in trees.

Angiosperm Radiation Hypothesis

The idea that primates evolved to exploit new fruit resources from flowering plants.

Tarsier Hypothesis

The idea that anthropoids evolved directly from tarsier-like primates.

Omomyoid Hypothesis

The idea that anthropoids evolved from omomyoids, which share many features with modern haplorhines.

Adapoid Hypothesis

The idea that anthropoids evolved from adapoid-like primates.

Placement of Plesiadapiforms

Debate arises from their combination of primate-like traits and their lack of key features that define true primates.