Early Human Evolution and Australopithecine Divergence

Vocabulary flashcards covering key terms and concepts related to early human evolution, australopithecine characteristics, climate shifts, and dietary adaptations from lecture notes.

Human Fossil Record

Stretches nearly 7 million years, with most informative fossils starting around 5 million years ago.

First Key Adaptations (Early Human Evolution)

Bipedalism and Savanna Diets.

Ancestry (Human-Chimpanzee)

Humans and Chimpanzees diverged approximately 7-8 million years ago.

Ardipithecus ramidus

An early hominin (~4.4 mya) showing both bipedal and arboreal adaptations, including standing in trees to gather food and grasping with an opposable toe.

Mio-Pliocene Climate Shift

A global cooling trend beginning around 12 million years ago, leading to glacial periods, increased aridity, and expanding grasslands with shrinking tropics.

Mio-Pliocene Environmental Shift Effects

Gradual climate change that made forest margins patchy and intersected by grasslands, influencing bipedalism and leading to a migration out of forests to terrestrial life.

Bipedalism (Initial Adaptation)

Possibly first adapted to arboreal conditions, allowing for standing in trees and reaching with free hands.

Hominin Identification (Savanna Diet)

Indicated by changes in dentition, including expansion of post-canine dentition (molars and pre-molars), reduction of incisors, and thickening of enamel.

Australopithecus afarensis (Au. afarensis)

A species (3.9-2.9 mya) characterized as a complete biped with some minor arboreal tendencies like long arms and elongated fingers relative to the thumb.

Au. afarensis (Savanna Adaptations)

Showed increased size in post-canine dentition, post-orbital constriction, larger chewing muscles (Temporalis and Masseter), large zygomatics, and a cranial capacity similar to chimpanzees (~450 cc).

Australopithecine Divergence

A split in the Australopithecus line emphasizing diet, leading to 'robust' and 'gracile' forms.

Robust Australopithecines (Diet)

Adapted to a hardy diet of grasses, tubers, roots, and seeds, which were hard to chew and digest but abundant to collect.

Gracile Australopithecines (Diet)

Showed omnivory, including new, easy-to-process, high-energy foods.

Robust Australopithecine (Features)

Characterized by broad cheekbones (zygomatics), large backward extending zygomatic arch, postorbital constriction, sagittal crest, small incisors and canines, and very large molars.

Australopithecus aethiopicus

A robust australopithecine from Ethiopia (~2.5 mya) known for its heavy-duty chewing apparatus, including a sagittal crest, wide zygomatics, and post-canine megadontia.

Sagittal Crest

A bony ridge on the top of the skull, indicating large chewing muscles, seen in robust australopithecines like A. aethiopicus.

Post-Canine Megadontia

Refers to huge molars and premolars, a characteristic of robust australopithecines adapted to a tough diet.

Australopithecus boisei

A robust australopithecine from Tanzania (~2.2 mya), described as a larger version of Au. aethiopicus.

Australopithecus robustus

A robust australopithecine found in South Africa (~2-1.2 mya).

Gracile Australopithecus (Compared to Au. afarensis)

Featured a smaller build, slightly smaller cheek teeth, and a larger cranial capacity (~430-520 cc), indicating increased encephalization.

Increased Encephalization

Brain growth facilitated by nutrient intake from new food sources, observed in Gracile Australopithecus.

Meat Eating and Encephalization

Meat provided higher energy yield, was easier to digest, led to a reduction in the intestinal tract (saving energy), and enabled a more nutritious diet, all contributing to brain growth.

Sophisticated Tool Kit and Cooperation

Demanded by a more nutritious diet paired with reduced energy requirements, suggesting more complex behaviors.