Unit 4 HBY - Hominin Classification

Study Notes

Human Classification and Taxonomy

Humans are classified in the same taxonomic family as great apes, differentiated by DNA sequences affecting traits such as cerebral cortex size, digit mobility, locomotion adaptations, prognathism, and dentition.
Primate Order is further classified, with a focus on understanding the family Hominidae, which includes humans and great apes.

Hominin Classification Line

Humans and apes belong to the superfamily Hominoidea, classified as Hominoids.
Modern humans and great apes comprise the family Hominidae, referred to as Hominids.
The subfamily Homininae includes all modern and extinct chimpanzees and humans.
The tribe Hominini encompasses all extinct ancestors and modern humans, classified as Hominins.

Evolution of Classification Terms

The term 'hominid' has evolved; it now includes all great apes and their ancestors, while 'hominin' refers specifically to modern humans and their extinct ancestors.
Confusion arises due to older texts using definitions that align 'hominid' with what 'hominin' signifies today.

Dentition in Hominids

Hominids are generally omnivorous, reflected in their generalized dentition.
There is a trend of decreasing tooth number in apes and humans compared to lesser primates, likely due to reduced jaw size and prognathism.
Both apes and humans possess 32 teeth with a dental formula of (2:1:2:3); lemurs and lorises have 36 teeth with a pattern of (2:1:3:3).
Monkeys and apes exhibit large canines, with a gap (diastema) facilitating mouth closure, while humans lack this gap.

Canine Size and Function

Male apes have larger canines for defense and intimidation compared to females, while humans have smaller, equally sized canines.

Molars and Dietary Adaptation

Apes and humans have 5-cusped molars; monkeys possess 4-cusped molars.
The evolution of molars is linked to a fruit-heavy diet in apes, necessitating larger grinding surfaces for fibrous plants.
Apes have thinner enamel on their teeth as an adaptation to their diet, while human teeth feature thick enamel.

Jaw Structure and Adaptation

Apes have larger mandibles, suitable for grinding fibrous plants, while humans have developed a chin for skull protection.
The size of the jaw in humans reflects a less robust dietary requirement than that of apes.

Dental Arcade Evolution

The shape of the dental arcade, or the arrangement of teeth in the upper jaw, evolves from the U-shaped in apes to the parabolic V-shape in humans.

Prognathism Characteristics

Prognathism refers to the decrease in snout size and increased facial flatness in humans, reducing reliance on olfaction.
A flatter face enhances stereoscopic vision, with forward-facing eyes and expanded visual processing areas in the brain at the expense of olfactory areas.

Description

Explore the fascinating world of hominin classification in this Unit 4 flashcard quiz. Learn about key concepts such as DNA differentiation, adaptations in bipedalism, and the significance of prognathism in human evolution. Perfect for reinforcing your understanding of primate taxonomy and its implications.