Hominidae

hylobatidae

lesser apes

gibbons

live in tropical asia

low sexual dimorphism

highly arboreal

very long arms and experts at brachiation locomotion

omnivorous diet, but >50% fruit

Pan

Genus of chimpanzees and bonobos

2 species in sub-Sahara rainforests

arboreal and ground-dwelling

quadruped knuckle-walking

omnivorous

(Equally) closest relatives to humans

Gorilla

Genus of gorillas

2 species in sub-Sahara African rainforests

live in groups called troops

arboreal and ground-dwelling

strong sexual dimorphism

quadruped knuckle-walking

omnivorous, high percentage of foliage

Pongo

Genus of orangutans

2 species in southeast Asia rainforests

most arboreal and solitary of great apes

Sexually dimorphic

Quadruped fist walking

omnivorous, preference for fruit

Homo sapiens

modern humans

brachiation locomotion

using arms to swing from tree to tree, common among hylobatidae

sagittal crest

bone ridges in the skull, provides surface area for jaw muscle attack, common among male gorillas

grasping hallux

the adaptation of the big toe for easier locomotion in trees

Broca’s area

part of the brain that controls the ability to produce language; becomes prominent in the Homo genus

Benefits of evolution of BIG BRAIN (x4)

1. Store information
2. quickly process information
3. problem solving
4. abstract ideas

Costs of evolution of BIG BRAIN (x2)

1. lots of energy (brain is only 2% of body mass but uses 20% of energy)
2. more difficult childbirth (we have narrow hips but large heads!)

hypoxia

deficiency of oxygen; leads to fatigue, dizziness, headaches, insomnia, nausea, vomiting, and dilated veins

phenotypic plasticity

same genotype can produce different phenotypes; not evolution

EPAS1 gene

gene linked to red blood cell production

LCT

lactase gene

MCH

major histocompatibility complex (immune system)

Human niche construction

the process by which organisms construct important components of their local environment in ways that introduce novel selection pressures

ex) lactase persistence in humans

UVB

damages skin surface, causes sunburns and some skin cancers, but also causes the synthesis of vitamin D

UVA

breaks down folate

Genus Ardipithecus

lived \~4-5 mya

Fossils from Ethiopia

Grasping hallux

Hands similar to modern humans and pelvis suited for walking upright

Brain slightly smaller than modern chimps

Reduced canines

Genus Australopithecus

lived \~4-2 mya

Fossils in eastern Africa

Thought to be mostly related to genus *Homo*

Brain sizes \~35% the size of modern humans

High degree of sexual dimorphism

Mainly fruit diet but also evidence for meat consumption

*Australopithecus afarensis*

Oldest member of genus; lived 3-4 mya

“Lucy”

Strong evidence of bipedalism

Loss of grasping hallux

Curvature of fingers/toes adapted for grasping

Genus Paranthropus

lived 1.5-2 mya

“Robust” body type

Have sagittal crest

Genus Homo

2\.5-3 mya

Long lower legs

Smaller teeth

Larger brains

Bulge of Broca’s area

Evidence of tool, fire use, and burial of dead

Chimpanzee

Larger

male-dominated

more aggressive

Bonobos

smaller

female dominated

less aggressive

frequent sexual behavior helps resolve conflicts

greater preference for fruit