Human Bio Chapter 5

Australopithecus Afarensis

First clear evidence of bipedalism, increased sexual dimorphism, “Lucy”

Homo Habilis

Created tools, larger brain, ate meat

Homo Erectus

Used fire and tools, migrated out of Africa, larger brain than Homo habilis, even more distinct sexual dimorphism, likely started pair bonding, shared responsibilities in childrearing

Homo Neanderthalensis

Genetically closest to Homo sapiens, interbred with Homo sapiens

Homo Sapiens

Modern humans, most advanced language, culture, and tools

Genetic Similarities Between Chimps and Humans

99.8% similar; single nucleotide substitutions = 1.2% different, duplications and insertions = 3-4% different)

Human-Chimp Divergence

4.5-6 million yrs

Human-Gorilla Divergence

6-8 million yrs

Human-Orangutan Divergence

12-16 million yrs

Evidence for Chr. 2 Fusion

-banding pattern matches 2 separate chimp chr.

-2 centromeres

-internal telomeres

FOXP1

Brain development and movement coordination

FOXP2

Speech/language development and motor control in humans

FOXP3

Regulates immune system

FOXP4

Neural and lung development

FOXP2 Importance to Human Evolution

Enabled speech, language learning, and cultural transmission

FOXP2 Difference Between Humans and Primates

2 nucleotide substitution

FOXP2 on Brain Regions

-Cortex (planning)

-Striatum (motor learning/sequencing)

-Cerebellum (coordination).

FOXP2 in Mice Ultrasonic Whistles

-Wild type: high amount of whistles

-Heterozygous: mild brain and vocal problems

-Homozygous: severe brain malformations and no vocalization

FOXP2 in Songbirds

Song learning and imitation

FOXP2 Location

Human chr. 7q31

Learning Feedback Loop: Preferred Outcome

Preferred phenome, song, temperature → comparator

Learning Feedback Loop: Comparator

Comparing expected vs. actual performance → error signal

Learning Feedback Loop: Motor System

Receives error signal → calculates physical response

Learning Feedback Loop: Behavior Produced

From motor system → physical response

Learning Feedback Loop: Outcome Perceived

Outcome of physical response → comparator

Contralateral Control

Brain's hemispheres control the opposite side of the body

Left Hemisphere

Contains Broca’s and Wernicke’s areas; typically dominant for language

Brain Regions for Hearing

Auditory cortex in temporal lobe (processes sound) and Wernicke’s area (comprehends words)

Brain Regions for Speaking

Broca’s area in frontal lobe (produces speech) and M1/primary motor cortex (mouth and tongue movement)

Aphasia

Inability to comprehend/formulate language

Broca’s Aphasia

x - fluency, repetition

o - comprehension

Wernicke’s Aphasia

x - comprehension, repetition

o - fluency

Conduction Aphasia

x - repetition

o - fluency, comprehension

Transcortial Motor Aphasia

x - fluency

o - comprehension, repetition

Transcortial Sensory Aphasia

x - comprehension

o - fluency, repetition

Transcortial Mixed Aphasia

x - fluency, comprehension

o - repetition

Global Aphasia

x - fluency, comprehension, repetition

Population-Level Chimp Handedness

Tools (RH), termite fishing (LH), nutcracking (RH), wadge dipping (slight RH)

Chimp Handedness Heritability

Strong mother → offspring; either genetic or learned

Evidence for Neanderthal Speech

Similar hyoid bone shape/position, FOXP2, longer oral cavity, shorter pharynx → similar vocal anatomy and breathing control

Evidence for Human-Neanderthal Interbreeding

Modern Eurasian genome is 1-4% Neanderthal, shared genes (like FOXP2) through gene flow

Shared FOXP2 in Humans and Neanderthals

Speech may predate humans/Neanderthals from common ancestor → interbreeding may have reinforced speech genes

Vocal Tract Reconstruction

Helps estimate Neanderthal speech ability

Sandra Martelli’s Study on Human vs. Neanderthal Speech Capability

Different mouth/nasal cavity shape → may not have full modern vowel and consonant capacity, but could probably comprehend

Speech vs. Choking Risk

Lowered larynx and flexible tongue make speech possible → pushes epiglottis to anatomical limit, increases choking risk

Infant/Chimp vs Adult Larynx Position

-Infant/chimp: high → breathe while swallow, limited vocal range

-Adult: low → longer pharynx, reshaped oral cavity for full vowel range