HUMAN EVOLUTIONA Look Into Our Past

“It has often and confidently been asserted, that man's origin can never be known: but ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science.”

- Charles Darwin

WHAT IS HOMININ?

A taxonomic group that includes humans and their sister taxa chimpanzees.

- fossils date back between 6-7 million years Genetic analysis shows that

humans diverged from chimpanzees between 5-6 million years ago

WHERE DID IT ALL START?

Two debated theories: 1. Multiregional

Hypothesis Locally adapted

populations interbreeding

2. “Out of Africa” Hypothesis

Single population leaves and replaces existing populations over time.

Darwin predicted this when he wrote “The Descent of Man”

STARTING POINT

MITOCHONDRIAL EVE

• All mitochondria in human population are descended from the mitochondria of a single woman called “Mitochondrial Eve” about 200,000 years ago

• Mitochondrial DNA (mtDNA) only transferred via eggs (maternal)

EARLY HOMININS

Sahelanthropus Dates 6-7 mya Western Africa Small brain and most

primitive hominin fossil Was bipedal

EARLY HOMININS

Kenyanthropus platyops 3.5 mya Represented by skull

fragments, jaws, teeth, and leg and arm bones

EARLY HOMININS

Australopithecus afarensis 3.5 mya Fossil remains are most

extensive found (named “Lucy”)

Bipedal (fossilize footprints) Primitive features: low face,

long canines, long arms, small brain (400 cc), and curved fingers (tree climbing)

Lucy Video - Biointeractive

EARLY HOMININS

Paranthropus “robust” australopithecines Three named species Large molars and premolars

for chewing plant material May have made stone tools

(2.6 mya) Went extinct and didn’t

contribute to human lineage

EARLY HOMININS

Homo halibis Missing link between

Australopithecus and Homo (1.9 - 1.5 mya)

Greater cranial capacity (610-800 cc)

Flatter face and shorter tooth row

Stone tools (Olduwan technology)

ARCHAIC HOMO SAPIENS Homo erectus

1.6 mya – 200,000 years ago Modern human skull features Larger cranial capacity (avg.

1000 cc) Spread out from Africa to Asia Associated with stone tools

(Acheulian culture), more diverse than the Olduwan tools of H. halibus

First to use fire (500,000 years ago)

ARCHAIC HOMO SAPIENS

Homo neanderthalensis Europe and SW Asia Dense bones and projecting

brow Larger brains than us (1500

cc) Mousterian culture (stone

tools, burial rituals, brain surgeries?)

NOT a direct ancestor, but we may have interbreed with them

ARCHAIC HOMO SAPIENS Modern Homo sapiens

170 – 160 Kya Modern cranial capacity (avg.

1400 cc) Indistinguishable from us Started in Africa and

overlapped range with Neanderthals

Abrupt change 40,000 years ago allowed for “replacement” of Neanderthals

Crossed land bridge 12,000 years ago to Americas

EVOLUTIONARY DRIVING FORCES

Selective pressures put a premium on two traits throughout our evolution:

1. Bipedalism- A. afarensis fossil footprints (3.6 mya in

Tanzania)- great toe not splayed out

2. Cranial Capacity and Intelligence (high

selection!)- learning and

communication