UNIT: 6HUMAN EVOLUTIONCAMPBELL & REECE, 2010CHAPTER 34 P.728-733EDUDINKNOTES

• Human evolution: refers to the evolutionary process leading up to the appearance of modern humans.

• The study of human evolution involves many scientific disciplines, including physical anthropology, primatology, archaeology, linguistics, embryology and genetics.

INTRODUCTION

• The species Homo sapiens is about 200,000 years old, which is very young, considering that life has existed on Earth for at least 3.5 billion years.

• Derived from early Homonins (Homonids)

INTRODUCTION

• Human evolution is characterized by a number of morphological, developmental, physiological, and behavioural changes .

• The most significant of these adaptations are

• 1. bipedalism (1.9 million years ago), • 2. increased brain size, • 3. lengthened ontogeny (gestation and infancy), • 4. decreased sexual dimorphism.

Characters that distinguish humans from other apes:

• Upright posture and bipedal locomotion• Larger brains• Language capabilities and symbolic

thought• The manufacture and use of complex

tools• Shortened jaw• Shorter digestive tract

The Earliest Hominins

• The study of human origins is known as palaeoanthropology

• Hominins (formerly called hominids) are more closely related to humans than to chimpanzees

• Paleoanthropologists have discovered fossils of about 20 species of extinct hominins

A timeline for some selected Hominin species

• Hominins originated in Africa about 6–7 million years ago.

• Early hominins had a small brain but probably walked upright.

• Two common misconceptions about early hominins:– Thinking of them as chimpanzees– Imagining human evolution as a ladder

leading directly to Homo sapiens• We are taking a closer look to the Hominins

called Australopiths and Homo

AUSTRALOPITHS• Australopiths are a paraphyletic assemblage of

hominins living between 4 and 2 million years ago.

• Some species walked fully erect. • “Robust” australopiths had sturdy skulls and

powerful jaws.• “Gracile” australopiths were more slender and

had lighter jaws .• Australopiths got their name from the 1924

discovery in South Africa of Australopithicus africanus (“southern ape of Africa”)

AUSTRALOPITHICUS AFRICANUS• Walked fully upright (Bipedal)• Had humanlike hands and teeth.• Had a brain 1/3 of present humans.

Mrs Ples” was an Australopithecus africanus that lived more than 2-million years ago in the Cradle of Humankind

AUSTRALOPITHICUS AFARENSIS• Australopithicus afarensis skeleton was discovered

in Afar (Ethiopia) in 1974.• It was 40% complete, 1m tall and named Lucy.• In 1990 more A. afarensis fossils were discovered.• It showed that they existed as a species for at least

1 million years.• Brain size of chimpanzee.• Longer lower jaw.• Arms longer than humans – arboreal movement

EVIDENCE OF TOOL USE• The oldest evidence of tool use, cut marks on

animal bones, is 2.5 million years old• These bones found in Ethiopia.• The marks on bones suggested that Hominins cut

flesh from animals using stone tools.• Stone tool use originated before the development

of large brains.

HOMININS: HOMO• The earliest fossils placed in our genus Homo are

those of Homo habilis, ranging in age from about 2.4 to 1.6 million years

• Stone tools have been found with H. habilis, giving this species its name, which means “handy man”

• Homo ergaster was the first fully bipedal, large-brained hominid

• The species existed between 1.9 and 1.5 million years ago

• Homo ergaster shows a significant decrease in sexual dimorphism (a size difference between sexes) compared with its ancestors.

• Homo ergaster fossils were previously assigned to Homo erectus; most paleoanthropologists now recognize these as separate species.

• Homo erectus originated in Africa by 1.8 million years ago

• It was the first hominin to leave Africa

Homo egaster

COMPARISON BETWEEN HOMO ERECTUS AND MODERN MAN

Homo neanderthalensis• Neanderthals, Homo neanderthalensis, lived in

Europe and the Near East from 200,000 to 28,000 years ago.

• They were thick-boned with a larger brain, they buried their dead, and they made hunting tools.

HOMO SAPIENS• Homo sapiens appeared in Africa by 195,000

years ago.• All living humans are descended from these

African ancestors.• The oldest fossils of Homo sapiens outside Africa

date back about 115,000 years and are from the Middle East.

• In 2004, 18,000 year old fossils were found in Indonesia, and a new small hominin was named: Homo floresiensis

Homo floresiensis

• Rapid expansion of our species may have been preceded by changes to the brain that made cognitive innovations possible.

• For example, the FOXP2 gene is essential for human language, and underwent intense natural selection during the last 200,000 years

• Homo sapiens were the first group to show evidence of symbolic and sophisticated thought.

Art, a human hallmark

SUMMERY OF OUR “ANCESTORS”

SUMMERY OF OUR “ANCESTORS”1. HOMO HABILIS ~ NICKNAME: Handyman LIVED: 2.4 to 1.6 million years ago

HABITAT: Tropical Africa DIET: Omnivorous – nuts, seeds, tubers, fruits, some meat

2. HOMO SAPIEN ~ NICKNAME: Human LIVED: 200,000 years ago to present HABITAT: All DIET: Omnivorous - meat, vegetables, tubers, nuts, pizza, sushi

3. HOMO FLORESIENSIS ~ NICKNAME: Hobbit LIVED: 95,000 to 13,000 years ago HABITAT: Flores, Indonesia (tropical) DIET: Omnivorous - meat included pygmy stegodon, giant rat

4. HOMO ERECTUS ~ NICKNAME: Erectus LIVED: 1.8 million years to 100,000 years ago HABITAT: Tropical to temperate - Africa, Asia, Europe DIET: Omnivorous - meat, tubers, fruits, nuts

5. PARANTHROPUS BOISEI ~ NICKNAME: Nutcracker man LIVED: 2.3 to 1.4 million years ago HABITAT: Tropical Africa DIET: Omnivorous - nuts, seeds, leaves, tubers, fruits, maybe some meat

6. HOMO HEIDELBERGENSIS ~ NICKNAME: Goliath LIVED: 700,000 to 300,000 years ago HABITAT: Temperate and tropical, Africa and Europe DIET: Omnivorous - meat, vegetables, tubers, nuts

7. HOMO NEANDERTHALENSIS ~ NICKNAME: Neanderthal LIVED: 250,000 to 30,000 years ago HABITAT: Europe and Western Asia DIET: Relied heavily on meat, such as bison, deer and musk ox

COMPARISON OF 3 HOMO SPESIES

HUMAN EVOLUTIONARY TREE

MAP OF EARLY HUMAN MIGRATION

1. Homo sapiens2. Neanderthals3. Early Hominids