Chapter 1:

Out of the Woods

Theory of Evolution

Charles Darwin19th century British scientistVoyage of the Beagle: 1831-1836 “On the Origin of Species by means of

natural selection”: 1859

Charles Darwin

H.M.S. Beagle

On the Origin of Species 1859

The Reaction to Darwin 1860

Darwin’s Argument for the Evolution of Species Observation # 1 Most species produce far more offspring than

could possible survive Example: One pair of mice could produce

about 40 babies a year and these babies could have their own offspring after only six weeks

Imagine what would happen if this process kept going indefinitely

Darwin’s Argument for the Evolution of Species Observation # 2 An individual’s chances of survival will be

affected by the environment in which it lives Example: The environment includes the

weather, finding food and a mate,finding somewhere to live and other animals and plants

Darwin’s Argument for the Evolution of Species Observation # 3 Individuals vary. Some will be better adapted

to their environment and will stand a better chance of surviving.

Darwin did not know what caused variation—we now know it is caused by mutations and the mixing up of genes during sexual reproduction.

Darwin’s Argument for the Evolution of Species Conclusion # 4 If the better-adapted individuals survive long

enough to reproduce … and if they pass the characteristics [genes] that helped them to survive on to their offspring. . . Their offspring will also stand a better chance of surviving.

This idea is sometimes called “the survival of the fittest”

What is a species? Is it just animals and plants that are “similar”?

How similar do they have to be? Who decides? How?

Are these animals from the same species?

Here is their offspring

So why aren’t horses and donkeys part of the same species?

Because mules are not fertile!

How did the giraffe get such a long neck?

Lamark’s Answer: they stretched their necks to reach food: inheritance of acquired characteristics

Darwin’s Answer: giraffes with mutation for longer necks were able to reach food—>survived in greater numbers—>lived to reproduce and pass along their long-necked gene

Did Humans Evolve?

Traditional religious answers spotlight human’s place at center or peak of creation

Modern scientific accounts focus on the emergence of all life forms as equally important: inter-relatedness of all life

Link

What is the subject and the source for the picture on p. 8-9?

Australopithecus scientific and artistic re-imagination and

reconstruction of 5 million years ago based on scientifically informed guess work

A real picture?

What are the Laetoli footprints?

made by ancient human ancestors 3.5 million years ago

several hominids walking in a group made footprints in soft volcanic ash that were covered up, buried, preserved, and came to light

Link

Laetoli Footprints

Laetoli Footprints 2

Laetoli Footprints 3

Where were the footprints found?

the lakebed of an ancient lake in northern Tanzania (East Africa)

What do they show us about our earliest ancestors?

he/she was a two-legged mammal with upright posture—>"bi-pedal”

Link

Bi-pedalism

Bi-pedalism 2

Who directed the team that found them? When? Where?

Mary Leakey—>wife to husband Louis Leakey: British archaeologists

1976—> after more than 40 years of looking! Tanzania

Why are teeth so commonly found among fossils? Why are they so important to archaeologists?

teeth are the hardest material in human body—> enamel

slowest to decompose—>lasts much longer than the rest of the body

chewing marks on teeth indicate diet—>infer ecological niche, lifestyle, intelligence

By the way, what is a fossil?

a mineral replica of a skeletal piece of an animal

Why are early human fossils rarer and more precious than diamonds?

original population of early hominids was tiny compared to human population today

after death, corpses here usually displaced and devoured by larger predators and scavengers

if skeleton intact, it is usually decomposed ("eaten") by microorganisms—>"circle of life and death"

if intact, it must be rapidly covered by protective sediment

if protected, it must be fossilized by mineral replacement of organic material

if fossilized, it must come to light and be discovered by someone who knows what it is!

How are fossils made?

Link

What is the name of the species that made the Laetoli footprints?

Australopithecus afaransis—> "Southern ape of the afari people"

Australopithecus afaransis

Australopithecus afaransis

When were the fossils originally made? How?

3-4 million years ago footprints made in soft volcanic ash and

immediately covered Link

What are three anatomical differences between apes and humans that make it possible for humans to walk upright?

extended knee and hip joint allow straight leg walking, not ape waddling

center of gravity centralized under skull, not thrust forward as in apes

curved lower spine to support skull, not attached as in apes

parallel big toe, not opposable grasping toe, in order to distribute weight while walking

Link

The First Couple?

Why is the artist's picture on p. 16 controversial?

sentimental pairing of male and female "couple"

more likely pair: mother and child

What is a hominid?

member of human "family" of ancestors walked upright

Why was bi-pedalism such a significant change in human history?

frees forearms for carrying tool-making gesturing intricate manipulations ability to walk upright large brains Link

What are the three most significant unique human characteristics?

ability to walk upright large brains ability to make tools speech

Why did scientists used to think that larger brains were the first uniquely human characteristic?

bigger brains precondition for higher intelligence

intelligence precondition for tool invention, making, and speech

Which of these three differences do scientists today believe emerged first?

upright posture but brain size remained unchanged for millions

of years

What does the Latin term "Homo sapiens" mean? Who does it describe?

"man the wise, the intelligent" modern humans like us!

How large is the average adult brain? [No jokes, please!]

Homo sapiens: 1200-1600 cc.

How large were the brains of Australopithecus afaransis?

Australopithecus: 350-500 cc

Comparative brain sizes

What is the difference between tool using and tool making? What does either indicate about intelligence?

improvisation or imitation vs. invention and planning

highly developed time sense for tool making

How long ago did the chimp line of evolution split from the human line? What is the evidence for this?

5-6 million years ago comparison of blood proteins and genes of

chimps and humans

What is the "foramen magnum"? How does it differ in humans and apes?

humans: entry of spinal chord in center of skull chimps: entry further back in skull—>head

thrust forward, not balanced—> limitation of size and weight

The foramen magnum

The foramen magnum compared

Brain size compared

Brains compared

QuickTime and aﾪTIFF (Uncompressed) decompressor

are needed to see this picture.

What significance did this difference have for the direction of human evolution?

brain growth depended on balance—>built-in limitation on brain-size of other apes

What percentage our DNA do humans share with chimps?

98% of human and chimp DNA is identical—> chimps and gorillas share 97%

Why did upright posture have to precede the evolution of upright brains?

larger brain size cannot be balanced or held up by ape posture—> neck and spine not able to support it

larger brain useless without free forelimbs to carry out instructions from brain

What was the most significant environmental change around 10-15 million years ago that favored apes with upright posture over more traditional apes? How did it do this "favoring"

long term drought reduced forests—>increased grasslands/savannah predator/prey advantages and disadvantages of

survival

What is the "key process" that drives evolution forward?

changes in environment—>upsets settled patterns of survival of plants, animals, humans

constant process of mutation—> reproduction never perfect—>mutation supplies new variations that might be beneficial in dramatically new circumstances

What survival advantages did a more upright posture give those apes who had it?

minimized skin exposure to harsh ultraviolet sunlight

cooled brains and conserved water

Are there other candidates for the title of "our earliest human ancestor"? Why don't we know for certain who the earliest actually is?

Ardipethecus ramidus—> 4.4 million years old & Australopithecus anamensis—> 4.2 million years old

new fossil discoveries very likely—> ALL SCIENTIFIC KNOWLEDGE IS PROVISIONAL!

Why is the Great Rift Valley in East Africa such a great place to explore for early human fossils?

Africa continent of origin during prehistory it was a wet region that

supported abundant plant & animal life during our time it is a dry region where spring

rains wash away surface sediment to expose the layers beneath

long-buried fossils are brought to light for those with the eyes to know what they are seeing

The Great Rift Valley

Name four of the best-known paleoanthropologists in the 20th century?

Louis Leakey Mary Leakey Richard Leakey Donald Johansen

Four Great Paleoanthropologists

What was the main staple of the Australopithecus diet?

vegetarian—>roots, tubers, nuts, berries occasional small rodents, lizards, insects

What was the probable key to the survival of Australopithecus against powerful, hungry predators?

social nature lived in groups of 20-30 safety in numbers

Who is "Lucy"? Why is she such a significant archaeological find?

she is the most complete skeleton of Australopithecus afaransis

"Lucy In the Sky With Diamonds" by Beatles playing on a cassette player the night she was discovered

Link

Why is the controversy about the fossilized bones of the "first family"?

remains of 13 individuals—> 9 adults & 4 children

200 fragments dramatic disparity between male and female

height—> sexual di-morphism or separate species?

Link

How does Lucy's lower jawbone (mandible) show she is an evolutionary midpoint between the other apes and modern Homo sapiens?

smaller jaw size indicates different diet different diet indicates different lifestyle and

ecological niche

The Change in Teeth

Change in Jaws