earth history geol 2110 the dawn of humans and the effects of climate on civilizations the...

Earth History GEOL 2110

The Pleistocene Epoch The Dawn of Humans and the

Effects of Climate on Civilizations

Major Concepts• Climatic changes produced distinctive flora and fauna that was

adapted to cold weather• Among flora were the expansion of grasslands, tundra, boreal

spruce forests, and hardwood forests• Among the fauna, cold adapted mammals such as mastodons,

mammoths, wooly rhinos, giant bison, ground sloths, and saber-toothed cats flourished.

• The first hominids appeared about 7 Ma; the genus homo, bipeds with big brains, appeared around 1.8 Ma just as glaciation took off.

• The first modern humans (homo sapiens) appeared about 90,000 ybp in East Africa and expanded to Asia and Europe by 40,000 ybp. Expansion to the Americas occurred round 12,000 as the Laurentide Ice sheet began to retreat

Effect of Glaciation on Flora

Effect of Glaciation on Flora

Buried Forest at Two Creeks, WI

12,000

10,500

Fossil Boreal Spruce Forest

Effect on Fauna40,000 ybp La Brea Tar Pits, Los Angeles

Effect on FaunaMammals at the La Brea Tar Pits

HerbivoresColumbian mammoth (Mammuthus columbi)American mastodon (Mammut americanum)Harlan's ground sloth (Paramylodon harlani)Jefferson's ground sloth (Megalonyx jeffersonii)Shasta ground sloth (Nothrotheriops shastensis)Giant bison (Bison latifrons)Ancient bison (Bison antiquus)American camel (Camelops hesterus)Stilt-legged llama (Hemiauchenia macrocephala)Western horse (Equus "occidentalis")Mexican horse (Equus conversidens)Peccary (Platygonus compressus)Pronghorn (Antilocapra americana)Dwarf pronghorn (Capromeryx minor)California tapir (Tapirus californicus)Elk (wapiti) (Cervus canadensis)Deer (Odocoileus sp.)

CarnivoresShort-faced bear (Arctodus simus)Brown bear (Ursus arctos)Black bear (Ursus americanus)Scimitar cat (Homotherium serum)Sabre-toothed cat (Smilodon fatalis)American lion (Panthera leo atrox)Jaguar (Panthera onca augusta)American cheetah (Miracinonyx inexpectatus)Cougar (Puma concolor)Bobcat (Lynx rufus)Dire wolf (Canis dirus)Gray wolf (Canis lupus)Coyote (Canis latrans)WeaselOmnivoresHuman (La Brea Woman)RaccoonSkunkBrown bear

Fig. 16.29Evolution of Primates

Tetonius, an early primate of the Early (warm) Eocene,Western North America

Similar to present day lemurs of Madagascar

Cooling through the Cenozoic limited their range to Africa

Fossils are rare due to their upland existence

Africa -Home of Human Evolution

Aegyptopithecus, Early apeOligocene (~ 30 Ma), Egypt

Sivapithecus , Ancestor to Orangutans & Humans Miocene (8 Ma), Pakistan

Mid-Cenozoic Apes develop Hominoid attributes

Molecular evidenceBiological Similarities between Humans and Apes

• chromosome structure - mostly identical• amino acid sequences for hemoglobin (all 287) are identical in

chimpanzee and humans (we differ from gorilla in only two amino acids, and from orangutan in only four)

• comparison of all genetic material reveals that humans differ from chimpanzees in only 1.6% of their DNA (gorillas differ by 2.3% from chimpanzees)

• genetic data also suggests that the separation from the gorilla lineage occurred about 10 million years ago and the human lineage split from that leading to chimpanzees about 7 million years ago

• genetically humans are a lineage in the anthropoid class - we are closely related to great apes

Anatomical Differences with Apestwo major differences make humans unique• balanced bipedal posture

– head is balanced on the spinal column– rib cage is more barrel shaped– backbone is re-curved and the pelvic structure is rotated– our legs are twice as massive compared to our bodies as gorillas

and our arms only 2/3 as massive– our hind limbs (legs) are proportionately longer and altered to

permit striding gait• large brain to body weight ratio

– unlike in apes and other mammals, the human brain continues to grow for a year after birth

– our huge mental capacity allowed for the development of language and a unique culture

Evolution of HumansHomonids split from Ape relatives 6-7 Ma

Lucy

4 Species of HomonidsLiving Side-by-Side

•Between 6 and 3 Ma the record is patchy, but:• Ardipithecus from about 5.8 - 4.4 Ma• Australopithecus (including Lucy):• big molar teeth and jaw structure• hips intermediate between chimps

and humans

Genus Australopithecus Appears 4.2 Ma

Australopithecus afarensisLucy

About 3.5 My old

Lucy

20 yrs old3.5’ tall

Laetoli footprints (3.5 million years old)

•Paranthropus (large toothed)• co-existed with genus Homo • go extinct around 1.3 Ma with a number of other

African mammals

Australopithecus Genus Splits at 2.7 M into Homo and Papanthropus lineages

Homo erectus appears about 1.6 Ma, with strong resemblance to modern humans • limbs designed for long-distance running• Disperses out of Africa around 1.0 Ma to

Dmanisi, Georgia• Takes on the behavior of large carnivores• Disperses as far as China and Indonesia• Like apes, grew up early and died young• Developed the hand axe• First use of fire around 700,000 years ago

Homo habilis (“The Handy Man”) fossils about 1.75Ma• stone tool artifacts attributed to

Homo appear around 2.6 Ma• larger brain, about 700 to 1000 cc in

capacity

• Humans are the only species that cook their food

• Homo erectus emerged about two million years ago as a result of this unique trait.

• Cooking had profound evolutionary effect because it increased food efficiency which allowed human ancestors to spend less time foraging, chewing, and digesting.

• H. erectus developed via a smaller, more efficient digestive tract which freed up energy to enable larger brain growth.

• Cooking and control of fire generally affected species development by providing warmth and helping to fend off predators which helped human ancestors adapt to a ground-based lifestyle.

• Humans are highly evolved for eating cooked food and cannot maintain reproductive fitness with raw food

Dmanisi

‘Ubeidiya, Israel 1.4 my

Mojokerto 1.8 my ?

Sangiran 1.66 my ?

Nihewan, China 1.6 my

Spain1.2 my

Italy 0.8 my

Homo ErectusDisperses Out of Africa

Tools since 2.6 MaPerhaps marking the first appearance of Genus Homo

Homo Erectus ~1.7 Ma (onset of continental glaciation)migrate to Java and China

Neanderthals disperse throughout Africa and Europe500,000 to 30,000 years ago

Homo Sapiens greatly expanded in numbers and migrated out of Africa around 75,000 years ago

Migration into the Americas

Bering Land Bridge Canadian Corridor Panama Land Bridge

Climate effects on Humanity since the glaciers left

Lush environment in the Nile and Tigris River Valleys

Large Mammals go extinct due to overhunting and warming of climate

Drought and famine hit the Mediterranean

Greenland settled

Famine & disease in Europe, Greenland abandoned

Potato Famine

North Shore Field Trip

Sunday, May 4, 2014

DEPART at 8:00AM