Ch. 19 The Neogene World

Transcription

1 Ch. 19 The Neogene World Neogene Period includes Miocene, Pliocene and Pleistocene epochs Beginning of Holocene was approx. 12,000 years ago 12,000 years Cenozoic Neogene 24 Paleogene 65 Holocene Pleistocene Pliocene Miocene Oligocene Eocene Paleocene Earth History, Ch. 19 1

2 Today s outline Glaciation Human evolution Earth History, Ch. 19 2

3 Continental glaciation Early Neogene climate was relatively mild In mid-pliocene time, ~3.2 million years ago, modern ice age began Ice age continues today, although glacial maxima and minima are cyclical, and we are now in an interglacial episode Earth History, Ch. 19 3

4 Northern Hemisphere continental glaciers Earth History, Ch. 19 4

5 Continental glaciation Bering Land Bridge was ice-free and a corridor for faunal interchange between North America and Asia Earth History, Ch. 19 5

6 Waxing and waning of glaciers High frequency glacial and interglacial cycles: Periodic changes in the tilt of Earth s axis relative to plane of orbit Periodic changes in the orbit itself, due to gravitational pull of other planets Cycles can be documented through oxygen isotope records Waxing and waning has displaced plant ecosystems by up to 20 latitude Earth History, Ch. 19 6

7 Oxygen isotope record (these should be positive numbers) Earth History, Ch. 19 7

8 Displacement of floral ecosystems Earth History, Ch. 19 8

9 Origin of the Great Lakes and Lake Bonneville Retreat of glaciers after the most recent glacial interval left behind large basins that eventually filled with water Great Lakes formed within the past 10,000 to 15,000 years Lake Bonneville covered much of Utah; now the Great Salt Lake is a tiny remnant Earth History, Ch. 19 9

10 Great Lakes and Lake Bonneville Earth History, Ch

11 What was the ultimate cause of Pliocene-Pleistocene glaciation? Probably related to creation of Isthmus of Panama Modification of global ocean currents Separation of Atlantic and Pacific oceans resulted in dramatic cooling of Arctic Ocean water Earth History, Ch

12 Earth History, Ch

13 Human Evolution: Superfamily Hominoidea includes gibbons, man, and apes. Homo is the only genus in Family Hominidae; sapiens is the only species in the genus Homo. Earth History, Ch

14 Early origins Earliest hominoid fossils are from Africa, ~20 Ma (early Miocene) These early hominoids are probably ancestral to both modern hominids and pongiids, but fossil record is spotty mid- to late-miocene was a time of hominoid radiation throughout Africa and Eurasia (more apes then than now!) Earth History, Ch

15 Earliest hominids Sahelanthropus is an intermediate between early apes and first true hominids Known from Chad in beds 6-7 Ma Earliest true hominids appeared at ~5.3 Ma, the australopithecines Australopithecus, Paranthropus Australopithecus ( Ma) was intermediate in appearance between modern apes and humans (not an evolutionary intermediate): Males larger than females (4.5 ft vs. 3.5 ft) Brain size barely larger than modern chimp Bi-pedal, but spent much time in trees Earth History, Ch

16 Sahelanthropus tchadensis Discovered in 2002 by Dr. Michel Brunet Earth History, Ch

17 Australopithecus Lucy, a female of the species A. afarensis, found in 3.2 Ma beds In Ethiopia Earth History, Ch

18 Bi-pedal Australopithecus tracks preserved in volcanic ash, ~3.0 Ma, from Tanzania Earth History, Ch

19 Early Homo Australopithecus branched into at least two species (A. afarensis and A. africanus) earliest Homo originated from Australopithecus approximately 2.4 Ma By 2.0 Ma, at least two species of early Homo were in existence Earth History, Ch

20 Hominid stratigraphy Earth History, Ch

21 Early Homo Characteristics of early Homo: Large brain (800 cm 3 vs only 450 cm 3 for Australopithecus) Smaller teeth Ability to make and use stone tools Meat in diet Spent most of the time on the ground (not in trees) Earth History, Ch

22 Hominid brain capacity Earth History, Ch

23 2.5 Ma stone tools skull of Homo habilis Earth History, Ch

24 Brain size vs. mode of life Brain of all newborn primiates = ~10% of body weight Brain growth stops shortly after birth in monkeys and apes Brain growth continues for ~1 year in Homo Homo development is delayed relative to chimps and apes Delayed maturation of Homo requires significant parental care Parents must hold babies, thus arms not free to hold onto tree branches Earth History, Ch

25 Earth History, Ch

26 Brain size vs. mode of life Development of large brain may be related to climatic change in Africa (~2.5 Ma): Drying out of climate reduced forests Life on ground may have paved the way for prolonged parental care Bipedalism probably preceeded increase in brain size Earth History, Ch

27 Homo erectus Homo erectus evolved from early Homo approximately 1.6 Ma First hominid to migrate beyond Africa Peking Man, Java Man Looked similar to modern humans, but: Slightly smaller brain (1000 cm 3 vs 1400 cm 3 ) Narrower pelvis Earth History, Ch

28 Homo erectus Bones of an 11 or 12 year old boy (1.6 Ma) Earth History, Ch

29 Homo neanderthalensis Neanderthal fossils are known in Eurasia in beds ranging from 100,000 to 35,000 years old Probably originated from a European or Asian population of H. erectus or related species Fossils commonly found in cave deposits Probably practiced some form of religion Buried dead family members with food and tools Earth History, Ch

30 Neanderthal burial Earth History, Ch

31 Homo sapiens Homo sapiens (modern humans) originated in Africa ~150,000 ybp (presumably from an African popolation of H. erectus or related species) DNA from H. sapiens and H. neanderthalensis indicates that ancestral populations may have diverged by 500,000 ybp Earth History, Ch

32 Homo sapiens Homo sapiens seemingly stayed in Africa for several tens of thousands of years before migrating to Europe Oldest European fossils of H. sapiens are ~33,000 ybp about the same time H. neanderthalensis vanished Earth History, Ch