The Evolution of Humans The Evolution of Humans

The Evolution of Humans

The Evolution of Humans An Evolutionary Play in Five Acts · · · Act one: The Cro Magnons and the Neanderthals Act two: The Great Leap Forward Act three: Early Homo An interlude Act four: The Australopithecines Act five: The First Steps

The Evolution of Humans The Ecological Theatre · The Stage: East Africa. . .

The Evolution of Humans

The Evolution of Humans The Ecological Theatre · The Stage: East Africa · The Setting: A time of unrest. . .

The Evolution of Humans The Ecological Theatre · The Stage: East Africa · The Setting: A time of unrest. . . · Geologically… · The rift zone - uplifts, rifting, volcanoes (an "aulacogen")

The Evolution of Humans

The Evolution of Humans

The Evolution of Humans Is 7 million years enough?

The Evolution of Humans The Ecological Theatre · The Stage: East Africa · The Setting: A time of unrest. . . · Geologically… · The rift zone - uplifts, rifting, volcanoes · Climatically… · A series of glaciations · Global climate change · Changes in sea level

The Evolution of Humans Act one: The Cro Magnons and the Neanderthals

The Evolution of Humans • What about the Neanderthals?

The Evolution of Humans • What about the Cro Magnons?

The Evolution of Humans The Neanderthals and the Cro Magnons… · Climate change? · Hybridization? · Ecological competition? · “Conquest”?

The Evolution of Humans • What about the Cro Magnons?

The Evolution of Humans

The Evolution of Humans Act two: The Great Leap Forward

The Evolution of Humans Act two: The Great Leap Forward · Homo sapiens (behaviorally modern humans) appeared sometime between 160 tya and 40 tya · Fossils from East Africa have been described as a new subspecies Homo sapiens idaltu, and dated about 160 tya… · The development of behaviorally modern humans is sometimes referred to as the “Great Leap Forward”. . .

The Evolution of Humans The Great Leap Forward reasons for the Great Leap Forward…

The Evolution of Humans The Great Leap Forward • Due to evolution of a mechanism that allows speech and language? · Characterized by the appearance of. . . • Use of symbols. . . · Complex tools. . . · Innovations in hunting techniques and strategies. . . · Increased population size, development of social systems. . . · Houses, boats, long distance trade, ornaments · Art, music, rituals. . .

The Evolution of Humans Act three, scene one: Early Homo · Homo heidelbergensis

The Evolution of Humans Act three, scene one: Early Homo · Homo heidelbergensis (800 - 100 tya) · formerly referred to as “archaic” H. sapiens) · their skeletal characteristics are intermediate between H. erectus and H. sapiens · Homo heidelbergensis appeared first in Africa, then later in Europe and western Asia. · Homo heidelbergensis is thought to be ancestral to Homo neanderthalensis (250 tya - 30 tya) and to Homo sapiens (at least 195 tya - present)

The Evolution of Humans Act three, scene one: Early Homo · Homo erectus (1. 9 mya - 0. 2 mya) · first described in 1891, before the existence of the australopithecines was known · Variously known as Java Man, Peking Man, Turkana Boy…

The Evolution of Humans “Peking Man”

The Evolution of Humans “Turkana boy”

The Evolution of Humans Act three, scene one: Early Homo · Recent interpretations of Homo erectus include two other species (Homo ergaster and Homo antecesor) within Homo erectus · In this view, Homo erectus is a widespread and geographically variable species

The Evolution of Humans Act three, scene two: Early Homo · Actors include Kenyanthropus platyops (about 3. 5 mya), Homo habilis (2. 3 -1. 6 mya), and Homo erectus (1. 9 mya 200 tya) · The simple interpretation ignores Kenyanthropus, places Australopithecus afarensis as ancestral to Homo habilis (giving Lucy the honor of being the ancestor of the genus Homo), and places Homo habilis as ancestral to Homo erectus. · A more complex interpretation recognizes Kenyanthropus as having features more like Homo erectus, and places it as ancestral to Homo erectus, leaving Homo habilis as a sterile side branch.

The Evolution of Humans

The Evolution of Humans Kenyanthropus platyops and Homo habilis

The Evolution of Humans • The interlude… • Morphological • Ecological

The Evolution of Humans • Morphological trends during the evolution of hominids: • Morphological features associated with bipedalism: • Foramen magnum directed downward • Pelvis is shorter, flatter, and broader • Pelvic canal expands • Acetabula point downward • Legs longer, arms shorter

The Evolution of Humans • Pertinent morphological trends during the evolution of hominids: • Other trends. . . – Body size increases – Cranial capacity increases • Australopithecus afarensis: 400 ml • Australopithecus africanus: 440 ml • Homo habilis: 600 ml • Homo erectus: 850 ml • Homo heidelbergensis: 1200 ml • Homo sapiens: 1350 ml • Homo neanderthalensis: 1200 -1700

The Evolution of Humans • Ecological and behavioral trends during the evolution of hominids: • Habitat changes from forest to savanna, associated with changing climate in east Africa, but… • Geological and climate change is complex and does not always correspond to changes in hominids • Social organization - probably small social groups • Development of tool use (in Homo habilis and Homo erectus) • Domestication of fire (probably in Homo erectus)

The Evolution of Humans Act four: The Australopithecines: · Australopithecus plays a central role in the phylogeny of hominids. This was the first genus to branch into several species. · The earliest member of this genus is Australopithecus anamensis (4. 0 mya). · The immediate descendant of Australopithecus anamensis is Australopithecus afarensis (3. 9 - 3. 0 mya). · Of the australopithecines, Australopithecus afarensis ("Lucy") is the most famous and best known paleontologically.

The Evolution of Humans

The Evolution of Humans Act four: The Australopithecines: · Australopithecus afarensis is thought to be ancestral to A. africanus (2. 5 mya). · After A. afarensis and A. africanus, several species appear, including a group of 3 to 5 species that are now called the “robust australopithecines” and placed in the genus Paranthropus.

The Evolution of Humans Act four: The Australopithecines

The Evolution of Humans Act five: The First Steps · A linear sequence of species leads from the divergence from chimps about 7 mya to the appearance of Australopithecus about 4 mya · Sahelanthropus tchadensis (7 mya) · Orrorin tugenensis (6 mya) · Ardipithecus kadabba (5. 2+ mya) · Ardipithecus ramidus (4. 4+ mya) · These actors exhibit a progression of characteristics that indicate they are part of the main line of hominid evolution · Were they bipedal?

The Evolution of Humans Sahelanthropus tchadensis