The Descent of Man MHS Science The History of Biological Sciences A Little Stroll Through An Odd Assortment of Ideas, Facts, Theories, and Debates Concerning The Descent of Man
Charles Darwin Buffon Alfred Russel Wallace ATTENTION!!! Georges Cuvier This is NOT a discussion on evolution and the scientists associated with it. It is simply some of their ideas applied to our species. Thomas Huxley Linnaeus Lamarck Charles Lyell
New discoveries are always just around the corner. As members of an educated public, you will understand and perhaps even participate in the debate and just as important, the development of a more complete comprehension of Homo sapiens, the animal, as well as Homo sapiens, the human being.
ONTOGENY RECAPITULATES PHYLOGENY Ontogeny The history of the development of an individual organism Phylogeny The evolutionary history of a species; evolutionary relationships of organisms; a “family tree”
The Mammalian Brain • Large and versatile • Rely less on genetically programmed instinct • Adjust more readily to environment - basing behaviour on experience and learning • The cerebrum (learning center and region of conscious thought) relatively larger • Corpus callosum has been added Look at me…I’m a mammal
Mammalian Points of Interest Fossil records indicate mammals arose from therapsids (197 to 225 million years ago) Three (3) types of mammals: Placental (uterine embryonic development) Marsupials (birth immature young - pouch development) Monotremes (hairy egg layers)
PRIMATES Monkeys - Apes - Hominids Tree shrews Tarsiers Lemurs Loris and Potto Old World New World Ceboidea(prehensile tail) Cercopithecoidea Gibbons, Orangutans, Gorillas, Chimpanzees, Hominoidea
Sifikas Lemur Gorilla Orangutan Chimpanzee
Femur articulation Skull + Dentition Pelvic Girdle Hands and Feet Torso - Rib Cage Long Bones - Robust Chimpanzee Skeleton Monkey Skeleton
Skeletal Close-Up... From trees to terrestrial Quadruped to Biped
About 4.4 millions years ago, a different type of primate emerged. Paleontologists classify the first bipedal primates as hominids. These first hominids had not yet developed the large brain, teeth structure, and skeletal features we identify as Homo. Instead, they predate, and sometimes overlap the first Homo species. They are known as the Australopithecines.
Australopithecines Gracile Australopithecines Robust Australopithecines Australophithecus afarensis Australopithecus robustus Australopithecus boisei Australopithecus africanus
Both gracile australopithecines were: 1. Small in stature (1 - 1.5 meters) 2. Similar brain size/cranial capacity (400 - 500 ml) 3. Light body structures And they call me “Taung child”. I am “Lucy” A. afarensis A. africanus More ape-like Predates A. africanus by 1.5 my Bi/Quadrupedal Bipedal - musculature is similar to baboons Found before A. afarensis
It is not known how these species directly affected human evolution. However, there are many theories: A. afarensis A. afarensis Common ancestor A. afarensis A. africanus Homo A. africanus A. boisei Both robust A. robustus A. africanus Homo A. boisei A. robustus Homo
At around two million years ago... Homo habilis (Evolutionary and technological breakthroughs) Habilis means handy-man Cranial capacity 600 - 800 ml First stone tools developed
At around one million years ago... Homo erectus (Evolutionary, technological and cultural adaptations) H. erectus and H. sapiens practically identical below the neck. . Cranial capacity 750 - 1250 ml and foreheads begin to develop as a result of a growing frontal lobe (foresight - reasoning - concentration) Nothing.. Hand ax, weapons, big-game hunting and the use of fire Habitual erect posture and efficient bipedal gait
At around 75 to 30 thousand years ago... Homo sapiens neanderthalensis Homo sapiens sapiens It is far from easy to put these fellas in their place Cranial capacity 1250 - 1750 ml (Neandertal) - sloping forehead 1200 - 1600 ml (Modern humans) Neandertal variations: Larger Birth canal and wider pelvic width - longer gestation? Bones considerably more robust No Neandertal traits fall totally outside the variation range of modern humans.
SKULLS A Side View Note: Temporal bone Frontal bone (slope) Occipital bone Maxilla and Mandible
SKULLS A. africanus H. habilis A Frontal View Note: Frontal bone Brow ridge Zygomatic arch Maxilla H. erectus H. sapiens
A widely accepted theory (to date) Based on: Dentition Skull anatomy Fossil location Mitochondrial DNA Long bone analysis Pelvic girdle Radioactive dating
Evolution: The Human Adventure Life 3.5 billion years ago Fossil vertebrate record 500 million years Placental mammal radiation to the beginnings of the primate order more than 60 m.y.a. New/Old World divergence 40 m.y.a. First hominoid 20 m.y.a. Disputed: 10 - 5 m.y.a. first hominid (human family) Australopithecus afarensis 5 m.y.a. The genus Homo emerging 2 m.y.a. Homo erectus 1 m.y.a. Homo sapiens sapiens 100 000 - 40 000 years ago
Hominid evolutionary development has created Homo sapiens, an animal with behavioural flexibility. But unlike any other organism on this planet we can infinitely mold our own behaviour through exercise of our own uniquely human creativity. Does this mean we have left the realm of biological evolution? No, but our profound ability to modify our environments has outdistanced our biological capacity to respond. How then can we be expected to cope with the new biological pressures of the modern technological world?
Clearly, the biggest dangers are the cultural ones we have created for ourselves: POLLUTION, OVERCROWDING, WAR, RESOURCE MISMANAGEMENT, and so forth. Equally as clear, the only viable answers are also cultural ones. As human beings, we possess the capability to remake the world - for better or worse. The choices are ours.