Transcript Document
Introduction to Evolution Chris Scott, Ph.D. Evolution and Diversity of Vertebrates Echinodermata Chordates Cephalochordata ANCESTRAL DEUTEROSTOME Urochordata Notochord Craniates Vertebrates Gnathostomes Osteichthyans Lobe-fins Myxini Common ancestor of chordates Head Petromyzontida Chondrichthyes Vertebral column Actinopterygii Jaws, mineralized skeleton Actinistia Lungs or lung derivatives Dipnoi Lobed fins Reptilia Limbs with digits Amniotic egg Mammalia Milk Tetrapods Amniotes Amphibia Derived Characters of Chordates • All chordates share a set of derived characters • Some species have some of these traits only during embryonic development • Four key characters of chordates: 1. 2. 3. 4. Notochord Dorsal, hollow nerve cord Pharyngeal slits or clefts Muscular, post-anal tail Dorsal, hollow nerve cord Muscle segments Notochord Mouth Anus Muscular, post-anal tail Pharyngeal slits or clefts Tiktaalik the “fishapod" Fish Characters Scales Fins Gills and lungs Tetrapod Characters Neck Ribs Fin skeleton Flat skull Eyes on top of skull Shoulder bones Ribs Neck Scales Head Eyes on top of skull Humerus Ulna Flat skull Elbow Radius Fin “Wrist” Fin skeleton • Tiktaalik could most likely prop itself on its fins, but not walk • The first tetrapods appeared 365 million years ago Cephalochordata Urochordata Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia Mammals are amniotes that have hair and produce milk Mammals have: – – – – Mammary glands, which produce milk Hair A high metabolic rate, due to endothermy A larger brain than other vertebrates of equivalent size – Differentiated teeth Early Evolution of Mammals Early Evolution of Mammals • Mammals evolved from reptilian synapsids • These reptiles arose during the Pennsylvanian Period (310 to 275 million years ago). A branch of the synapsids called the therapsids appeared by the middle of the Permian Period (275 to 225 million years ago). It was over millions of years that some of these therapsids would evolve many features that would later be associated with mammals. Hominins and the Evolution of Humans Primates • The mammalian order Primates includes lemurs, tarsiers, monkeys, and apes • Humans are members of the ape group Derived Characters of Primates • Most primates have hands and feet adapted for grasping, and flat nails • Other derived characters of primates – A large brain and short jaws – Forward-looking eyes close together on the face, providing depth perception – Complex social behavior and parental care – A fully opposable thumb (in monkeys and apes) Living Primates • There are three main groups of living primates: I. Lemurs, lorises, and pottos II. Tarsiers III. Anthropoids (monkeys and apes, including humans) • The first monkeys evolved in the Old World (Africa and Asia) • In the New World (South America), monkeys first appeared roughly 25 million years ago • New World and Old World monkeys underwent separate adaptive radiations during their many millions of years of separation (a) New World monkey: spider monkey (b) Old World monkey: macaque Apes • The other group of anthropoids consists of primates informally called apes • This group includes gibbons, orangutans, gorillas, chimpanzees, bonobos, and humans • Apes diverged from Old World monkeys about 20–25 million years ago (a) Gibbon (b) Orangutan (c) Gorilla (d) Chimpanzees (e) Bonobos (d) Chimpanzees Last Common Ancestor for Humans and Chimpanzees: 7 Million years ago Lemurs, lorises, and bush babies Tarsiers ANCESTRAL PRIMATE Old World monkeys Gibbons Orangutans Gorillas Chimpanzees and bonobos Humans 60 50 20 30 40 Time (millions of years ago) 10 0 Anthropoids New World monkeys What does Hominin mean? • Hominin is a creature that paleoanthropologists have agreed is human or a human ancestor • Hominins include all of the Homo species (Homo sapiens, H. erectus , H. heidelbergensis), all of the Australopithecines and other ancient forms like Paranthropus and Ardipithecus Hominin Timeline Evidence of Bipedalism from the fossilized skull alone Comparison of Hip and Foot Bones longer ape pelvis is adapted for quadrupedal locomotion Evidence that Hominins walked upright 3.5 million years ago Footprints found near Lake Turkana, Kenya, show that human foot shape and gait had been achieved 1.5 million years ago SCIENCE, VOL 323, ISSUE 5918, pages 1197-1201 (Feb. 27, 2009) Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya SCIENCE, VOL 323, ISSUE 5918, pages 1197-1201 (Feb. 27, 2009) Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya Hominin • Hominin comprises the genera Homo, and the two species of the genus Pan (the Common Chimpanzee and the Bonobo), their ancestors, and the extinct lineages of their common ancestor Ardipithecus ramidus Between 1993 and 2003 bones of numerous Ardipithecus ramidus specimens were found in Ethiopia Ardipithecus ramidus October 1, 2009, paleontologists formally announced the discovery of the relatively complete A. ramidus fossil skeleton first unearthed in 1994. The fossil is the remains, dated 4.4 million years old, of a small-brained 110 lb, 3 foot 11 inch female, nicknamed "Ardi", and includes most of the skull and teeth, as well as the pelvis, hands, and feet. Researchers infer from the form of her pelvis and limbs and the presence of her abductable hallux, that she was a facultative biped: bipedal when moving on the ground, but quadrupedal when moving about in tree branches. Based on enamal thickness the teeth suggest she was an omnivore – her dental makeup is more generalized than those of modern apes Ardipithecus ramidus http://www.sciencemag.org/content/326/5949/60.2.full Youtube version Visual Reconstruction of Ardi movement Australopithecus afarensis Nickname: Lucy's species Where Lived: Eastern Africa (Ethiopia, Kenya, Tanzania) When Lived: Between about 3.85 and 2.95 million years ago (900,000 thousand years!) Features: 4 foot 11 inches; 100 lbs; combination of bipedal and tree climbing abilities; small brain; dental structure of omniovore Homo habilis (handy man) Early Homo • The earliest fossils placed in our genus Homo are those of Homo habilis, ranging in age from about 2.4 to 1.6 million years • Stone tools have been found with H. habilis, giving this species its name, which means “handy man” Homo habilis (handy man) • • • • Earliest known species of the hominin group that has the Homo genus Lived from approximately 2.33 to 1.4 million years ago Some fossils of H. habilis are found with shaped stone tools Homo habilis has often been thought to be the ancestor of the more gracile and sophisticated Homo ergaster, which in turn gave rise to the more human-appearing species, Homo erectus. • In 2000 a relatively late 1.44 million-year-old Homo habilis and a relatively early 1.55 million-year-old Homo erectus from the same area of northern Kenya challenged the conventional view that these species evolved one after the other • Instead, this evidence - along with other fossils - demonstrate that they co-existed in Eastern Africa for almost half a million years! 1.7 MY old Fossil of Homo ergaster Homo ergaster characteristics • Fossils from 1.9 to 1.5 MYA show a new stage of hominin development • H. ergaster had a bigger brain than H. habilus • H. ergaster had long slender legs with hip structure adapter for walking • H. ergaster fingers were shorter and straighter, implying lack of tree climbing • Sexual diamorphism is reduced • Tooth structure implying more meat eating Homo erectus Homo erectus (upright man) is an extinct species of hominid that lived about 1.9 million to 143,000 years ago (1.75 million years!!!) The species originated in Africa and spread as far as India, China and Java. Homo erectus, female. Reconstruction based on ER 3733 by John Gurche, front view Homo erectus Features: average height is 5 foot 9 inches, weight was about 150 lbs; oldest known early humans to have possessed modern human-like body proportions with relatively elongated legs and shorter arms compared to the size of the torso. These features are considered adaptations to a life lived on the ground, indicating the loss of earlier tree-climbing adaptations, with the ability to walk and possibly run long distances. Compared with earlier fossil humans, note the expanded braincase relative to the size of the face. The appearance of Homo erectus in the fossil record is often associated with the earliest handaxes, the first major innovation in stone tool technology. Homo erectus Range: Generally considered to have been the first species to have expanded beyond Africa, Homo erectus is considered a highly variable species, spread over two continents (it's not certain whether it reached Europe), and possibly the longest lived early human species - about nine times as long as our own species, Homo sapiens, has been around! Homo erectus Homo heidelbergensis 700,000 – 200,000; first early human species to live in colder climates, it was the first early human species to routinely hunt large animals. This early human also broke new ground; it was the first species to build shelters— creating simple dwellings out of wood and rock. Homo heidelbergensis • Comparison of Neanderthal and Homo sapiens DNA suggests that the two lineages diverged from a common ancestor, most likely Homo heidelbergensis, sometime between 350,000 and 400,000 years ago – with the European branch leading to H. neanderthalensis and the African branch to H. sapiens Homo neanderthalensis Homo neanderthalensis was a living species from at least 400,000 to 30,000 million years ago Homo neanderthalensis • The ancestors of Neanderthals left Africa about 400,000 to 800,000 years ago • Neanderthals evolved over the millennia mostly in what are now France, Spain, Germany and Russia • They were thick-boned with a larger brain (comparable to humans, stronger than humans, they buried their dead, and they made hunting tools • Neanderthals went extinct, or were simply absorbed into the modern human population, about 30,000 years ago Homo sapiens: Out of Africa • Our species is called Homo sapiens • During a time of dramatic climate change 200,000 years ago, Homo sapiens evolved in Africa • Like other early humans that were living at this time, Homo sapiens gathered and hunted food, and evolved behaviors that helped them respond to the challenges of survival in unstable environments Homo sapiens Compared to other members of the genus Homo, Homos sapiens have: 1. A lighter build of their skeletons 2. Large brains 3. A thin-walled, high vaulted skull 4. A flat and near vertical forehead 5. Much less (if any) heavy brow ridges 6. Smaller noses 7. Less heavily developed jaws 8. Smaller teeth Homo sapiens and Homo neanderthalensis • The earliest known Homo sapiens in Europe lived in a southern Italian cave 45,000 years ago • Homo sapiens were also in what is now the U.K. about 44,000 years ago • Neanderthal fossils have been found in Europe and Asia as recently as 28,000 years ago • These studies show that Homo sapiens quickly spread over Europe and coexisted with Neanderthals Homo sapiens and Homo neanderthalensis • In May 2010 (Science magazine) a draft sequence of the Neanderthal genome was published • Genomic comparison confirmed Homo sapiens and Homo neanderthalensis interbred • Most, if not all, of the interbreeding took place in the Middle East, while modern humans were migrating out of Africa and spreading to other regions • If your heritage is non-African, you are part Neanderthal! Homo sapiens and Homo neanderthalensis • The Homo sapiens/Neanderthal combination likely enabled interbred Homo sapiens to survive in harsh, cold regions that Neanderthals previously had adapted to • Variability is very important for long-term survival of a species -- every addition to the genome can be enriching • Humans first arrived in the New World (North and South America) sometime before 15,000 years ago by travelling across the Alaska-Russia land bridge • In 2004, 18,000-year-old fossils were found in Indonesia, and a new small hominin was named: Homo floresiensis A timeline for some selected hominin species • Homo sapiens were the first animal group to show evidence of symbolic and sophisticated thought • Chimpanzees regularly crack open hard-shell seeds and nuts with a stone hammer against a stone or wooden anvil; and they'll carry the appropriate rocks over a good fraction of a kilometer for the purpose. • A chimp breaks off a long grass stalk or a reed so she may use it later, hundreds of meters away, more than an hour in the future, to lure delectable termites out of a log or termite mound. Gorilla using a stick to test water depth In 2002, a 77,000-year-old artistic carving was found in South Africa Timeline • • • • • • • • • • • • • • • Approximate age of the Universe: 14 billion years................................ 14,000,000,000 Approximate age of the Earth: 4.5 billion years........................................4,500,000,000 Approximate age of life on this planet: 3.5 billion years....................3,500,000,000 First tetrapods (Tiktaalik, the first “fishapod”)..............................................365,000,000 Permian Great Extinction.........................................................................245,000,000 Evolution of the first mammals and.............................................................240,000,000 K-T Great Extinction (end of the dinosaurs).............................................65,000,000 Earliest fossil evidence of the first hominin (Sahelanthropus tchadensis).......6,500,000 Age of “Ardi” (Ardipithecus ramidus) fossils....................................................4,400,000 Earliest fossils of the genus Homo (Homo habilus, “handy man”)...................2,400,000 Approximate age of our species Homo sapiens.................................................200,000 Approximate age of the first human civilizations: less than 8,000 years ago..........8,000 Approximate age of oldest discovered book*: .......................................................4,000 Start of mass produced books using the Gutenberg press (~1440 AD)....................572 Number of years the iPad has been available to the public...........................................2 * The Epic of Gilgamesh is an epic poem recorded on 12 clay tablets from Ancient Mesopotamia (now Iraq)