Exam 1 Study Guide
Exam 1 Study Guide 1. Know the traditional classification of the Hominoidea as well as the new molecular-based classification as we discussed it in class. Know what animals are what in both schemes. Why was the change to the new classification necessary? Know the scientific name of all extant large-bodied hominoids. Traditional Classification: Superfamily: Hominoidea (hominoids) Families: Hylobatidae (lesser apes - gibbons, siamangs) Pongidae (great apes - orangutan, gorilla, chimpanzee, Bonobo) Hominidae (hominids - humans) Molecular-Based Classification: *Chimpanzees more Superfamily: Hominoidea (hominoids) genetically similar to humans Families: Hylobatidae (lesser apes - gibbons, siamangs) than to other apes* Hominidae (hominids - all great apes) Subfamilies: Ponginae (orangutans) Homininae (African great apes & humans) Tribes: Gorillini (gorillas) Panini (chimps, bonobos) Hominini (humans) Human = Homo sapien Chimpanzee = Pan troglodytes Bonobo = Pan paniscus Gorilla = Gorilla gorilla Orangutan = Pongo pygmaeus Gibbon/Siamang = Hylobates 2. What is paleontology? What is the discipline really concerned with (as we discussed in class)? What is the role of comparative anatomy and molecular biology in doing paleontology? Paleontology - Science concerned with reconstruction of lineages, understanding the nature of relationships within and among lineages, based primarily on the fossil record, but also on genetics (molecular biology) and comparative anatomy 3. As a science, paleontology is hampered by both theoretical and practical limitations. Discuss as presented in class. Practical Limitations of Paleontology: Incomplete biological data - skeletal elements & what can be derived from them Fragmentation, incompletion, & distortion of fossils, Gaps in fossil record - temporal & geographical gaps Inadequate sample sizes, chronology, and knowledge of paleoecology Theoretical Limitations of Paleontology: Can’t go back in time and observe events, Can’t duplicate events experimentally (“Physics envy”) 4. What is homology and why is this concept so important to classification and reconstructing phylogenies? Discuss how homologies are established. Homology - Similarity of STRUCTURE in tissues, organs, skeletal elements, or genetics that is traceable to a common ancestor Criteria for Identifying Homology: 1. Identify what feature is present in the last common ancestor (LCA) 2. Trace feature in a lineage from target taxa to LCA 3. Is feature consistently present? 4. Ontogeny of trait (How does the trait develop? Is it present in juveniles?)
5. Discuss cladisitics as a methodology for establishing phylogenetic relationships. How are polarities established? What are some limitations of cladistics? Include a discussion of stratophenetics. Cladistics - grouping on the basis of shared derived characteristics only (apomorphs) Four principles to judge polarity - whether a trait is plesiomorphic or apomorphic: 1. Last Common Ancestor (LCA) - most important principle 2. Outgroup comparison 3. Commonality 4. Ontogeny - general recapitulation principle (developed by Haeckel) - during development some primitive evolutionary traits may be present (Ex: gill slits and tails in human fetuses) Limitations: Developed for extant taxa - difficult to apply over time (biological history) Intermediates in fossil record difficult to handle (Ex: A. afarensis canine form) Parsimony - reconstruct relationships with fewest reversals & parallelisms possible = basis of cladistics Assumes the irreversibility of evolution & disregards functional shifts (change in adaptive conditions) Chronology irrelevant = biggest problem Stratocladistics = Modified Cladistics (Gingerich) Basis = cladistics (shared-derived traits) Chronology & geography taken into consideration Possibility of reversals & parallelisms considered Careful use of phenetic data 6. What is the synthetic theory of evolution? Out of what perspectives was it developed? What are its major tenants? Synthetic Theory of Evolution (STE) - brought together 2 perspectives: Genetic & Darwinian Mutation - the only creative evolutionary mechanism - only way to create new alleles Natural selection - primary mechanism of change Evolution - basis of genetic change - change in genes or gene frequencies Emphasis on populations as the unit of study - individuals do not evolve Macroevolution (origin of new species) = result of long-term microevolution (processes of change w/i a species 7. On what evidence did the punctuated equilibrium model challenge the STE? Provide an assessment of how effective this challenge is. In your opinion does it require replacing the STE? Why or why not? Punctuated Equilibrium Model of Macroevolution (“Punk-eek”), Five Points: 1. Evolutionary change is never constant and gradual, but always sporadic (saltational) - stasis is the rule, change is relatively rapid 2. Speciation always by branching (cladogenesis), never by anagenesis 3. Cladogenesis very common in biological history (Gould: “Evolution is a bush, not a ladder”) 4. Significant evolutionary change only occurs during speciation events - small peripheral populations opportunity for biological novelty 5. Evolution = hierarchical process w/ 3 levels - molecular, microevolutionary (population), & macroevolutionary (species) - different mechanisms at each level - macroevolution not an expansion of microevolution, directed by species selection - selection on populations, not individuals (ex: mass extinctions due to abrupt ecological changes - dinosaur extinction (K/T boundary - Cretaceous/ Tertiary) Because the Punctuated Equilibrium Model of Macroevolution includes arguments based on faulty assumptions, I do not believe that it offers a sufficient replacement for STE. Punk-eek claims that microevolution and macroevolution are driven by different selection mechanisms. While microevolution is driven by natural selection, macroevolution is supposedly driven by “species selection,” but this mechanism is merely an invented term for large-scale natural selection. Natural selection works on individuals, no matter the number. A species is not a discrete entity which can be acted upon, but rather a collection of individuals. Even in the case of mass extinctions, I do not believe that species selection occurs. In these cases, species become extinct because the individuals within
the species do not have enough variation to adapt to changing conditions. Therefore, this represents a large-scale version of natural selection. Also, punk-eek argues that speciation always occurs by cladogenesis, but I believe that anagenesis, though harder to definitively identify, is also possible. Quantum evolution accounts for saltation in the fossil record, the rarity of transitional fossils, and also the role of peripheral populations. 8. Using information from the skull and dentition, discuss the differences between extant ape and hominin anatomy. Where appropriate, discuss how these features are interrelated (e.g. all the features associated with the canine). Differences in Dentition: The maxillary canines of apes are large, projecting, and conical with a sharp apex and marked distal cutting blade. These teath wear from rear, which hones the canine. Because the canines are so large, apes have a distinct maxillary diastema, which allows the jaw to occlude. There is marked sexual dimorphism in the size of ape canines, with the male canine being much larger. Apes use these large canines for defense, display behaviors related to the competition for females, and food processing. Because the canine is such an important and predominant part of the ape dentition, many other features of the ape morphology are related to it. These features can be called the ape “canine complex.” Hominin canines are reduced in size and lack all these features. They are incisor-like and wear from tip. Since the canines are smaller, there is no maxillary diastema. Sexual dimorphism is much reduced. The third mandibular premolar of apes has a different shape than the fourth, so ape premolars are called heteromorphic. The ape P3 is sectorial, with one large mesially rotated cusp. This unique shape is an adaptation which helps hone the enlarged ape canine, so is part of the canine complex. The human P3 has two cusps, just like the P4, so the premolars are homomorphic. The first maxillary incisor in apes is larger than the other incisor and angled forward. This adaptation may relate back to the apes’ diet, helping them pluck fruit from the trees with their teeth. The first maxillary incisor in humans is similar to the other incisors. Also relating to their diet of fruits and soft vegetation, apes have a thin layer of enamel on the occlusal surface of their molars. Humans, due to dietary differences, have thicker enamel. Differences in Skull: Ape jaws are prognathic, so protrude much more than human jaws. The ape nasoalveolar clivus also angles out much more than that of a human. This prognathism relates back to the enlarged ape canine. Since the canine root is so large, the ape jaw must angle out to supply the necessary amount of space. The supraorbital torus in apes relates back to this prognathism, providing structural continuity of the face. Because the ape maxilla protrudes out, the mandible has a receding mandibular symphysis. All of these traits relate back to the ape canine complex. Since human jaws are orthognathic, humans have a more vertical mandibular symphysis and a higher cranial base flexure index. In humans, a mental eminence (chin) replaces the ape simian shelf. While ape skulls are widest at the level of the cranial base, human skulls reach their maximum width much higher, at the temporal line. Humans have a much larger cranial capacity due to their larger brains. The foramen magnum is located more posteriorly in apes, which relates back to the angle of the spine in quadrupedal locomotion. Humans have a well developed articular tubercle, which is lacking in apes. Since apes have stronger temporalis and nuchal muscles, and some individuals have temporonuchal and sagittal crests to provide additional muscle attachment area. Apes also have a much more expanded mastoid area and nuchal plane, which allows attachment for their strong neck muscles. 9. Discuss in general what we know about the Miocene radiation of great apes. Be sure to focus on the genera mentioned in class (particularly Proconsul, Sivapithecus, and Dryopithecus). What are the changes over time in both morphology and geographic spread? The Miocene Epoch (23-5 mya) was a time of great adaptive radiation of apes. 17-18 mya there was permanent land contact between Africa and Eurasia, which allowed extensive faunal exchange (apes to Eurasia, elephants to Africa). During the early Miocene the climate was warm and wet, with extensive tropical forests. These conditions were perfect for apes, and ~14 genera & ~50 species of apes are known from that time. Later, around 14 million years ago, the Miocene climate began to change drastically. The temperature and precipitation dropped, causing the lush forests to shrink and fragment. Because of this ecological change, apes were forced to move into new niches, particularly the expanding grasslands. This move required adaptations in both behavior and morphology. For example, Gigantopithecus and early Australopithecus show thicker molar occlusal enamel, which would have allowed them to eat tougher foods which were available in the grasslands. All Miocene apes share hominoid
apomorphies, such as the Y-5 molar pattern and the coccyx. They also show cranial, mandibular, dental, and postcranial characteristics that are similar to extant apes (except maybe Sahelanthropus & Orrorin). Miocene Ape Genera: 1. Proconsul: E/M Miocene (23-14 mya), 12-13 species, 17-55 kg - Africa - earliest ape form! Ape-like crania, mandible & dentition, BUT lacks extant ape postcranial apomorphs intermembral index = 87 → no pectoral limb elongation, manus lacks elongation & curvature of metacarpals & phalanges - palmigrady, Carpus (wrist): long styloid process of ulna All monkey-like features! (Primitive, monkey-like postcranium, but no tail) Thus - generalized arboreal quadruped like monkeys, NOT – brachiator 2. Afropithecus: E/M Miocene, 1 species, 50 kg - Africa 3. Sivapithecus: M/L Miocene (15-7 mya), 2-3 species, 75 kg - W Asia - India (earliest ape in Asia) • Narrow interorbital region, oval orbit shape, concave lateral facial profile, Pongo subnasal morphology • All of these features are apomorphic for hominids • Thus Sivapithecus & Pongo = synapomorphs, Sivapithecus → early Pongo lineage 4. Dryopithecus: M/L Miocene (14-7 mya), 15-45 kg - Europe (earliest ape found in Europe) • Crania, mandibles, dentition, & postcrania are ape-like • limb proportions, manus, carpus brachiator/modified quadruped 5. Ouranopithecus: L Miocene (10-9 mya), 100 kg - SE Europe (Turkey/Greece) 6. Lufengpithecus: L Miocene (9-8 mya), 50 kg - China 7. Gigantopithecus: L Miocene - M Pleistocene (9-0.3 mya), 225 kg - India-China • Poorly known (4 mandibles, teeth, few postcranials), Asian or African ape? • 2 species (G. blacki = M Pleistocene of China; G. giganteus = L Miocene of India) • Largest ape that ever lived (large male ~ 300 kg) • Found at Homo erectus sites in China – nature of interaction unknown • Strange, cupping wear on molars similar to Ailuropoda (giant panda) – specialized bamboo feeding, possibly outcompeted by pandas • distal humerus suggests modified quadruped – but no solid knowledge of postcranial adaptations 8. Sahelanthropus: L Miocene (7 mya) - Africa (1 skull) One of the earliest possible hominins - anterior foramen magnum, no postcranial evidence Temporonuchal crest, prognathic face, brow ridge Reduced canine, no diastema 9. Orrorin: L Miocene (6 mya) - Africa (fragmentary postcranial) - Also possible early hominin Proconsul, Dryopithecus, Afropithecus, Lufengpithecus, Ouranopithecus all exhibit extant African Great Ape patterns of: • Broad interorbital area, roundish orbits, straight lateral facial profile, & African subnasal morphology • These features are all plesiomorphic for hominids (great apes) – all these taxa share sympleiomorphs 10. Provide an assessment of how the human pelvis, lower limb, foot and vertebral column are modified for obligate bipedalism. The bones of the hominin pelvis are shaped differently than an ape pelvis to provide an attachment site for the muscles necessary to bipedal movement. For example, in hominins the gluteus maximus, which provides powerful thigh extension during bipedal locomotion, attaches to the post-acetabular region of the iliac blade. In apes, this muscle is much less important, so the post-acetabular region is much less extended. Since the bipedal pelvis has to support much more weight than a quadrupedal one, hominins have shorter, broader iliac blades, wider, crescentshaped sacrums, and larger auricular surfaces. While the ape vertebral column has a single arch, hominins have dual-arched vertebral columns to allow an upright posture. These arches are called the lumbar lordosis and the thoracic lordosis. Brachiating apes have 4 lumbar and 6 sacral vertebrae to allow a more rigid lumbar spine. Hominins have 5 lumbar and 5 sacral vertebrae, which helps create the lumbar lordosis. Hominin pelvic limbs are elongated to allow efficient bipedalism, while ape pectoral limbs are elongated for brachiation. In hominins, the femoral head is larger and the neck-shaft angle of the femur is more obtuse than in quadupeds because the lower limb of bipeds must support much more weight. Hominin femurs also have a much more pronounced bicondylar
angle to bring the knees back underneath the body to support more weight. Bipedal tibias show a tibial plateau and ankle articulation with is perpendicular to the diaphysis, while these features in quadrupedal apes are angled. The ape pes is designed for grasping, so the hallux is set out at an angle and the metatarsals and pedal phalanges are longer and more curved. The hominin hallux is closer to the body and enlarged to support the weight of the entire body. Also, the hominin calcaneal tubercle is enlarged to allow full plantigrady. Hominins have a longitudinal arch, which acts as a shock absorber to allow more efficient bipedal locomotion.
Terms, Individuals and Concepts: lineage --------------------------------------------line of descent (ancestor-descendant relationships) hominoid -----------------------------------------superfamily including all extant apes, humans, and their ancestors hominin -------------------------------------------humans and their bipedal ancestors documentation/explanation --------------------documentation = noting facts, what happened? - good hypothesis testing, explanation = answering questions, why did it happen? - more complex homology -----------------------------------------similarity of STRUCTURE (in tissues, organs, skeletal elements, or genetics) that is traceable to a common ancestor C. Linnaeus -------------------------------------- Systema Naturae - developed system of taxonomic classification based on homology rather than function Homoplasy ---------------------------------------similar traits that emerge NOT due to common ancestry, but to parallelism - independent adaptations to similar ecological demands Y-5 (Dryopithecine) pattern -------------------lower molar cusp pattern of all hominoids sagittal crest -------------------------------------response to temporalis muscle, not under direct genetic control - homoplasy plesiomorph -------------------------------------ancestral features / ancient homologies apomorph ----------------------------------------derived features / recent homologies symplesiomporphy -----------------------------shared plesiomorph synapomorphy ----------------------------------shared apomorph W. Hennig ---------------------------------------German ornithologist, developed cladistics Proconsul ----------------------------------------E/M Miocene ape genera, 12-13 species, 17-55 kg - Africa (1st ape) Sivapithecus -------------------------------------M/L Miocene ape genera, 2-3 species, 75 kg - W Asia - India (1st in Asia) Dryopithecus ------------------------------------M/L Miocene ape genera, 15-45 kg - Europe (1st in Europe) Gigantopithecus ---------------------------------L Miocene - M Pleistocene ape genera, 225 kg - India-China (biggest) irreversibility of evolution ---------------------assumed by cladistics, organisms can never return to more primitive traits parsimony ----------------------------------------basis of cladistics - reconstruct relationships with fewest reversals & parallelisms possible sectorial premolar -------------------------------3rd mandibular premolar of apes - 1 cusp, hones canine nuchal plane -------------------------------------rough area of occipital bone where neck muscles attach, larger in apes temporonuchal crest ----------------------------crest across the back of some ape skulls - temporalis & nuchal muscles supraorbital torus -------------------------------bar of bone above eye orbits in some apes and fossil humans (brow ridge) simian shelf --------------------------------------bar of bone on inner surface of ape mandible, replaced by chin in humans maxillary diastema -----------------------------gap between canine & 2nd incisor to allow room for mandibular canine mandibular fossa --------------------------------area of temporal bone which articulates w/ the mandible full plantigrady ---------------------------------calcaneus strike form of plantigrade walking - only hominins (apomorph) intermembral index ----------------------------(humerus + radius) ÷ (femur + tibia) x 100, smaller in humans temporalis ---------------------------------------chewing muscle, extends to temporal line in humans, sagittal crest in apes
deep (anterior) gluteals ------------------------allows hominins to balace with 1 leg lifted - efficient bipedalism, on side stratocladistics ----------------------------------modified cladistics (P. Gingerich) - chronology, geography, possibility of reversals & parallelisms considered, Careful use of phonetic data T. Dobzhansky -----------------------------------Genetics and the Origin of Species - laid out STE G.G. Simpson ------------------------------------American Paleontologist - leading architect of paleontology’s role in STE quantum evolution ------------------------------Simpson’s model of macroevolution - change not gradual, but saltitorial with adaptive plateaus - species maintain status quo until a disruption S.J. Gould/N. Eldredge -------------------------presented punk-eek as theoretical alternative to STE species selection --------------------------------works on populations, not individuals (ex: mass extinctions) cladogenesis -------------------------------------speciation by branching anagenesis ---------------------------------------speciation without a specific branching event, Neandertals? modified quadrupedalism ----------------------knuckle walking in apes kyphosis ----------------------------------------- flexure of the cranial base, index higher in humans than apes prognathism -------------------------------------protruding jaw - apes orthognathism -----------------------------------flat jaw - Homo sapiens basicranium (cranial base)---------------------widest area of ape skull, changes more slowly than other parts of skull distal cutting blade -----------------------------sharp blade on rear of maxillary canine mandibular symphysis -------------------------connection of 2 halves of mandible pollex ---------------------------------------------thumb bicondylar angle---------------------------------angle of femur shaft relative to condyles (apes = 1-2%, humans = 7-11%) tibial plateau -------------------------------------proximal surface - perpendicular to shaft in humans, retroverted in apes vertebral lordosis -------------------------------curve in the spine, hominins have dual arch to allow bipedalism greater sciatic notch ----------------------------notch in os coxae in hominins, not apes gluteus maximus --------------------------------very important in hominins - allows powerful extension of the thigh for bipedal locomotion iliac flare -----------------------------------------lateral flare of ilium in hominins, not apes, due to anterior gluteals ischial tuberosity --------------------------------butt bone gluteal line ---------------------------------------attachment for gluteal muscles on ilium & femur of hominins anterior inferior iliac spine --------------------spine on the front bottom area of the ilium calcaneus -----------------------------------------heel bone pes -------------------------------------------------foot manus ---------------------------------------------hand hallux ---------------------------------------------big toe patellar groove ----------------------------------smooth area on distal surface of femur, articulates w/ the patella ilium, ischium, pubis ---------------------------3 bones that fuse to form the os coxa iliac pillar ----------------------------------------thicker area on human ilium, not in apes
5. Discuss cladisitics as a methodology for establishing phylogenetic relationships. How are polarities established? What are some limitations of cladistics? Include a discussion of stratophenetics. Cladistics - grouping on the basis of shared derived characteristics only (apomorphs) Four principles to judge polarity - whether a trait is plesiomorphic or apomorphic: 1. Last Common Ancestor (LCA) - most important principle 2. Outgroup comparison 3. Commonality 4. Ontogeny - general recapitulation principle (developed by Haeckel) - during development some primitive evolutionary traits may be present (Ex: gill slits and tails in human fetuses) Limitations: Developed for extant taxa - difficult to apply over time (biological history) Intermediates in fossil record difficult to handle (Ex: A. afarensis canine form) Parsimony - reconstruct relationships with fewest reversals & parallelisms possible = basis of cladistics Assumes the irreversibility of evolution & disregards functional shifts (change in adaptive conditions) Chronology irrelevant = biggest problem Stratocladistics = Modified Cladistics (Gingerich) Basis = cladistics (shared-derived traits) Chronology & geography taken into consideration Possibility of reversals & parallelisms considered Careful use of phenetic data 6. What is the synthetic theory of evolution? Out of what perspectives was it developed? What are its major tenants? Synthetic Theory of Evolution (STE) - brought together 2 perspectives: Genetic & Darwinian Mutation - the only creative evolutionary mechanism - only way to create new alleles Natural selection - primary mechanism of change Evolution - basis of genetic change - change in genes or gene frequencies Emphasis on populations as the unit of study - individuals do not evolve Macroevolution (origin of new species) = result of long-term microevolution (processes of change w/i a species 7. On what evidence did the punctuated equilibrium model challenge the STE? Provide an assessment of how effective this challenge is. In your opinion does it require replacing the STE? Why or why not? Punctuated Equilibrium Model of Macroevolution (“Punk-eek”), Five Points: 1. Evolutionary change is never constant and gradual, but always sporadic (saltational) - stasis is the rule, change is relatively rapid 2. Speciation always by branching (cladogenesis), never by anagenesis 3. Cladogenesis very common in biological history (Gould: “Evolution is a bush, not a ladder”) 4. Significant evolutionary change only occurs during speciation events - small peripheral populations opportunity for biological novelty 5. Evolution = hierarchical process w/ 3 levels - molecular, microevolutionary (population), & macroevolutionary (species) - different mechanisms at each level - macroevolution not an expansion of microevolution, directed by species selection - selection on populations, not individuals (ex: mass extinctions due to abrupt ecological changes - dinosaur extinction (K/T boundary - Cretaceous/ Tertiary) Because the Punctuated Equilibrium Model of Macroevolution includes arguments based on faulty assumptions, I do not believe that it offers a sufficient replacement for STE. Punk-eek claims that microevolution and macroevolution are driven by different selection mechanisms. While microevolution is driven by natural selection, macroevolution is supposedly driven by “species selection,” but this mechanism is merely an invented term for large-scale natural selection. Natural selection works on individuals, no matter the number. A species is not a discrete entity which can be acted upon, but rather a collection of individuals. Even in the case of mass extinctions, I do not believe that species selection occurs. In these cases, species become extinct because the individuals within
the species do not have enough variation to adapt to changing conditions. Therefore, this represents a large-scale version of natural selection. Also, punk-eek argues that speciation always occurs by cladogenesis, but I believe that anagenesis, though harder to definitively identify, is also possible. Quantum evolution accounts for saltation in the fossil record, the rarity of transitional fossils, and also the role of peripheral populations. 8. Using information from the skull and dentition, discuss the differences between extant ape and hominin anatomy. Where appropriate, discuss how these features are interrelated (e.g. all the features associated with the canine). Differences in Dentition: The maxillary canines of apes are large, projecting, and conical with a sharp apex and marked distal cutting blade. These teath wear from rear, which hones the canine. Because the canines are so large, apes have a distinct maxillary diastema, which allows the jaw to occlude. There is marked sexual dimorphism in the size of ape canines, with the male canine being much larger. Apes use these large canines for defense, display behaviors related to the competition for females, and food processing. Because the canine is such an important and predominant part of the ape dentition, many other features of the ape morphology are related to it. These features can be called the ape “canine complex.” Hominin canines are reduced in size and lack all these features. They are incisor-like and wear from tip. Since the canines are smaller, there is no maxillary diastema. Sexual dimorphism is much reduced. The third mandibular premolar of apes has a different shape than the fourth, so ape premolars are called heteromorphic. The ape P3 is sectorial, with one large mesially rotated cusp. This unique shape is an adaptation which helps hone the enlarged ape canine, so is part of the canine complex. The human P3 has two cusps, just like the P4, so the premolars are homomorphic. The first maxillary incisor in apes is larger than the other incisor and angled forward. This adaptation may relate back to the apes’ diet, helping them pluck fruit from the trees with their teeth. The first maxillary incisor in humans is similar to the other incisors. Also relating to their diet of fruits and soft vegetation, apes have a thin layer of enamel on the occlusal surface of their molars. Humans, due to dietary differences, have thicker enamel. Differences in Skull: Ape jaws are prognathic, so protrude much more than human jaws. The ape nasoalveolar clivus also angles out much more than that of a human. This prognathism relates back to the enlarged ape canine. Since the canine root is so large, the ape jaw must angle out to supply the necessary amount of space. The supraorbital torus in apes relates back to this prognathism, providing structural continuity of the face. Because the ape maxilla protrudes out, the mandible has a receding mandibular symphysis. All of these traits relate back to the ape canine complex. Since human jaws are orthognathic, humans have a more vertical mandibular symphysis and a higher cranial base flexure index. In humans, a mental eminence (chin) replaces the ape simian shelf. While ape skulls are widest at the level of the cranial base, human skulls reach their maximum width much higher, at the temporal line. Humans have a much larger cranial capacity due to their larger brains. The foramen magnum is located more posteriorly in apes, which relates back to the angle of the spine in quadrupedal locomotion. Humans have a well developed articular tubercle, which is lacking in apes. Since apes have stronger temporalis and nuchal muscles, and some individuals have temporonuchal and sagittal crests to provide additional muscle attachment area. Apes also have a much more expanded mastoid area and nuchal plane, which allows attachment for their strong neck muscles. 9. Discuss in general what we know about the Miocene radiation of great apes. Be sure to focus on the genera mentioned in class (particularly Proconsul, Sivapithecus, and Dryopithecus). What are the changes over time in both morphology and geographic spread? The Miocene Epoch (23-5 mya) was a time of great adaptive radiation of apes. 17-18 mya there was permanent land contact between Africa and Eurasia, which allowed extensive faunal exchange (apes to Eurasia, elephants to Africa). During the early Miocene the climate was warm and wet, with extensive tropical forests. These conditions were perfect for apes, and ~14 genera & ~50 species of apes are known from that time. Later, around 14 million years ago, the Miocene climate began to change drastically. The temperature and precipitation dropped, causing the lush forests to shrink and fragment. Because of this ecological change, apes were forced to move into new niches, particularly the expanding grasslands. This move required adaptations in both behavior and morphology. For example, Gigantopithecus and early Australopithecus show thicker molar occlusal enamel, which would have allowed them to eat tougher foods which were available in the grasslands. All Miocene apes share hominoid
apomorphies, such as the Y-5 molar pattern and the coccyx. They also show cranial, mandibular, dental, and postcranial characteristics that are similar to extant apes (except maybe Sahelanthropus & Orrorin). Miocene Ape Genera: 1. Proconsul: E/M Miocene (23-14 mya), 12-13 species, 17-55 kg - Africa - earliest ape form! Ape-like crania, mandible & dentition, BUT lacks extant ape postcranial apomorphs intermembral index = 87 → no pectoral limb elongation, manus lacks elongation & curvature of metacarpals & phalanges - palmigrady, Carpus (wrist): long styloid process of ulna All monkey-like features! (Primitive, monkey-like postcranium, but no tail) Thus - generalized arboreal quadruped like monkeys, NOT – brachiator 2. Afropithecus: E/M Miocene, 1 species, 50 kg - Africa 3. Sivapithecus: M/L Miocene (15-7 mya), 2-3 species, 75 kg - W Asia - India (earliest ape in Asia) • Narrow interorbital region, oval orbit shape, concave lateral facial profile, Pongo subnasal morphology • All of these features are apomorphic for hominids • Thus Sivapithecus & Pongo = synapomorphs, Sivapithecus → early Pongo lineage 4. Dryopithecus: M/L Miocene (14-7 mya), 15-45 kg - Europe (earliest ape found in Europe) • Crania, mandibles, dentition, & postcrania are ape-like • limb proportions, manus, carpus brachiator/modified quadruped 5. Ouranopithecus: L Miocene (10-9 mya), 100 kg - SE Europe (Turkey/Greece) 6. Lufengpithecus: L Miocene (9-8 mya), 50 kg - China 7. Gigantopithecus: L Miocene - M Pleistocene (9-0.3 mya), 225 kg - India-China • Poorly known (4 mandibles, teeth, few postcranials), Asian or African ape? • 2 species (G. blacki = M Pleistocene of China; G. giganteus = L Miocene of India) • Largest ape that ever lived (large male ~ 300 kg) • Found at Homo erectus sites in China – nature of interaction unknown • Strange, cupping wear on molars similar to Ailuropoda (giant panda) – specialized bamboo feeding, possibly outcompeted by pandas • distal humerus suggests modified quadruped – but no solid knowledge of postcranial adaptations 8. Sahelanthropus: L Miocene (7 mya) - Africa (1 skull) One of the earliest possible hominins - anterior foramen magnum, no postcranial evidence Temporonuchal crest, prognathic face, brow ridge Reduced canine, no diastema 9. Orrorin: L Miocene (6 mya) - Africa (fragmentary postcranial) - Also possible early hominin Proconsul, Dryopithecus, Afropithecus, Lufengpithecus, Ouranopithecus all exhibit extant African Great Ape patterns of: • Broad interorbital area, roundish orbits, straight lateral facial profile, & African subnasal morphology • These features are all plesiomorphic for hominids (great apes) – all these taxa share sympleiomorphs 10. Provide an assessment of how the human pelvis, lower limb, foot and vertebral column are modified for obligate bipedalism. The bones of the hominin pelvis are shaped differently than an ape pelvis to provide an attachment site for the muscles necessary to bipedal movement. For example, in hominins the gluteus maximus, which provides powerful thigh extension during bipedal locomotion, attaches to the post-acetabular region of the iliac blade. In apes, this muscle is much less important, so the post-acetabular region is much less extended. Since the bipedal pelvis has to support much more weight than a quadrupedal one, hominins have shorter, broader iliac blades, wider, crescentshaped sacrums, and larger auricular surfaces. While the ape vertebral column has a single arch, hominins have dual-arched vertebral columns to allow an upright posture. These arches are called the lumbar lordosis and the thoracic lordosis. Brachiating apes have 4 lumbar and 6 sacral vertebrae to allow a more rigid lumbar spine. Hominins have 5 lumbar and 5 sacral vertebrae, which helps create the lumbar lordosis. Hominin pelvic limbs are elongated to allow efficient bipedalism, while ape pectoral limbs are elongated for brachiation. In hominins, the femoral head is larger and the neck-shaft angle of the femur is more obtuse than in quadupeds because the lower limb of bipeds must support much more weight. Hominin femurs also have a much more pronounced bicondylar
angle to bring the knees back underneath the body to support more weight. Bipedal tibias show a tibial plateau and ankle articulation with is perpendicular to the diaphysis, while these features in quadrupedal apes are angled. The ape pes is designed for grasping, so the hallux is set out at an angle and the metatarsals and pedal phalanges are longer and more curved. The hominin hallux is closer to the body and enlarged to support the weight of the entire body. Also, the hominin calcaneal tubercle is enlarged to allow full plantigrady. Hominins have a longitudinal arch, which acts as a shock absorber to allow more efficient bipedal locomotion.
Terms, Individuals and Concepts: lineage --------------------------------------------line of descent (ancestor-descendant relationships) hominoid -----------------------------------------superfamily including all extant apes, humans, and their ancestors hominin -------------------------------------------humans and their bipedal ancestors documentation/explanation --------------------documentation = noting facts, what happened? - good hypothesis testing, explanation = answering questions, why did it happen? - more complex homology -----------------------------------------similarity of STRUCTURE (in tissues, organs, skeletal elements, or genetics) that is traceable to a common ancestor C. Linnaeus -------------------------------------- Systema Naturae - developed system of taxonomic classification based on homology rather than function Homoplasy ---------------------------------------similar traits that emerge NOT due to common ancestry, but to parallelism - independent adaptations to similar ecological demands Y-5 (Dryopithecine) pattern -------------------lower molar cusp pattern of all hominoids sagittal crest -------------------------------------response to temporalis muscle, not under direct genetic control - homoplasy plesiomorph -------------------------------------ancestral features / ancient homologies apomorph ----------------------------------------derived features / recent homologies symplesiomporphy -----------------------------shared plesiomorph synapomorphy ----------------------------------shared apomorph W. Hennig ---------------------------------------German ornithologist, developed cladistics Proconsul ----------------------------------------E/M Miocene ape genera, 12-13 species, 17-55 kg - Africa (1st ape) Sivapithecus -------------------------------------M/L Miocene ape genera, 2-3 species, 75 kg - W Asia - India (1st in Asia) Dryopithecus ------------------------------------M/L Miocene ape genera, 15-45 kg - Europe (1st in Europe) Gigantopithecus ---------------------------------L Miocene - M Pleistocene ape genera, 225 kg - India-China (biggest) irreversibility of evolution ---------------------assumed by cladistics, organisms can never return to more primitive traits parsimony ----------------------------------------basis of cladistics - reconstruct relationships with fewest reversals & parallelisms possible sectorial premolar -------------------------------3rd mandibular premolar of apes - 1 cusp, hones canine nuchal plane -------------------------------------rough area of occipital bone where neck muscles attach, larger in apes temporonuchal crest ----------------------------crest across the back of some ape skulls - temporalis & nuchal muscles supraorbital torus -------------------------------bar of bone above eye orbits in some apes and fossil humans (brow ridge) simian shelf --------------------------------------bar of bone on inner surface of ape mandible, replaced by chin in humans maxillary diastema -----------------------------gap between canine & 2nd incisor to allow room for mandibular canine mandibular fossa --------------------------------area of temporal bone which articulates w/ the mandible full plantigrady ---------------------------------calcaneus strike form of plantigrade walking - only hominins (apomorph) intermembral index ----------------------------(humerus + radius) ÷ (femur + tibia) x 100, smaller in humans temporalis ---------------------------------------chewing muscle, extends to temporal line in humans, sagittal crest in apes
deep (anterior) gluteals ------------------------allows hominins to balace with 1 leg lifted - efficient bipedalism, on side stratocladistics ----------------------------------modified cladistics (P. Gingerich) - chronology, geography, possibility of reversals & parallelisms considered, Careful use of phonetic data T. Dobzhansky -----------------------------------Genetics and the Origin of Species - laid out STE G.G. Simpson ------------------------------------American Paleontologist - leading architect of paleontology’s role in STE quantum evolution ------------------------------Simpson’s model of macroevolution - change not gradual, but saltitorial with adaptive plateaus - species maintain status quo until a disruption S.J. Gould/N. Eldredge -------------------------presented punk-eek as theoretical alternative to STE species selection --------------------------------works on populations, not individuals (ex: mass extinctions) cladogenesis -------------------------------------speciation by branching anagenesis ---------------------------------------speciation without a specific branching event, Neandertals? modified quadrupedalism ----------------------knuckle walking in apes kyphosis ----------------------------------------- flexure of the cranial base, index higher in humans than apes prognathism -------------------------------------protruding jaw - apes orthognathism -----------------------------------flat jaw - Homo sapiens basicranium (cranial base)---------------------widest area of ape skull, changes more slowly than other parts of skull distal cutting blade -----------------------------sharp blade on rear of maxillary canine mandibular symphysis -------------------------connection of 2 halves of mandible pollex ---------------------------------------------thumb bicondylar angle---------------------------------angle of femur shaft relative to condyles (apes = 1-2%, humans = 7-11%) tibial plateau -------------------------------------proximal surface - perpendicular to shaft in humans, retroverted in apes vertebral lordosis -------------------------------curve in the spine, hominins have dual arch to allow bipedalism greater sciatic notch ----------------------------notch in os coxae in hominins, not apes gluteus maximus --------------------------------very important in hominins - allows powerful extension of the thigh for bipedal locomotion iliac flare -----------------------------------------lateral flare of ilium in hominins, not apes, due to anterior gluteals ischial tuberosity --------------------------------butt bone gluteal line ---------------------------------------attachment for gluteal muscles on ilium & femur of hominins anterior inferior iliac spine --------------------spine on the front bottom area of the ilium calcaneus -----------------------------------------heel bone pes -------------------------------------------------foot manus ---------------------------------------------hand hallux ---------------------------------------------big toe patellar groove ----------------------------------smooth area on distal surface of femur, articulates w/ the patella ilium, ischium, pubis ---------------------------3 bones that fuse to form the os coxa iliac pillar ----------------------------------------thicker area on human ilium, not in apes
