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- 6. Know an example (e.g., tamarins) Cercopithecines Colobines ATH 2100_Exam 2_Review Key Terms: Taxonomy Phylogeny Ancestral/Derived Traits Foraging Strategy Dental formula Heterodont Knuckle-walking Strepsirhine/Haplorhine Platyrrhine/Catarrhine Cercopithecoid Hominoid/Hominid/Hominin Adaptive Radiation Paleoanthropology Taphonomy Relative vs Chronometric dating Law of Superposition Homology Homoplasy Phylogram/Phylogenetic Tree Cladogram Parsimony Convergent Evolution Plesiadapiformes Ethogram Sampling methods Key Concepts: How is Linnean taxonomy organized? Where do primates fit into Linnean taxonomy? What are the ancestral traits that unite primates with other
- 7. mammals? What are the derived traits that unite primates compared to mammals? (Be specific!) What are the different types of primate diets? How does diet influence activity and foraging strategies? What are the different forms of locomotion found in primates? How is this reflected in their anatomies? What are characteristics of each major primate taxonomic group? (Strepsirhines, Haplorhines, Platyrrhines, Catarrhines, Hominoids, Cercopithecines, Colobines) What’s the deal with the tarsier? Pay attention to the social behavior of great apes. How are they different from other primates? Compare chimpanzee and bonobo behaviors. Why live in a group as a primate? What ways do they adapt to living in groups? Different mating/social systems (polygyny, polyandry, monogamy, solitary) When and why do we see sexual dimorphism? When don’t we see sexual dimorphism? How is human language different from non-human primate language? What have we learned from Great Ape language studies? What are some arguments to support culture in apes? Primate conservation Primates as models How do we get fossils? Methods of dating fossils What are the different methods of classification? What traits do each use? Be able to interpret a cladogram and phylogenetic tree. Major events in primate evolution by Epoch Hypotheses to explain the evolution of primates
- 8. ATH 2100L LAB 6: READING DIRECTIONS: Please read the materials that follow and then complete the Lab 6 Quiz on PILOT. By the time you finish reading these materials, you should be able to answer the following questions about primate taxonomy and anatomy: 1. What anatomical traits define each of the taxonomic groups within the Order Primates? 2. What are the different types of primate locomotion and their skeletal characteristics? 3. What is the intermembral index? The living primates: taxonomic classification Though you may not have known this before enrolling in ATH 2100, humans are primates. In fact, the Order Primates (pronounced Primate-ees) includes humans, apes, monkeys, tarsiers, and prosimians. You are mostly likely familiar with humans, apes, and monkeys but you probably have never heard of the group known as the prosimians. In the past (i.e., when I took this class in college), all primates belonged to one of two larger taxon: Prosimians or Anthropoids. Tarsiers along with lemurs, lorises, and galagos (now called Strepsirhines) were known as the Prosimians because they were nocturnal and generally small-bodied primates. Today we know that despite these similarities, tarsiers are more genetically similar to Haplorhines (previously known as the Anthropoids). Below is a table showing the old and new terms. Notice that the tarsiers move from Prosimian to Haplorhine: Old Classification New Classification PROSIMIAN
- 9. STREPSIRHINE lemurs, lorises, galagos, tarsiers lemurs, lorises, galagos ANTHROPOID HAPLORHINE apes, monkeys, humans tarsiers, apes, monkeys, humans The suborder Haplorhine comprises the majority of primate species alive today. Haplorhines can be further subdivided into Platyrrhines (aka New World Monkeys) and Catarrhines. The Catarrhines can be subdivided into Cercopithecoids (aka Old World Monkeys) and Hominoids. Cercopithecoids can further be broken into the Cercopithecines (aka cheek pouch monkeys) and Colobines (aka leaf eating monkeys), while hominoids include humans, greater apes, and lesser apes. Defining anatomical characteristics Below is a list of the defining characteristics of each primate group noted above. Where appropriate, cranial features are highlighted in blue. ALL PRIMATES: There are many defining characteristics of primates. From a cranial perspective, the strongest defining features are more forward facing eyes and the presence of a post-orbital bar. The post-orbital bar is a rim of bone on the outside of the eye socket (and can be seen in some other animals). In Haplorhines, this bar is also attached to a plate of bone behind the eye. We call this post-orbital closure. Please check out the image to the right or here: http://animaldiversity.ummz.umich.edu/collections/contributors/ anatomical_images/family_pages/primates/primates//medium.jp g
- 10. STREPSIRHINE (Lemurs, lorises, galagos): Defined by the presence of a moist rhinarium (for smelling scents, kind of like a dog), adental comb (for grooming; see image below), and a long toilet or grooming claw (also for grooming). Unlike most other primate groups, strepsirhines are heavily reliant on their sense of smell. Therefore, most strepsirhines also have a long snout to accommodate olfactory nerves. For a larger image, visit: http://upload.wikimedia.org/wikipedia/commons/thumb/4/45/Le mur_catta_toothcomb.jpg/220px-Lemur_catta_toothcomb.jpg HAPLORHINE (Tarsiers, apes, monkeys, humans): defined by the presence of a dry rhinarium (because vision is more important than smell) as well as the absence of a dental comb and the absence of a toilet claw.
- 11. TARSIERS: despite some similarities between tarsiers and the Strepsirhines, the defining difference between tarsiers and all other groups is the presence of a structure called the lateral genticulate nucleus in their brains. This structure contributes to a tarsier’s heightened sense of vision as they search for food in the dark. No tarsier skulls will be explored in this lab. PLATYRRHINES (New World monkeys): the name of these monkeys reveals much about their facial characteristics. “Platy” means “flat” and “rhine” refers to the nose (like rhinarium). As such these monkeys are defined by their broad, flat noses and outward facing nostrils (i.e. wide septum). These monkeys are also defined by the presence of a prehensile (grasping) tail and 2:1:3:3 dental formula. CATARRHINES (Old World monkeys and apes): this group, which includes the cercopithecoids and hominoids, is defined by downward facing nostrils, the presence of a narrow septum, and a 2:1:2:3 dental formula. (a) (b) A comparison of the dental formulae and nasal septums of (a) Catarrhines and (b) Platyrrhines. CERCOPITHECOIDS (Old World monkeys): these monkeys also have tails, like New World monkeys but they are not designed for grasping and instead help these monkeys with
- 12. balance. Dentally, the Old World monkeys exhibit a unique molar pattern called bilophodont molars. Note in the image to the right how there appears to be a line dividing the tooth into two halves (one on top, one on bottom). Each of those halves then has two cusps each (four cusps total). In general, bilophodont molars are symmetrically shaped and are useful for grinding foods. HOMINOIDS: this last taxonomic grouping includes all apes and humans. Unlike the monkeys, tarsiers, and strepsirhines (who all have tails), hominoids are tail-less. Dentally, the hominoids exhibit a unique mandibular (lower jaw) pattern called the Y-5 pattern. As illustrated in the image to the right, these lower jaw molars have five (not four) cusps, which are arranged in a “Y-shape.”
- 13. Locomotor patterns Compared to other mammalian groups, primates have a number of different locomotor patterns (i.e., ways of getting around). When only skeletal elements remain, it is useful to calculate the intermembral index to learn more about a particular “mystery primate’s” potential locomotive patterns. The intermembral index is simply the proportion of arm to leg length. Below is a list of the locomotor patterns (and their associated skeletal characteristics) used by different primates today as well as links to videos showing these different types of locomotion. QUADRUPEDALISM: All primates except humans walk on all fours (i.e., quadrupedally). There are variations on this type of walking, some of which are highlighted below: a) Arboreal quadrupedalism: This is a common type of locomotion that involves movement on top of tree branches. Arboreal quadrupeds tend to have short limbs that are equal in length, long tails for balance, and a low center of gravity. b) Terrestrial quadrupedalism: This type of locomotion occurs on the ground. Terrestrial quadrupeds have long limbs (to increase stride length) and some species even have shortened tails. i)Knuckle-walking: This is a form of terrestrial quadrupedalism found among gorillas and chimps which involves walking on the tips of the knuckles. Their long, curved fingers are adaptations for gripping branches, but they also move on the ground so they have to tuck in their fingers! If you look closely in this video, you can see knuckle-walking in action: http://www.youtube.com/watch?v=2Npc5QlS6Iw
- 14. d) Vertical clinging and leaping (VCL): This type of locomotion is used by tarsiers and some strepsirhines and haplorhines (New World monkeys). Usually VCLs have very long legs (for propulsion) and shorter arms. Some VCLs like tarsiers have elongated tarsal (ankle) bones. A VCL primate crouches with a bent leg and leaps from one tree to the next. http://www.youtube.com/watch?v=eGZdBi_dT-s e)Suspensory/Brachiation: This type of locomotion uses the arms to support the entire body below a tree branch. Suspensory primates usually have very long arms, short legs, and long, curved fingers to aid in gripping. http://www.youtube.com/watch?v=H3Wk33FZiVw BIPEDALISM: Humans always walk on two legs and some primates (especially chimps and bonobos) will occasionally walk bipedally, as needed. Human bipedalism is called habitual bipedalism while the occasional bipedalism of other primates is called facultative bipedalism. Here’s a brief summary of the key skeletal characteristics for each locomotion type. LOCOMOTION TYPE FORELIMBS (ARMS) HINDLIMBS
- 15. (LEGS) TAIL OTHER ARBOREAL QUADRUPEDALISM Short Short Length: Long, often prehensile (NWM); used for balance Curved phlanges TERRESTRIAL QUADRUPEDALISM Long Long Length: Variable (some no tail); not useful for balance Walk on fingers (digitigrade) or palms (palmigrade) VCL Short Long Length: Variable Tarsier: elongated tarsal bones SUSPENSORY/BRACHIATION Long Short Length: Variable (some no tail) Curved phlanges BIPEDALISM Short Long N/A N/A (for now!) Please note, you are not required to bring a copy of this reading to lab, but you are encouraged to do so in case you need to reference the materials as you answer lab questions. If you want to avoid large stacks of paper and the cost of printing, consider arranging a rotation among lab group members for printing and
- 16. bringing copies to each lab. ATH2100L LAB 5: READING DIRECTIONS: Please read the materials that follow and then complete the Lab 5 Quiz on PILOT. By the time you finish reading these materials, you should be able to answer the following questions about primates: 1. What ancestral traits do primates share with other mammals? 2. What derived traits characterize primates compared to other mammals? 3. What is the value of studying primates to understand human evolution? Primates are mammals (and therefore, so are you!) Taxonomic classification organizes organisms based on shared characteristics due to common ancestry. The Linnean classification system is a nested hierarchy that becomes more exclusive with each taxonomic level (for example, a phylum contains more groups than a class and so on). Below is the taxonomic classification for modern humans. Linnean Classification of Human GENERAL KINGDOMAnimalia (we’re ANIMALS) (inclusive) PHYLUMChordata (we’re animals with SPINAL CORDS) CLASSMammalia (we’re a kind of spined animal MAMMALS) ORDERPrimates (we’re a type of mammal called a PRIMATE) FAMILY Hominidae (includes us and apes, aka HOMINIDS)
- 17. GENUS Homo (this is us and closely related enchephalized bipeds) SPECIFIC (exclusive) SPECIES Homo sapiens(we’re a special group called HUMANS) From this classification, we see that modern humans are grouped within the order Primates which falls within the class Mammalia. This means that humans are primates, a special type of mammal that shares a common ancestry with OTHER mammals. As a result of this ancestry, primates and mammals share many ANCESTRAL TRAITS. Mammals are diverse. On the surface, it may seem hard to find similarities between humans and a dog or cat, etc. However, we all share traits found in our common mammalian ancestor that indicate a closer evolutionary relationship among all animals grouped within the Class Mammalia than other animals. Mammalian characteristics 1. Homeothermy/endothermy: Mammals have the ability to regulate body temperature. This means mammals can adapt to different climates. 2. Heterodonty: Mammals have different types of teeth. Mammals have four kinds of teeth with different shapes and characteristics: incisors, canines, premolars, and molars. Other animals, such as crocodiles and sharks are homodonts (the teeth are all the same). 3. Viviparity: Mammals have internal gestation and give birth
- 18. to live young (there are a few exceptions). Young are then dependent upon the mother for milk produced by mammary glands. 4. Pentadactyly: Mammals have five fingers and toes. The basic structure of the mammalian “hand” and “foot” is similar, but many groups have modified this condition (i.e. ungulates have hooves, felids have paws with claws). Primates retain the primitive structure of pentadactyly. 5. Brain: The mammalian brain tends to be larger for body size compared to other vertebrates. Mammals also have a unique area of the brain known as the neocortex. The neocortex is involved in higher level functions such as spatial reasoning and sensory perception. This area reaches its greatest expansion among primates. What makes primates different from other mammals? Primates are defined by a group of features, known as DERIVED TRAITS. Derived traits are modified from the ancestral (in this case, mammalian) condition. The tricky thing about ancestral and derived traits is that their status (or polarity) depends on the context. For example, if we are comparing mammals and primates, the features below are considered DERIVED. However, if we are comparing different groups of primates, those same features are considered ANCESTRAL because all primates share them. In the next lab, you will explore more in-depth what distinguishes primates from other mammals. Here are a few key features of primates: 1. Vision: Vision is the most important sense for most
- 19. primates. They have forward-facing eyes and stereoscopic vision. This means that a primate’s eyes are located in the front of the skull. This allows the fields of vision to overlap, and provides depth perception (very important if you primarily live in the trees). Furthermore, the primate eye socket features post- orbital closureor a post-orbital bar. You will explore this characteristic more in Lab 6. 2. Hands, feet, and limbs: Primates retain the ancestral condition of pentadactyly. They also have prehensile (gripping) fingers and toes, nails instead of claws (with some exceptions), tactile pads, and an opposable thumb. Primates also have very flexible and generalized limbs that allow us to locomote (move) in many different ways. 3. Brains and speed of growth: As mentioned above, primate brains are more complex than other mammals, and our brains tend to be larger than expected for body size (this is seen to the extreme among hominins). Primates also feature longer gestation periods and slowerpostnatal growth than most other mammals. The utility of non-primates for understanding evolution Non-human primates (NHP) are fascinating because they are so like us in both appearance and behavior (and many are very cute!) NHP studies help us to understand: a) the relationship between dental and skeletal form and their behavioral functions (to reconstruct things like locomotion, group structure, and diet in fossil species), b) the evolutionary underpinnings of some of our behaviors (tool use, group living, social politics, etc.) c) evolutionary processes, adaptation, and speciation. HOWEVER, we have to remember that extant NHP are not
- 20. “living fossils,” and they were evolving and changing long before hominins (our ancestors) ever came on the scene. Therefore, we must be cautious in our use of NHP as analogies for hominin evolution.