ANTH 270 Lab 5 Worksheet

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Anthropology

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Apr 3, 2024

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Anthropology 270 Lab 5: Bones and Behaviors Name: Diego Ryan Section Time: Thursday @ 4 Part 1: Introduction What can bones tell us about behavior? You have learned that the different primate groups have very unique cranial and dental features that allow anthropologists to tell them apart. In this lab we will expand on that, and explore how different primates also possess unique features (e.g., the lengths of the bones of the arms and legs) that reflect differences in locomotor strategy, differences in activity pattern (e.g. diurnal vs nocturnal), and differences in diet (e.g. folivorous, frugivorous, and insectivorous). Locomotion is defined as the act of moving from place to place, but also includes hanging and sitting postures. The 3 major locomotor strategies observed in primates are: vertical clinging and leaping, quadrupedalism, and suspension and brachiation .  Vertical clinging and leaping is defined by rapid leaping through the trees. Species who employ this locomotor strategy typically possess powerful hind limbs.  Quadrupedalism is the most common form of locomotion among primates and is likely a behavior that characterized the earliest mammals. There are both arboreal quadrupeds (in the trees) and terrestrial quadrupeds (on the ground).  Suspension and brachiation is made possible by relatively mobile shoulder and wrist joints, and also characterized by elongated fingers and short thumbs. Based on our anatomy, the human lineage evolved from a suspensory primate rather than a quadruped. Activity pattern is defined as the part of day (24-hour period) that a species is active. The 2 main activity patterns that we will explore are diurnal (day active) and nocturnal (night active) . There are other patterns, however. Species that are diurnal tend to have smaller cranial orbits relative to body/skull size. Species that are nocturnal tend to have larger orbits relative to the size of their skull. Last, there are many different dietary adaptations in primates. Dentition are a great skeletal element to analyze for understanding the diets of different taxa. The 3 main dietary categories we will explore are folivorous, frugivorous, and insectivorous .  Folivorous is one of the most common dietary categories in primates, and refers to leaf eating. Species that are highly folivorous tend to have high cusps with longer shearing crests on their molars and premolars. This is good for fracturing mechanically tough properties (e.g. leaf cellulose/fiber).  Frugivorous is also a common dietary category in primates, and refers to fruit eating. Species that are highly frugivorous tend to have low rounded cusps on their molars and premolars. This is good for grinding materials like fruit skin and pulps.  Insectivorous is the last category we will explore, and refers to insect eating. Species that are insectivorous tend to have very sharp cusps with steep crests for fracturing mechanically hard properties (e.g. insect exoskeletons). In-Class Lab Activity During lab today we will review primate features and explore how bones can be used to understand primate behavior (locomotion, activity pattern, and diet). You will have an 1

opportunity to handle specimens, see and measure features in person, and put your primate anatomy and behavior skills to the test during this lab, so please come prepared. Also, given the nature and ethics of handling sensitive casts and bones remains, there is no food or drink allowed in the lab room during this lab. Part 2. Evaluating Locomotion One of the major post-cranial differences among primates belonging to different locomotor strategies is the ratio between the lengths of the forelimbs (arms) and the hind limbs (legs). By comparing the length of the forelimb (e.g., humerus + radius) to that of the hind limb (e.g., femur + tibia), we can estimate a species' locomotor strategy. This ratio is known as the intermembral (IM) index and can be calculated using the following equation: length of humerus + length of radius length of femur + length of tibia X 100 = INTERMEMBRAL INDEX Generally, IM index scores much less than 100 (longer legs than arms) indicate vertical clinging and leaping, IM scores around 100 (equally long arms and legs) indicate quadrupedalism, and IM scores much greater than 100 (longer arms than legs) indicate suspension and brachiation. For this activity, you will explore how appendicular bones can be used to infer behavior by measuring bones to determining the locomotor strategy using the IM index. You will complete the table below (this same table is included in Question 1). Specie s Forelimb Hind limb IM Index Locomotor Strategy Humerus (mm) Radius (mm) Femur (mm) Tibia (mm) A 283 290 235 202 1.31 131.0 B 225 248 275 247 0.906 90.6 C 130 155 220 185 .704 70.37 Measure the forelimb and hind limb bones for Specimens A, B and C and then calculate each species' IM index using these data. Then, use the IM index to infer each species' locomotor strategy. Part 3. Evaluating Activity Pattern One of the major cranial differences among primates with different activity patterns is the ratio of the orbit diameter to the length of the skull. Rather than actually measuring these skulls, however, we want you do simply look at the orbit size and skull size, and make an estimation of their activity pattern using the information noted in part 1. Generally, diurnal primates will have smaller orbit sizes relative to the skull size (length), and nocturnal primates will have larger orbits relative to their skull size. 2

For this activity, you will explore how the skull and orbits can be used to infer activity pattern behaviors (diurnal or nocturnal). You will complete the table below (this same table is included in Question 2). Specie s Relative orbit size (small, intermediate, or large) Relative skull size (small, intermediate, or large) Activity Pattern A Intermediate intermediate Nocturnal B small large nocturnal C large small diurnal Part 4. Evaluating Diet and Dentition One of the major dental differences among primates with different diets is the sharpness of their molar cusps (peaks on the molars and premolars) and the degree of sheer on the molar crests (the amount of surface area for cutting found between the base of the crown and the cusp). Again, we will not actually be measuring this in labs, but we want you do simply look at the teeth (particularly the molars), and make an estimation of their activity pattern using the information noted in part 1 and the figures below. Generally, folivorous primates will have high cusps with long sheering crests, frugivorous primates will have low rounded cusps with shallow crests (and thus a low degree of sheer), and insectivorous primates will have sharp cusps with steep crests (and thus a low degree of sheer). Fruit (Frugivore) Leaves (Folivore) Insects (Insectivore) For this activity, you will explore how dentition can be used to infer diet. You will complete the table below (this same table is included in Question 3). Specie s Cusps (low, high, sharp) Crest sheer (low, high) Diet A sharp high insectvore 3

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