Chapter 6 (pp. 134-155) Biology in the Present: Other Primates
Overview Primatologists are: Scientists who study the evolution, anatomy, and behavior of nonhuman primates. Those who study behavior in free-ranging animals are usually trained as physical anthropologists. The three most famous are Jane Goodall (chimpanzees), Dian Fossey (mountain gorillas), and Biruté Galdikas (orangutans) -- all protégés of Louis Leakey (famous paleoanthropologist) The primates: There are approximately 230 species of nonhuman primates (lemurs, lorises, tarsiers, monkeys and apes). Each species has come to possess unique qualities for a particular habitat and lifestyle. Contemporary primates (including humans) aren t necessarily a representation of the final stage of a lineage. Living primates are not better than their evolutionary predecessors or other living species. Each possesses unique qualities that make it better suited to a particular habitat and lifestyle Let s start with a short, but profound observation: We are primates. Primates today are as evolved as we are. It is important, too, to recognize that our close resemblance to many primates is not a coincidence. Instead, we are so similar to them because we are related to them. We did not come from them; instead, we share a recent common ancestor with the other primates. More specifically, we share a very recent common ancestor with the African apes, a more distance ancestor with the monkeys, and an even more distant ancestor with the prosimians.
Primates are Mammals It is first necessary to understand the basic characteristics of these larger taxonomic groups Kingdom is the most inclusive taxonomic category. All living organisms can be places into one of five kingdoms: plants, animals, fungi, nucleated single-celled organisms, and bacteria. Humans belong to the animal kingdom. Humans belong to the phylum Chordata (animals with a spinal chord, called a notochord). Humans belong to the subphylum Vertebrata (the vertebrates, animals with backbones). One characteristic of vertebrates is bilateral symmetry -- left and right body sides are mirror images. Temperature regulation Modern mammals are homeotherms (capable of maintaining a constant body temperature under most circumstances). They are covered with fur or hair that insulates the body preventing heat loss in cold weather and reducing overheating in hot weather. Mammals also maintain a constant body temperature by ingesting large quantities of food, converting it to energy in the form of heat. Mammals are capable of exploiting a large number of environments. Humans have gone beyond basic temperature-regulating abilities through various technologies. Source: Wikicommons
What Is a Primate? 1 Humans are primates. But, what are primates? Primates are a group of closely related mammals that live in the tropics. 1. Primates are arboreally adapted mammals; that is, they possess many behaviors and anatomies that help them live a life in the trees. 2. Primates also display remarkable dietary plasticity, eating a wide variety of foods ranging from grasses and leaves, to other animals. 3. Finally, among the mammals, primates engage in the highest amount of parental investment, spending considerable time and energy in the few offspring that they have. Let s look in more detail at these characteristics and the adaptations that help primates survive. Skeletal structure Primates have a generalized skeletal structure, and have very mobile joints, They have mobile shoulders and elbows, and have quite dexterous hands and feet. These traits allow them to navigate through the trees, at times in acrobatic ways. Hands and feet with a high level of prehensibility (ability to grasp); not all primates have highly efficient opposable thumbs. An important primate character is the opposable thumb, which means that the thumb can touch the tips of the other fingers. This anatomy allows primates to grasp small objects, like thin branches, or insects. 1. With our long, robust thumb, humans have the greatest opposability, and this has allowed humans to possess both a power grip, like our ability to grasp and wield a hammer. 2. Also a precision grip, which allows us to pick up fine objects, like a coin. Another feature of primate hands is their expanded tactile pads (the ball of your thumb) and not claws
What Is a Primate? 2 Vision Nocturnal (night-active) primates are more likely to rely more on the sense of smell (olfactory sense) than diurnal (day-active) primates, which rely more on the sense of vision. Color vision is a characteristic of all diurnal primates. The nocturnal owl monkey only sees monochromatically. In between these extremes, color vision is variable. Depth perception (stereoscopic vision) allows primates to see 3-D. Several mechanisms help this to happen: Binocular vision (two eyes in front that have overlapping visual fields) Visual information is transmitted to both sides of the brain (60 opposite side of brain-40% on same side). 3-D images are produced by specialized structures in the brain. Decreased olfaction Compared to other mammals, primates tend to have reduced olfactory (smelling) abilities. Even within primates, the anthropoids (monkeys and apes) have further reduced their reliance on the sense of smell. Prosimian primates, like lemurs, retain a rhinarium (the wet nose that most mammals, like dogs, have). 1. Center your nose over the eye 2. Focus your eyes on the eye. 3. Put your free thumb in front of your nose. 4. Continue to focus on the eye. If both eyes are on, you will see two thumbs framing one eye. 5. Now, switch your focus to your thumb. You should see two eyes framing one thumb. Source: The framing game
What Is a Primate? 3 Teeth Many mammal species have evolved quite specialized teeth. Primates, however, have retained the primitive mouth Mammals have different types of teeth in their jaws. Teeth are generalized because primates are omnivorous. Lack of dietary specialization, means most are omnivorous. Terms: Omnivore (means all eating ); carnivores (including insectivores); herbivores (which include frugivores (fruit-eaters) and foliovores (leaf-eaters). We will spend some more time on teeth. The reason for this detailed look at teeth is twofold. 1. One way to describe the heterodont pattern of primates is by the dental formula. This is the number of each kind of teeth on the upper mouth (one side) with the number of each kind of teeth on the lower mouth (one side) They are heterodontic. Mammals have four different types of teeth: incisors (chisel-shaped front teeth for cutting, slicing, and gnawing), canines (teeth behind the incisors for puncturing and defense), premolars (back teeth used for crushing and grinding food), and molars (teeth furthest back, also for crushing and grinding). Dental formula is largely consistent with that of other mammals Not all primates have the human dental formula Notice the gap for the New World monkeys? That is called a diastema and is so the upper canine can fit in many primates).
What is a Primate? 4 Teeth (continued) 2. Teeth are some of the hardest objects in the body, and, therefore, they preserve very well in the fossil record. Much of what we know about fossil primates is from their preserved teeth. One way is to look at the shape of the tooth itself. Monkeys have four high ridges on their teeth two in the front and two in the back producing what is called a bilophodont pattern. But, apes do not. Apes have five low cusps that form a pattern that looks like the letter Y. This is called a Y-5 pattern and helps us identify ape teeth. Notice the Y-5 pattern drawn out on the (from left to right) gibbon, chimpanzee, and orangutan teeth. If you look in a mirror, you ll see the Y-5 pattern on your lower molars, as well. Additionally, while most monkeys and apes have flat, vertically oriented incisors, many prosimians have combined their lower incisors into a scraper-like structure called a tooth comb, shown here at the bottom. A tooth comb helps these little primates extract sap from tree bark.
What Is a Primate? 5 Parental investment Reproduction is central to evolution. And it is useful, in terms of behavior, to examine the costs and benefits associated with reproduction Life history theory deals with characteristics of an organism s life cycle and how they affect quantity and quality of reproduction. Age at reproduction, gestation length, interval between births, and overall life span are some considered characteristics. Energy allocation is a central concept of life history. Focus is on the tradeoff between energy needs of the number of offspring and their fitness. Some animal species have fast and slow life histories. Fast life histories are those where individuals reach maturity early and have large numbers of offspring. This is often called a r-selected species Slow life histories are those where maturity is delayed until later in the lifespan and the number of offspring is lower. This is often called a K-selected species Primates generally have slow life histories; are K-selected Basically this strategy requires: More efficient fetal nourishment; longer periods of gestation; reduced number of offspring; delayed maturation; extension of life span and less widely distributed to reduce loss of offspring in novel environments.
Classifying Primates 1 Primates, like all other animals, can be clustered into closely related nested hierarchies. These hierarchies are shown in this diagram: the primate family tree. By understanding the phylogeny (family-tree structure) of living primates today, researchers can determine which anatomies unite particular groups. This knowledge is important because if researchers find a fossil with a particular anatomy. Tarsiers are the problem. 1. The order primates can be split into two suborders, prosimians and anthropoids. Prosimians (lemurs, lorises and tarsiers) are often called lesser primates because they retain more primitive features than the more derived anthropoids (monkeys apes and us). Interestingly, there are some features, like the absence of a wet nose (rhinarium), that unite one group of prosimians (tarsiers) with the anthropoids. This taxonomy is primarily based on observable physical traits (a grade -based approach). 2. However, more recent approaches have emphasized not levels of anatomical complexity but ancestor descendent relationships, and find that tarsiers are more closely related to anthropoids than to prosimians. Under this evolutionary, or cladistic, scheme, tarsiers are united with anthropoids and collectively called haplorhines. Most researchers now subdivide primates into a group that includes the anthropoids and tarsiers, called haplorhines, while grouping all prosimians like lemurs and lorises (but not the tarsiers) as strepsirhines. DNA evidence supports this grouping, as well.. Within the hominoids are the hylobatids, or gibbons, the pongids (orangutans), and hominids (African apes and humans).
Two Taxonomies
Classifying Primates 2 Based on anatomical similarities and differences, researchers have historically grouped humans separately from the other apes. All of the great apes were thought to be closely related to one another in the pongid family, and humans had their own family: hominid. However, this all changed with the use of DNA as a tool for figuring out whether this traditional classification was, in fact, correct. It turns out that the great apes are not all equally related to one another. In fact, chimpanzees and bonobos are more closely related to humans than they are to the other apes. This new cladistic classification system reflects genetic similarity: All of the great apes, humans. together with gibbons compose the hominoid superfamily. Great apes and humans are in the hominid family. [In the old terminology, this was only for humans and their ancestors.] Groups humans and members of the genus Pan (chimpanzees and bonobos) together in the subfamily hominine. So, the word we use for just the human ancestors now is now the tribe hominin.
Two More Taxonomies