Primate Evolution

There are many differences between rodent and human skulls. These are mostly from the difference in shape and size to fit their lifestyles for them to survive. One example could be with the shape of the noses. In a rodent skull the whole nose is made up of mostly bone because they are longer due to the shape of their face. Whereas a human’s nose is made up of cartilage and the nasal bone because ours are smaller and not used in the same way theirs are. Theirs are used more for finding food in small spaces or smelling out danger, we don’t use ours to found food or smell for danger like rodents do. Another difference in the skulls is the size of their mouths. The nose bone for a rodent is also long because of the the teeth needed to eat.

Primates are one of the most interesting mammals on earth, not only because of their complex social structures, but because they hold so many similar characteristics to humans. Primates are often cited as our closest living relatives and on two separate occasions I observed four separate species of primates at the San Diego Zoo that can justify their use of their physical characteristics and behaviors that may be similar as well as different to the other primates and ours.

What makes a primate a primate? A primate is defined by its many incredible features. A primate is a mammal that has certain characteristics such as: flexible fingers and toes, opposable thumbs, flatter face than other mammals, eyes that face forward and spaced close together, large and complex cerebrum, and social animals. What makes a primate a primate is its characteristics. Some of the physical features primates are identified by is their teeth, snouts, eyes, ears, arms, legs, fingers, and toes. Human evolution is a big part of humans being primates, and having similar features and characteristics make humans to be considered to be a primate, but both humans and non-humans have differences.

Foreheads began to develop in the later members of the species, most likely as a result of an expanding frontal lobe (that part of the brain that we believe controls many of our higher functions such as reasoning, foresight and concentration) (Johanson and Shreeve 1989). Homo erectus had a lighter jaw than did Homo Habilis (Johanson and Shreeve 1989).

Within this essay, we will study more in depth the behavioral as well as physical traits of two primates at a zoo from their interaction with their peers to their place in the group. This observation would enable us to further understand the possible existing correlation between humans and primates. First, I studied a female chimpanzee with her baby, and then, a dominant male gorilla, in San Francisco Zoo at about noon, on May 23, 2015, for an hour each. Even though they share some similarities such as having a large brain, living for a long time, and being bored in their enclosure, they are still different; when gorillas are the largest, chimpanzees are the smartest. In fact, chimps use tools to catch food, they would not be able to reach

This paper aims to study the traits of non-human primates. By observing two types of primates including Common Squirrel Monkey (Saimiri sciureus) and Western Gorillas (Gorilla Gorillas), I try to find out their characteristics, pattern of their behavior, and differences between these two primate species. Especially, characteristics and behavior such as social interaction, food acquisition and intelligence will be discussed and compared in this paper. In order to enhance the persuasiveness of my observation, I recorded and examined at least 25 distinct characteristics of both Common Squirrel Monkeys and Western Gorillas. It is also helpful for me to compare these two primates. Apart from exploring the primates’ traits and differentiation between them, this paper will discuss the effects of captivity. How being in captivity and on display in a zoo would influence their behaviors and emotions? The observation was a great success and I have successfully derived with a hypothesis base on our observing data. The ultimate goal of this paper is arousing humans’ awareness of the importance of studying primates.

Non human primates’ social organization can provide useful information how human social evolution occurs. We will go over main points of how similar and different non human primates such as chimpanzees, orangutans, and gorillas’ society are compared to ours, humans.

Primates have some features that support them for the arboreal life. First, primates have developed grasping extremities with the divergent hallux and nails instead of claws. These features help them grasping branches better. Second, primates have enhanced vision with the optic convergence, which helps them look straightforward. They also have postorbital bar to protect the eyes. Third, primates reduced the olfaction that is not useful for arboreal life. Fourth, comparing to the other mammals, primates have large brain consider to the body size. The large brain helps them to process the complicating reactions, and thinking. Haplorrhines primates have some unique derived traits: the loss of tapetum lucidum, which enhances the vision in the darkness; and haplorhini, which is dry external nose. The anthropoid primates have developed some derived traits. They have postorbital bar with closure, and this makes a complete bony ring surrounds the eyes. They also have fused mandibular symphysis. The Platyrrhines have the dental formula 2.1.3.3/2.1.3.3. The Catarrhines have dental formula 2.1.2.3/2.1.2.3. The Cercopithecoids have the bilophodont molars to enhance the chewing ability. The hominoids are the most developed primates, which have some derived unique traits. They have larger brain, loss of tail, longer arms than legs, broad thorax with more muscles, and highly mobile shoulder.

The second grade of primates evolved about 53 million years ago, in Eocene epoch. There are five tarsier species that all live in the islands of Southeast Asia, where they inhabit from tropical forest to backyard gardens (Jurmain, et al, 2011). They are considered to be closely related to lemurs and lorises (prosimian family) for the several traits that they share with Grade I primates while having some anthropoid features as well. However, tarsiers have distinctive characteristics that isolate them from other primates. They are categorized as the smallest creatures among the primate species and they are well known for their enormous eyes which is as large as its brain. They are normally nocturnal insectivores but sometimes carnivorous. They catch insects by jumping at them and as they jump from tree to tree, they even hunt for birds while in motion.

The teeth of a gorilla have high crests that are used to help break down leaves that make up a large proportion of their diet. This species has relatively long forelimbs and short hindlimbs. The gorillas have a short trunk and wide pelvis. Individual gorillas can be distinguished from the nose; each gorilla has a unique nose pattern, like the human fingerprint.

The Strepsirrhini group are “more primitive than other primates such as monkeys and apes.” (3). Lemurs have olfactory communication, have stink and spur fights. Lorises are known for their “nocturnal behavior and are extremely slow in locomotion”. (3). Galago’s also called bush babies because their calls sound similar to an infant, they can jump about 8 feet from a sitting position and have very strong eyesight.

Kavanagh, M. & Morris, D. (1983). Complete guide to monkeys, apes and other primates. London: Viking Press.

According to Chimpanzee, an example of a homologous structure it shares with its descendants is its relatively large skull. As the animals became more evolved their skull shapes started to change to accommodate for a larger brain. This size difference is shown in Figure 2 because you can see the difference in the brain and skull size of the chimpanzees (bottom) and humans (top) (Chimpanzee). This is because Cranium size is determined by brain size and recent evidence by (Dumas, 2012) shows that this is likely determine by a protein domain called DUF1220. DUF1220 is a domain, a sub section of a gene, which is about 65 amino acids long and expressed mostly in neurons (DUF1220). Research (Dumas, 2012) shows that more copies present in the genome the larger the brain size is in that animal. Humans have 270 copies and the trend goes down from there with Chimps having 125, Gorillas 99 and marmosets 30 and mice just one (Dumas). This research shows the reasons hominids increased in brain size is because there was a mutation that increased the amount of DUF1220 in their lineage which led to gradually larger brain sizes. Since the Chimps split off (Figure 1) before this mutation their brains did not increase in size; hence the reason they are still similar to the common ancestor of both chimps and humans.

Western lowland gorillas (Gorilla gorilla gorilla) are part of the order Primates because they can be distinguished by their highly dexterous hands and feet (Schmidlin et al., 2011). They also have a higher-functioning brain region known as the neocortex, which is a characteristic seen in primates (Kaas, 2012). Additionally, they, like most primates, have a tendency to rely more on vision than their olfactory senses (Myers, 2000).

Addressing the various mating systems of primates and its relation to sexual size dimorphism and behavior contributes to understanding evolutionary processes and patterns. The different methods of mating are significant to study because they demonstrate the outcomes of natural selection on mate choice. These varying mating methods also aide in understanding the origin of