What are Primates
Primates are one of 20+ orders belonging to the class Mammalia, and probably one of the oldest. Genetic estimates put the origin of primates at around 91 million years ago.
Today the Order Primates is a diverse group that includes lemurs and lorises, tarsiers, monkeys, apes, and humans.
Why are nonhuman primates important
Nonhuman primates’ close relationship to humans makes them ideal for studying humans via homology, looking at shared traits between taxa inherited from a common ancestor.
Nonhuman primates also make excellent comparators for learning about humans via analogy. Many primates live in environments similar to those in which our ancestors lived and therefore exhibit traits similar to what we seen in humans. For example Humans and Baboons likely evolved long legs for the same reason, moving more efficiently over long distances in the savanna.
What are Clades and Grades
A clade is a grouping of organisms based on relatedness that reflects a branch of the evolutionary tree.
For example the African clade of hominoids contains humans, chimpanzees, bonobos, and gorillas, which all share the same branch of the evolutionary tree. Excluded from this group is the Orangutan which is a member of the Asian Clade of hominoids.
Grades are groupings that reflect levels of adaptation or overall similarity and not necessarily evolutionary relationships. For example, a grade might included gorilla,s orangutans, bonobos, and chimpanzees into a group while excluding humans due to differences in morphology, behaviour, and ecology.
What are Ancestral and derived traits
Ancestral traits are those that a taxon has because it inherited the trait from a distant ancestor. For example body hair in primates being inherited from an ancestor millions of years ago that had body hair.
Derived traits are those that have been more recently altered. Useful when trying to distinguish one group from another because derived traits tell use which taxa are more closely related to each other. For example, humans walk on two legs, an adaptation we gained since splitting from the lineage of the genus Pan.
The terms ancestral and derived are relative terms, and depend on which taxa are being compared. Ex body hair is ancestral when comparing primates, but derived when comparing mammals to reptiles.
What are Generalized and specialized traits
Generalized traits are useful for a wide range of things. Having opposable thumbs is one example.
Specialized traits are those that have been modified for a specific purpose. Hooves are a good example.
How are primates distinguished
The order primates is distinguished from other mammals by having a suite of characteristics. Meaning there is no individual trait that identifies a primate, you must look for animals that posses a collection of traits.
How is primate vision
Our order relies on vision as a primary sense, which is reflected with forward facing eyes with convergent visual fields. All primates have at least a postorbital bar, though many have a postorbital plate or postorbital closure.
Primates have trichromatic vision (can distinguish reds and yellows, blues and greens). While birds, fish, and reptiles are tetrachromatic (they can see reds, yellows, blues, greens, and even UV). Most mammals are only dichromatic (blues and greens). It is thought that ancestors of mammals benefited from seeing better at night rather than in colour, so dichromacy is ancestral for all mammals. Trichromatic primates use their colour vision for all sorts of purposes: finding young leaves and ripe fruits, identifying other species, and evaluating signals of health and fertility.
How are other primate senses
Primates have cut back on other senses, particularly smell. Primates have reduced snouts. There is variation, but primates with better senses of smell tend to have poorer vision.
The reason for this is that all organisms have limited amount of energy to spend on running our bodies, so we make evolutionary trade-offs, as energy spent on one trait cuts back on energy spent on another.
What are primate brains like
Primates also differ from other mammals in the size and complexity of our brains. On average, primate brains are twice as big as similar sized mammals. The visual centres of the brain are larger in primates, and the wiring is different reflecting our reliance on this sense.
The neocortex, used for higher functions like consciousness and language in humans, as well as sensory perception and spatial awareness, is also larger in primates relative to other animals.
What are two hypotheses for why primate brains are big
It has been proposed that the more complex neocortex of primates is related to diet, with fruit-eating primates having larger relative brain sizes than leaf-eating primates, due to the more challenging cognitive demands required to find and process fruits.
An alternative hypothesis argues that larger brain size is necessary for navigating the complexities of primate social life, with larger brains occurring in species who live in bigger, more complex groups.
There seems to be evidence for both hypotheses.
Describe Life History of primates
Life history refers to the pace at which an organism grows, reproduces, and ages. Primates are in the slow land of life history patterns. Primates develop slower, have fewer offspring per pregnancy, reproduce less often, and live longer. They also invest heavily in each offspring.
With a few exceptions, most primates give birth to one offspring at a time. A group of small monkeys in South America give birth to twins regularly, and some lemurs can give birth to multiple offspring at a time.
Primates also reproduce relatively infrequently. The fastest reproduce every 6 months, while the slowest (the orangutan) reproduces every 7-9 years, making them the slowest-reproducing animal on the plant.
The group including large bodied apes has the most extended life history patterns among primates, with some living up to 58 years in the wild.
How are primate ands adapted
Primates have the generalized trait of pentadactyly - possessing 5 digits on each limb. Many other mammals have fever digits because they are specialized for high-speed, terrestrial running. Pentadactyly is an ancestral trait dating back to the earliest tetrapods.
Primates today have opposable thumbs, and with the exception of humans, opposable big toes. This is a derived trait that appeared 55 million years ago.
Our ability to manipulate objects is enhanced by the flattened nails on the back of our fingers and toes.
One the other side of our digits, we have a sensitive tactile pad that allows us to have a fine sense of touch.
Are primates social
Lastly, primates are very social animals. All primates establish strong social networks within species. Primates do not migrate and form long term relationships with each other.
Summarize Primate traits
Summary of traits:
- Convergent Eyes
- Postorbital bar
- Many have trichromatic colour vision
- Short snouts
- Opposable thumbs and big toes
- Pentadactyly
- Flattened nails
- Tactile pads
- Highly arboreal
- Large brains
- Extended life histories
- Live in the tropics
What are primate teeth
Primates are heterodont: they have multiple types of teeth used for different purposes. We have incisors for slicing; premolar and molars for grinding up food; and canines (often used as weapons against predators and each other)
What is a diastema
The size of canines vary across species and can often be sexually dimorphic, with males tending to have larger teeth. Some non human primates hone, or sharpen their canines by gnashing the teeth together to sharpen the sides. The upper canine sharpens on the first lower premolar, and the lower canine sharpens on the front of the upper canine. As canines get larger they require a space to fit in order for the jaws to close. This space is called a diastema.
What is a dental formula
We use a dental formula to specify how many of each tooth are in each quadrant of the mouth. This is written as Incisors:Canines:Premolars:Molars. for humans this is 2:1:2:3
Incisors look like spatulas with a flat, blade-like surface.
Premolars are smaller and have one of two cusps on them.
Molars are bigger and have three to five cusps.
Canines are longer and more conical than the other teeth in most taxa.
The most common dietary types within primates are frugivores, insectivores, folivores (leaf eaters) and gummivores (eat gums and saps)
What are frugivores
Plants want animals to eat fruit so they can spread their seeds out. Plants often advertise fruits by making them colourful and easy to spot, full of easy to digest sugars, make them taste good, and often easy to chew and digest.
For this reason frugivores do not need a lot of specialized traits. Their molars have a broad chewing surface with low rounded cusps (referred to as bunodont molars). They have large incisors for slicing through the outer coatings of fruit, and tend to have stomachs, colons, and small intestines, that are intermediate in terms of size and complexity between insectivores and folivores. They are also usually intermediate in body size.
Frugivores who get protein from eating seeds evolved to have thicker enamel on their teeth.
What are Insectivores
Insects are easy to chew and digest. So insectivorous primates usually have small molars with pointed cusps to puncture the exoskeleton of the insects. They have simple stomachs and colons with long small intestine to process the insects. Nutritionally, insects provide a lot of protein and fat, but are not plentiful enough in the environment to support large-bodied animals, so insectivores are usually the smallest of the primates.
What are Folivores
Plants use leaves to get energy, and so don’t want animals to eat leaves. As a result, leaves often carry toxins, taste bitter, are very fibrous and difficult to chew, and are made of large cellulose molecules that are difficult of break down into usable sugars.
Folivorous primates have broad molars with high, sharp cusps conencted by shearing crests. These molar traits allow folivores to physically break down fibrous leaves when chewing. Folivores then chemically break down cellulose molecules into usable energy. They have complex stomachs with multiple compartments, while others have large, long intestines, and special gut bacteria that can break up cellulose.
Folivores are often the biggest of all primates, and spend a large portion of their day digesting their food, so they are less active than frugivores or insectivores.
How do primate move
Primate groups vary in their adaptations for different forms of locomotion.
Living primates are known to move by vertical clinging and leaping, quadrupedalism, brachiation, and bipedialism
Describe Vertical clinging and leaping
Vertical clinging and leaping is when an animal grasps a vertical branch with its body upright, pushes off with long hind legs, and then lands on another vertical support branch. Animals who move like this usually have longer legs than arms, long fingers and toes and smaller bodies. They also tend to have elongated ankle bones, which serve as a lever to help push off with their legs and leap to another branch.
describe Quadrupedialis
Quadrupedialis, waling on all fours is the most common form of locomotion among primates. Quadrupedal animals usually have legs and arms about the same size and a tail for balance. Arboreal quadrupeds usually have shorter arms and legs and longer tails, while terrestrial quadrupeds have longer arms and legs and often, shorter tails. These differences relate to the lower center of gravity needed by arboreal quadrupeds for balance in trees and the longer tail required for better balance when moving along the tops of branches.
Describe Brachiation
Brachiation is essentially monkey bars movement. It involves swinging below branches by the hands. To be an efficient brachiator, primates need to have longer arms than legs, flexible shoulders and wrists, a short lower back, and no trail.
Some primates move via semi-brachiation, in which they swing below branches but do not have all the same specializations as brachiators. They often have flexible shoulders, but their arms and legs are about the same length, which is useful to be quadrupedal on the ground.
They also use long prehensile tails as a third limb when swinging. The underside of the tail has a tactile pad, resembling your fingerprints for better grip.
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1b - Evolution of Evolutionary Theory31
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2a - Intro to genetics15
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2b - Ancient DNA13
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3a - Biology of Variation25
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3b - Mechanisms of Evolution18
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4a - Primates30
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4b - Primate Behaviour and Ecology28
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5a - Primate Evolution29
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Ch859
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Ch726
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Ch 60
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Ch 547
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Hominin Origins15
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Earliest Hominins19
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Mid-Late Pleistocene Hominins I: Eurasia16
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Mid-Late Pleistocene Hominins II: Asia and Africa13
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Modern Humans: Origins, Dispersals, and adaptation20
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Modern Humans 2: Origins, dispersals, and adaptations23
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Modern Human Variation14
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Understanding Human variability: Dismantling the concept of race22
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Climate and Human evolution20
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The influences of health and disease on contemporary humans22
