humans as primates

what are considered apes?

humans, apes, monkeys and some other relates animals are called primates because they are all classified together in the taxinomic order primates

what is taxonomic order?

a place in a hierarchal system for classifying and organising living organisms bases on shared characteristics and evolutionary relationships.

why are non human primates of special interest to us?

because they re the closest living relatives to out own species. comparative study of primates is fundamental to any investigation of evolution of modern humans

what are some of the techniques/ things studies to try to understand how human characteristics evolved?

comparative anatomy, comparative biochemistry, including DNA and proteins, behaviour of living primates, fossils of primates

why is the classification of primates a dynamic process?

because as new information comes to light, classification of an organism may change

what is an example of classification process being a dynamic process?

the classification of Prosimians, they originally were included with prosimians (primitive primates) based on physical characteristics. but based on studies of protein sequences and DNA most scientists now classify Tarsiers as more closely relates to monkeys, apes, and humans

how are humans classified

in the same family as great apes, we have very similar DNA and many shared characteristics

it is common for the term ‘apes’ to refer to gorillas, orangutans and chimpanzees and not humans…

however as they are all in the same family, humans are also considered apes

what are some characteristics of apes?

there is no one characteristics that can be used to operate primates from all other mammals. However some features are started by all primates can be used to identify them as a group. and most of the features are a result of primates having evolved in arboreal or tree like environment. main features being combination of grasping fingers and toes and overlapping binocular vision.

what is the level of classification of primates e.g tarsiers, lemurs, lorises, money, apes, humans?

Order

what animals are included in Primates?

tarsiers, lemurs, lorisers, monkeys, apes, humans

what classification are the Haplorhini group e.g Tarsiers, monkeys, apes and humans?

Suborder

what animals are included in the Haporhini group?

Tarsiers, monkeys, apes and humans

what level of classification is Simiiformes, e.g monkeys apes and humans?

is the infaorder

what animals are included in the Simiiformes?

monkeys, apes and humans

what level of classification is the Catarrhini group e.g old world monkeys, apes and humans?

Paraorder

what animals are included in Catarrhini

old world monkeys, apes and humans

what level of classification is Hominoidea, apes and humans?

super family

what aminlas are inlcuided in Hominoidea

apes and humans

what level of classification is hominidae, all modern and extinct orangutangs, gorillas and chimps and humans?

family

what animals are included in hominidae?

all modern and extinct orangutangs, gorillas, chimps and humans

what level of classification is hominiae, all modesn and extinct chimps, gorillas and humans?

subfamily

what animals are included in hominiae?

all modern and extinct chimps, gorillas, and humans

what level of classification is hominini, extinct and ancestors of humans and modern humans?

tribe

what animals are included in the tribe hominini?

all extinct ancestors of humans and modern humans

what level of classification of Homo, some extinct ancestors of humans and modern humans?

Genus.

what animals are included inn the Genus Homo?

some extinct ancestors of humans and modern humans.

what level of classification is the sapiens, modern humans?

species

what animal is included in the species Sapiens?

modern humans

what is the primate characteristic of the body?

the body is not specialised for a particular environment.

what is the primate characteristic for the limbs?

that they are generally unspecialised

what is the primate characteristic of the hands and feet?

they are pentadactyl, mening that they have five fingers and toes of each limb, they gave nails instead of claws, have grasping fingers and toes friction ridges for gripping, they are first digit opposable

what does pentadactyl mean?

5 fingers and toes on each limb

what is the primate characteristic of the eyes?

they are forward facing for 3 dimensional (stereoscopic) vision and most are able to distinguish colour

what is the primate characteristic of sense of smell?

it is very poor

what is the primate characteristic of the teeth?

there is four incisors in both the upper and lower jaw.

what is the primate characteristic of the brain?

it is large and complex and the cerebrum six increases and primates become highly evolved.

what is the primate characteristic of reproduction?

there is no restricted breeding season, rhythmical sexual cycle, usually only one offspring at a time, a long parental care for offspring

what is the variation within the family homnidae?

humans are in the same family as great apes (orangutans, gorillas, chimps and bonobos) the homnidae family (the members are called hominids)

why are humans no longer the only ones classifies as a family?

advances in molecular techniques have shown that humans share a common ancestor with chimpanzees and gorillas (orangutans are slightly more distantly related with bonobos separating art a a more distant branch of the phylogenetic tree)

all species in the family homindae share some common characteristics. what are they?

larger and more complex brain than other primates (enabling a higher cognitive ability therefore can recognise themselves in a mirror) five cusps in the molar teeth of the lower jaw, arms that can freely rotate at the shoulder, a wide and shallow chest cavity, no external tail, an appendix, and being active during the day (Diurnal)

what is it called when a primate is active during the day?

diurnal

what are some of the variations that are present in the hominids that reflect the changes in DNA neuclotide sequences during evolution?

the relative size of the cerebral Cortex, mobility of the digits, locomotion- adaptions to bipedalism and quadropedalism, prognathism (protruding jaw) and mention (arrangement, number and types of teeth in the mouth)

Describe the differences in the mobility of digits within the hominids?

the limbs of primates tend to be unspecialised in structure, allowing great diversity in their use. they are pentadactyl, prehensile and have opposable thumbs.

what does it mean that the hominid digits are pentadactyl?

meaning that they have five digits on each limb, they are highly mobile (this can be related to the aboreal way of life of primitive ancestors)

what are prehensile digits?

grasping digits essential for climbing by wrapping the long, curved digits around the branches of trees

what are opposable thumbs?

this means that the thumb can cross the palm and touch each of the other digits (however humans are the exception from the primates where the feet do not have an opposable big toe like the other)

what is the evolutionary trend of the mobility of the digits?

the evolutionary trend is towards the increasingly ability to move the digits independently of one another. the most highly developed digits (in this respect) is the thumb and big toe

describe the degree of opposability of the digits.

it varies between species. almost all species of primates show some opposability with the big toe (humans are the exception, ours is not opposable at all).

what does the degree of opposability rely on?

the relative length of the first digit compared to the other 4

why was humans ability of big toe opposability lost?

it was lost due to the human foot becoming weight bearing, rather than a grasping appendage. being opposable is a disadvantage when weight bearing because it means uneven weight distribution and therefore poor stability.

describe the mobility of digits in hominids.

the humans posses the longest thumb, this is contributed with he ability to manipulate materials with our hands (more than other primates)

describe the human hand.

it is short, broad with shoer and straight fingers and a long, strong thumb compared with that of other primates

what does the structure of the human allow for?

the arrangement of the human hand allows a great degree of freedom and it is able to readily oppose other digits (thumb to fingertip) this allows humans to grasp with precison.

what is the prescision grip used for?

writing, sewing and construction

what is the power grip?

this is when the thumb and the fingers apply force to the palm.

is the presision grip uniquely human?

the precision grip is not uniquely human, but wheat is unique is the amount of contact between the index finger and the thumb. this enables humans to handle small and delicate objects effectively

what does the precision grip require?

it requires the presence of a truely opposable thumb. this is also seen in Old wold monkeys, particularly in ground living baboons, mandrills, macaques (these monkeys are second only to humans with their manipulative abilities)

why do most primates have nails instead of claws?

this is so that the tips of the digits are modified for better grip in the trees, nails allow for better grasping,

nails evolved from…

claws that became flattened.

what are some primates that still have claws?

Aye- Ayes and Lemurs

why do lemurs still have claws?

"the “toilet claw” is used for grooming and scratching

Why do Aye- Ayes still have claws?

they have extremely long claws for hookinh larva out of trees

what is the point if friction ridges or fingerprints on the fingertips?

it increases the grip

the digits have an increase of what kind of receptor and why?

the digits also have more sense receptors for feedback when gripping and manipulating

how can we see evolutionary changes in the dention of species/ fossils?

we can look at the dental formula, primitive mammals have the formula 3:1:4:3

What is the dental formula?

the formula goes the number of each type of tooth in one quarter of the jaw

explain the dental formula for primitive mammals?

3:1:4:3, three incisors, one canine, four premolars and 3 molars

how is natural selection linked to the dention of different species?

natural selection resulted in a decrease in the number of teeth in primates compared with early mammals. this is probably related to a gradual reduction in size of face and haw that allowed the skull to balance for bipedalism.

what is the dental formula for old world monkeys, apes and humans?

they have 32 teeth with a dental formula 2:1:2:3, two incisors, one canine, two premolars and three molars (however there is confidence difference between he structure and arrangement of teeth )

what is the evolutionary trend for new world monkeys and there dental formula?

they have an evolutionary trend for missing the third molar from the lower jaw. 2:1:3:3/ 1:1:3:3

what is the structure of teeth in old world monkeys and apes?

the canines are usually large and sharply pointed, projecting beyond the level of the upper teeth. these such large canines have required modification to adjacent teeth so that the mouth can be closed —> this creates a diastema.

what is a diastema?

most primates with large canines have a gap, or diastema between the upper second incisor and the upper canine to accommodate the lower canine. to allow for this upper canine the crown of the first lower premolar is slanted back and has a sharp edge. the upper canine fits tightly against this premolar and is sharpened by the grinding that occurs.

describe the evolution that has occurred on the surface of the molars of humans and apes?

the surface of molars of apes and humans evolved form 3 cusps of early mammals to four cusps on upper molars and 5 on the lower Ines. This pattern has been uselful in identifying the teeth of fossil apes and humans, it is presumed to have evolved due to predominatly fruit diet of apes

describe the dention of humans

compared to other primates human dentition is very distinct. in humans canine teeth do not project beyond the level of the other teeth and interlock, as they do in old world monkeys and apes. the canines are more even in size, looking more like incisors. the small canine rteeth and relatively small incisors take up less room in the jaw. therefore as consequence the shape of tooth row or dental arcade has evolved to a different shape. is parabolic not U

dental arcade in humans?

parabolic not U shaped like other primates

some adaptations in teeth are not because of changes to diet, what is another example for changes in dention.

the large canines in old world monkeys are not defence and social display.

what does a molar with 4 cusps look like?

the valleys form a + pattern

what does a molar with 5 cusps look like?

the valleys form a Y pattern

what is the evolutionary trend with vision?

as primates evolved, there is emphasis on vision

why is there an emphasis on vision as primates evolve?

due to the arboreal lifestyle in the trees, primates needed to be able to accurately judge jump and branch distance.

what happened to the other senses when there became an emphasis on vision?

there is a decreases emphasis in olfaction (smell)

what happens to as a result of an emphasis on vision?

there is a change in skull shape. because there is less use of the nose and snout to sense environments, there is a greater use of the eyes (e.g lemurs use snout to sense environments/ investigate objects vs apes who use their hands and eyes), the brain case larger, movements of eyes so that they face forward, neural connection between brain and eye improved, retina- rods and cones.

discuss what happened to vision when the eyes evolved to face forward.

it allowed for stereoscopic (3D) vision, accurate distance perception when leaping between branches, the field of view became narrower (this could be a disadvantage) e.g from predators- but this is compensated for by having a mobile head and neck therefore we can “look around”

our bony eye sockets…

protects our eyes

describe the retina, rods and cones in our eyes.

the rods are important for vision in limb light, and cones are for visual discrimination and colour vision.

how has the neural connections between the eyes an the brain evolved?

our acute vision (ability to see fine details has improved) and the coordination between our eyes has evolved.

what can we see happen to the skull when vision becomes prioritised in primates?

evolution in eye sockets and the brain regions have become larger for vision and smaller for olfaction in primates more closely related to humans.

what is the function of the cerebrum in primates?

the cerebrum is the part of the brain responsible for complex functioning. this progressively increasing in size with primates more closely related to humans (with primates with a closer common ancestor) concerned with vision, memory, reasoning, manipulating ability, construction and language (these are necessary for coping with changes to environment)

describe the evolutionary trend of cerebral cortex size.

this progressively increased in size. especially the oyster region called the cerebral cortex (the region concerned with so called higher functions)

primates have a large brain for…

body size

how is the large primate brain for body size concequence for tree dewilling environment?

the pressure of natural selection in arboreal environment would have been favoured more accurate visual and tactile preception and better coordination between sensory stimuli and any muscular response. vision produces a large amount of info that must be processed and stored, as unlike smell or hearing, reliance on vision wo move about and to locate and manipulate food generates a large amount of complex sensory information,

in primates what part of the brain carries out accurate visual and tacit epreception and better coordination between sensory stimuli and any muscular response and what is the effect of this part of the brain being more heavily relied upon?

the cerebral cortex, therefore there is a progressive expansion od the cerebral cortex has resukted in it become so large irt covers the rest of the brain (most noticeable in humans)

what is average brain size for humans?

around 900cm 3 up to 2200 cm 3 (an average of 1300cm3 in adulthood)

average brain size for apes?

between 400 to 500cm 3

what is the main reason of the huge difference in average brain size in apes and humans?

because of the cerebrum and epecially the cortex.

what part of the cerebrum’s the greatest increase in SA?

the frontal lobe, in humans it makes up 47% of total cortical surface and in apes it is 33% (it is the frontal lobe that the higher functions of thinking, reasoning and planning, processing takes place

brains of hominids have a strong pattern of…

convolutions

what does a large amount of convolutions enable?

it enables the SA of brains to increase, hence the cerebral cortex to be greatly increased, resulting in a 50% increase in surface area of the human brain compared to a brain of same size with no convolutions

what is the effect of an increased size of the cerebral cortex?

enables them to move about, locate food, develop specialised skills (tool making of humans and chimps), a greater variety of behavioural responses to meet a wide array of environmental problems (behavioural flexibility)