Primate evolution Flashcards
What is binomial nomenclature?
Uses generic (genus) and specific (species) names for the scientific name of a species
Categories list:
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
How are living organisms classified?
According to their structural features
Homosapiens
genus = homo species = sapien
Organisms that produce fertile offspring
Must be from the same species
What does being in the same species presume?
That you are in the same genus
Sub-groups in the classification system
- Kingdom
- Phylum
o Sub-phylum - Class
- Order
o Sub-order
o Infra-order
o Parv-order
o Super-family - Family
o Sub-family
o Tribe - Genus
- Species
o Sub-species
Types of primates
- Humans
- Apes
- Monkeys
- Tarsiers
- Lorises
- Lemurs
- Have some physical characteristics and DNA nucleotide sequences in common
What happens as you move down the hierarchy?
- Organisms in each group have more and more characteristics in common
- Start to have very similar DNA sequences
Classification of humans
- Classified into the family: hominidae
- Share this family with the great apes (e.g. Gorillas, Chimps and Orang-utans)
- Sub-family: homininae and share this subfamily with Chimpanzees and extinct humans
- Tribe: Hominini and share this tribe with the extinct humans
Binomial name for Orang-utans
Ponginae
Binomial name for Gorillas
Gorillini
Binomial name for Chimpanzee
Panini
Examples of lower primates
Non-tarsiers - Leumurs
Prosimians
Primate groups
Lower primates
Tarsiers
Higher primates
Examples of higher primates
New worldmonkeys - spider monkeys
Old world monkeys - baboons
Lesser apes - gibbons
Great apes - orang-utans, gorillas and chimpanzees
Humans - modern and extinct humans
Classification of primates
Kingdom = animal Phylum = chlordate Subphylum = vertebrate Class = mammal Order = primate
Characteristics of primates (15)
- Unspecialised body
- Unspecialised limbs
- Pentadactyl (5 limbs)
- Nails instead of claws
- Grasping digits with friction ridges
- Opposable first digit
- Forward facing eyes (stereoscopic vision)
- Colour vision
- Reduced sense of smell
- 4 incisors in top and bottom jaws
- Relatively large and complex brain
- Larger cerebrum in more complex primates
- Can reproduce throughout the year
- Rhythmical sexual cycle
- Usually one offspring at a time
- Long period of parental care
Strepsirrhini
Lemurs and Lorises
Tarsiformes
Tarsiers
Platyrrhini
New world monkeys
Cercopithecoidea
Old world monkeys
Hylobatidae
Simangs and gibbons
Pongids
Orang-utans
Panini
Chimpanzees
Hominini
Humans
Types of evolutionary trends
- Digits
- Dentition
- Relative size of the cerebral cortex
- Gestation (duration of pregnancy) and parental care
- Vision
Evolution of digits
- Primates are pentadactyl (5 digits on each limb)
- Digits are highly mobile due to arboreal ancestry
- Digits are prehensile = grasping
- The evolutionary trend is toward increasing the ability to move digits
The thumb
- Most highly evolved digit
- Independent and opposable
- The degree of opposability varies
What do humans lack?
An opposable big toe
Nails
- Primates have nails instead of claws
- This is because nails are easier for grasping
- Nails are flattened claws
- Some primitive primates retain a toileting claw
- Nails and tactile pads evolved together
Tactile pads
- Primates developed small ridges to increase grip
- Called friction pads or fingerprints
Hand shape
- Humans have a short, broad hand with short, straight fingers and a long, strong
- thumb
- This results in a high degree of opposability for all digits
- Enables a precision grip – also seen in Cercopithecoidea (old world monkey)
How many permanent teeth do humans have?
32
Dental formula
2123/2123
Gives the number of each type of tooth found in one quarter of the jaw
How old are the oldest fossils?
Approximately 65 million years’ old
Trend in the number of teeth
- Primitive mammals had a dental formula of: 3,1,4,3
- They had a total of 44 teeth
- The gradual reduction in tooth numbers was probably related to the gradual reduction in face and jaw size that has appeared in primates
Variability in tooth form
- Lemurs and Lorises have forward slanted incisors (or canines) forming a comb for grooming
- Cercopithecoids have a diastema to accommodate for very large canines
Trend in molars
- Show very few evolutionary trends
- Early mammals had 3 cusps per molar
- Cercopitheoids have 4 cusps
- Hominoids have 5 cusps on the lower molars
Vision in early primates
- They were arboreal (tree dwelling)
- This habitat relied more on vision and less on sense of smell (olfaction)
- Resulted in a general change in skull shape
- Face became flatter and cranium larger
Observable behaviour in living primates
- Supports this shift in vision and skull shape
- Lemurs use their snout and teeth for what an ape uses its hands for
Trends in face shapes
- Flatter face
- Allowed primates to investigate objects, groom and communicate
- Seen the eyes move forward
- Allows for stereoscopic vision
o Field of view from each eye overlaps
o Permits accurate judgement of distance
o Two views are superimposed
Field of view
- Arboreal lifestyle required good depth of perception
- If you misjudge distances, you fall out of a tree
- Stereoscopic vision narrows the field of view
- Primates compensated for this by having a highly mobile neck and head
Role of rods
Important for vision in dim light and produce monochromatic (black and white) vision
Role of cones
Produce colour vision in bright light
Vision in primates
- Have both rods and cons in their retinas
- More sophisticated nerves between the eyes and the brain
- Permits more acute vision in each eye
- Greater coordination between the two eyes
- Enhances stereoscopic vision
Position/protection of the eyes
- Eyes have moved forward
- Eye socket have evolved to protect the eye
- The bone has gradually closed in the side and the back of the socket
Regions of the brain
- Region of the brain concerned with the interpretation of olfaction has decreased
- Region of the brain concerned with the interpretation of vision has increased
The cerebral cortex
- The cerebrum is responsible for complex functions
- The cerebral cortex has an important role in → vision, memory, reasoning and manipulative ability
- Both have increased enormously as primates have evolved
- Larger cerebral cortex functions have facilitated more accurate visual and tactile perception along with better coordination
- There is a greater survival chance (natural selection)
Cerebral convolutions
- The number of cerebral convolutions has increased dramatically as primates have evolved
- Permits greater surface area of the cortex which has had far reaching effects on development
o Tool making vs tool use
o Behavioural responses → grooming, allies and enemies
Gestations and parental care
- Primates are not restricted to a limited reproductive season
- Have a rhythmical sexual cycle (e.g. periods)
- Usually give birth to only one offspring at a time
- Apes and humans have very efficient placentas
- Long periods of gestation
Rodent gestation period
3 weeks (6 offspring)
Tarsier gestation period
6 months (1 offspring)
Human gestation period
9 months (1 offspring)
Primate gestation periods
- Mouse lemurs: 54-68 days
- Lemurs: 132-134 days
- Macaques: 146-186 days
- Gibbons: 210 days
- Gorillas: 255 days
- Humans: 279 days
Parental care periods for primates
- Very long
- Lemurs are weaned at 5 months
- Apes are weaned at 3-4 years
Nipples
Some lemurs have multiple nipples, but most primates have only a pair
Maturation periods
Primates have delayed maturation, and attain sexual maturity much later than other mammals
- Gives them a long period of learning
- Increases chances of offspring’s survival
