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31 Cards in this Set
- Front
- Back
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Characteristics which make a primate:
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Depth perception (forward-facing eyes/overlapping field)
Grasping hands with opposable thumbs Big brains relative to body Long live history |
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Elliot Smith (1911)
Wood Jones (1916) |
Arboreal theory
Remote ancestors of primates were shrew-like terrestrial creatures which became arboreal Had to adapt to complex network of branches Developed depth perception and hand-grasping |
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Criticism of Arboreal theory
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Cartmill (1974) argues that Smith and Jones' Arboreal theory is not logical because most other arboreal mammals such as squirrels and opposoms lack the reduced olfactory apparatus, close-set eyes and large brains which arboreal life supposedly favoured.
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Cartmill (1974)
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Visual Predation theory
Grasping hands, close set eyes with depth perception and the correlation neurological specializations adapted because primates became predators of insects We also see this in owls and cats |
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Criticism of Visual Predation
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Sussman (1991) argues that recent research on nocturnal primates does not support the Visual Predation theory of Cartmill (1974)
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Sussman (1991)
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Angiosperm Radiation
Recent paleobotanical research shows that there was a major event w/ angiosperms and dispersal in the Eocene Primates are a result of coevolution with flowering plants, as primates bats and birds first arose @ Paleo-Eocene boundry |
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Dunbar (1998)
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Social Brain Hypothesis
Brains are very costly to evolve/maintain. Don't evolve for the sake of it Primates' big brains reflect the demands of complex social systems. ie Tactical deception and Coolition formation Primate social systems are undeniably more complex than those of other species |
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Sexual Dimorphism
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Sexual dimorphism is a phenotypic difference between males and females of the same species, meaning that there are obvious differences between the male and female of the species. Examples include differences in morphology, size, ornamentation and behavior.
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Trivers (1972)
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The sex who has to invest more, typically females, are choosier in their mates as they have more to lose.
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Bateman's Principal (1948)
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This causes males to have more variable reproductive success.
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Hrdy (1981)
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Because females are the choosier sex, they largely determine the evolutionary direction of the species.
This is because it is the traits which are more favoured by women which will get passed on. |
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The role of mating systems in Sexual Dimorphism
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Sexual dimorphism in primates is most prominent in - polygynous groups
- less so in multimale-multifemale societies - and minimal in monogamous species (Clutton-Brock et al 1977) |
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Rensch's rule
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Sexual dimorphism in body size increases with body size
New world monkeys have lower sexual dimorphism than Old word monkeys and apes |
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Kay et al (1988)
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Found that the more male-male competition a New World monkey species had, the higher level of sexual dimorphism in canines (males had larger canines)
Did this by sorting New World monkey by degree of inter-male competition |
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Fisher’s “Sexy Sons” theory (1930)
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Women select males with traits which will make their sons sexually attractive (thus increasing their sons and their own reproductive success).
Providing there is no cost associated with choosing these characteristics, there will be a fast evolution of the trait. |
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The appearance of sexual dimorphism in primates can be explained by sexual selection.
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This is because traits like larger body size, larger canines and masculine adornments (bright skin colours etc) are sexually selected in by females, as signs of strength, health, attractiveness (inter (intercourse)) or are helpful in helping men beat other men (intra (intrinsic))
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Zahavi (1975)
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Exaggerated secondary sexual characteristics evolve to show that, despite their costliness, that individual's genes are strong/healthy enough to bear the cost of their development
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Examples of sexual adornments and ornamentation in primates (inter)
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Brightly coloured face of male mandrill when compared to female (Setchell 1999)
Guenons bright red penis and bright blue testicles surrounded by white fur, to attract the ladies (Palvan 2001) Cape of hair on adult male hamadryas baboons (Zuckerman and Parkes 1939) |
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Examples of sexual size dimorphism in primates (intra)
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In gorillas, orangutans, mandrills, baboons, and proboscis monkeys, males are sometimes more than twice as large as females (Palvcan 2001)
Cercopithecoid male canine teeth tend to be very long and dagger-like, and can be up to 400% taller than those of females (Palvcan 2001) |
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Stevens et al 2013
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In a paper published online in Nature on the 15th May 2013, Stevens et al describe two fossils, a lone tooth and a jaw fragment with three teeth, found in Tanzania.
Precise dating of surrounding geology makes them 25mya, placing them in the Oligocene |
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Stevens et al 2013
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High-res computer scans of the fossils suggest a common ancestor for Old world monkeys and Apes was 25mya.
This confirms previous "molecular clock" DNA analysis which suggested that Old World monkeys and apes split from their common ancestor 25 million to 30 million years ago. |
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Stevens et al 2013
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The new primates are two separate genera
They bear the species names "fleaglei" and "gunnelli" after noted Primatologists Fleagle and Gunnell |
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Aegyptopithecus zeuxis
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Lived 35-33 million years ago in the early part of the Oligocene epoch, in Egypt
Is an early fossil catarrhine that predates the divergence between hominoids (apes) and Old World monkeys Could this be an ancestor of Stevens et al's (2013) new primate discoveries? (one of which has the species name "fleaglei" to honour primatologist Fleagle.) |
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Primate ancestors Ogliocene:
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*Ogliocene 34-23 mya*
35 - Aegyptopithecus 25 -Stevens et al 2013 "fleaglei" and "gunnelli" |
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Plesiadapiformes
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Plesiadapiformes are small, shrew-like mammals from the Eocene (56-33 mya).
It is conventionally argued that Plesiadapiformes are the ancestors of modern primates, potentially of lemurs or lorises. |
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Begun 2003 ---- Ape Evolution
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During the Miocene epoch (23-5 mya), as many as 100 species of apes roamed throughout the Old World
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Gigantopithecus blacki and co
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Gigantopithecus an extinct genus of ape that existed from roughly nine million years to as recently as one hundred thousand years ago (China, India, Vietnam)
This places Gigantopithecus in the same time frame and geographical location as several hominin species |
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Gigantopithecus (9mya -100kya)
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The species Gigantopithecus blacki were the largest apes that ever lived, standing up to 9.8 ft
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Gigantopithecus Locomotion debate
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Gigantopithecus's method of locomotion is uncertain, as no pelvic or leg bones have been found.
The dominant view is that it walked on all fours like modern gorillas and chimpanzees (weight too much for two legs to bear) However, a minority opinion favors bipedal locomotion. Jawbone widens towards rear, allowing room for windpipe within jaw and the skull sitting atop spine, as in humans |
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Ciochon et al 1996
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H. erectus and G. blacki coexisted in East Asia in the Pleistocene, between 1.5 and 0.5 million years ago.
During this period, blacki underwent no morphological changes apart from getting progressively larger. The hominins however underwent speciation (ergaster and erectus). |
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Primate ancestors review!
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56-33 - Eocene - Plesiadapiformes
35 - early Ogliocene - Aegyptopithecus 25 - late Ogliocene - "fleaglei" and "gunnelli" 9+ - Miocene* - Gigantopithecus * and through the Plio/Pleistocene up to 100kya |
