Hominid Evolution

Trends in the Primate Order

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Ben Whitten

Learning Objectives

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What trends do we need to know about?
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When looking at the trends in the order Primates, we need to consider the following:


  • Digits

  • Dentition

  • Vision and olfaction

  • Brain

  • Reproduction (gestation and parental care)


We look at how these features change from more primitive primates to more advanced primates, e.g., lemur to human.

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What are the trends in digits?
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Mobility: Increasing mobility and ability to move digits independently of one another

Opposability: First digit is opposible; an increasing length results in increased effectiveness of opposability - advanced primates have full precision grip

Claws/nails: Primitive primates retain claws on some digits, higher pimates have nails on all digits

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What are the trends in dentition?
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Number of teeth: There is a reduction in the number of teeth from 36 to 32

Size of the canines: Monkeys and apes have large canines with diastema, humans have small canines with no diastema

Molars: 4 cusp molars in monkeys to 5 cusp molars in apes and humans

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What are the trends in vision and olfaction?
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Olfaction: There is a decreased reliance in olfaction (smell) as a form of communication (reduced size of snout)

Vision: There is an increased reliance on vision as a method of communication; eyes become more forward facing (stereoscopic vision), and an increased proportion of the cerebral cortex is devoted to vision

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What are the trends in the brain?
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Size: Increasing size of the brain relative to the body

Convolutions: Gradual increase in the number of folds on the surface of the cerebrum (cerebral cortex becomes more convoluted)

Cerebral cortex: The cerebral cortex makes up an increasingly large proportion of the brain

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What are the trends in reproduction?
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Gestation: Increasing length of time between fertilisation and birth

Parental care: Increasing length of time that the offspring are dpeendent on the parent or parents

Sexual maturity: Increasing later development of sexual maturity

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Primates and Characteristics
Trends in the Primate Order
Adaptations to Bipedalism
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