Human Evolution

1
(No Transcript)
2
(No Transcript)
3
Human Evolution

• Primate Adaptations
• 1. Primate evolution provides a context for
  understanding human origins
• a. Most primates have hands and feet adapted for
  grasping
• b. Relative to other mammals, they have large
  brains and short jaws.

4

• c. They have flat nails on their digits, rather
  than narrow claws for increased manipulative
  sensitivity
• d. Well-developed parental care and complex
  social behavior
• e. Visual acuity-(stereoscopic (3D with color)

5
(No Transcript)
6

• 2. In addition to monkeys, the anthropoid
  suborder also includes four genera of apes
  Hylobates (gibbons), Pongo (orangutans), Gorilla
  (gorillas), and Pan (chimpanzees and bonobos).
• a. Modern apes are confined to the tropical
  regions of the old world.

7

• b. they evolved from old world monkeys about
  25-30 million years ago.
• c. with the exception of gibbons, modern apes
  are larger than monkeys, with relatively long
  arms and short legs, and no tails.

8

• d. Although all apes are capable of brachiating,
  only gibbons and orangutans are primarily
  arboreal.
• e. Social organization varies, with gorillas and
  chimpanzees highly social
• f. Apes have relatively larger brains than
  monkeys, and their behavior is more flexible

9

• B. Humanity is one very young twig on the
  vertebrate tree
• 1. In the continuity of life spanning over 3.5
  billion years, humans and apes have shared
  ancestry for all but the last few million years

10

• 2. Paleoanthropology is the study of human
  origins and evolution. Paleoanthropologists use
  two words that are easy to confuse but which have
  distinct meanings.
• a. Hominoid is a term referring to great apes
  and humans collectively

11

• b. Hominid has a narrow meaning, referencing the
  part of the evolutionary tree that is more
  closely related to us than to any other living
  species.

12

• c. There are two main groups of hominids the
  australopithecines which came first and are all
  extinct, and members of the genus homo, with all
  species extinct except one Homo Sapiens

13

• 3. Paleoanthropology has a history with many
  misconceptions about human evolution generated
  during the early part of the twentieth century
  that still persist in the minds of the general
  public, long after these myths have been debunked
  by fossil discoveries

14

• a. First, our ancestors were not chimpanzees or
  any other modern apes
• b. Chimpanzees and humans represent two
  divergent branches of the hominoid tree that
  evolved from a common ancestor that was neither a
  chimpanzee nor a human

15

• c. Second, human evolution did not occur as a
  ladder with a series of steps leading directly
  from an ancestral hominoid to Homo Sapiens.
• d. Human phylogeny is more like a multi-branched
  bush with our species as the tip of the only
  surviving twig.

16

• e. Third, the various human characteristics, such
  as upright posture and enlarged brain, did not
  evolve in unison. They evolved at different
  rates called mosaic evolution.
• f. There are still many questions about our
  ancestry,

17
C. Human evolution is marked by the evolution of
several major features

• 1. Brain size based on skull measurements,
  researchers have estimated that brain size in
  hominoids tripled over the past 6 million years.
• a. it increased from 400-500cm3 in hominoids
  (and modern chimpanzees) to about 1,300cm3 in
  modern humans.

18

• b. This allowed for greater language development
  and cultural complexity.
• 2. Jaw shape our hominoid ancestors had longer
  jaws (prognathic jaws) than modern humans
• a. this resulted in a flatter face and more
  pronounced chins

19

• 3. Changes in dentition based on dietary shifts
• 4. Bipedal Posture based on fossil skeletons, it
  is clear that hominoid ancestors walked on all 4
  limbs when on the ground, like modern apes.
• a. the evolution of bipedal posture is
  associated with key skeletal modifications seen
  in early hominid fossils

20

• b. this modification was helpful for tool use,
  it allowed humans to better view their
  surroundings, provided more flexibility and
  agility for posturing and movement.
• 5. Reduced size differences between the sexes
• a. male gorillas are 2x heavier than females,
  male chimps are 1.35X heavier and male humans are
  1.2X heavier.

21
6. Key changes in family Structure

• a. Insights into social behavior are derived
  from comparisons between humans and extinct
  hominoids
• b. In contrast to most ape species, monogamy or
  long term pair bonding prevails in most human
  cultures.

22

• c. Newborn infants are exceptionally dependent
  on their mothers, the duration of parental care
  and opportunities for enhanced learning is longer
  in humans than other hominoids.

23
7.Cultural Evolution

• Tool use is more sophisticated
• Use of fire
• Cave paintings
• Introduction of language
• Agricultural advances
• Skills learned from teaching and communication