Lecture 12 - Skull Comparison

Question 1

Why is evolution important?

Answer 1

Most anatomical structures are fundamentally related to function Understanding how they were
used helps us to understand past behavior
Humans are primates
o Forward facing eyes –> depth perception
o Grasping hands and feet
o Nails instead of claws –> Increases ability to manipulate things with hands and feet
o Large brain for body size –> Brain expansion

Question 2

Which primates may humans have originated from?

Answer 2

Haplorphines not lemorphines

Question 3

How do humans differ to great apes

Answer 3

1) Gait (paritcular way of walking) We are bipedal, where other apes swing through the trees. Most of our anatomy is due to
the fact that we walk habitually on 2 legs
2) Larger Brain Size Which affects the size and shape of the skull relative to our body size
3) Senses Apes are more reliant on sense organs, where we rely on other senses more heavily
4) Diet A tough diet requires a larger jaw. If the food is processed outside our mouth (cooking etc)
then there are different mechanics involved, so we don’t need big teeth or jaws
5) Communication Facial expression. Different muscles have developed due to developed social
cues
6) Mating Systems The way that we compete for mates is different to how apes do

Question 4

Gait: - Major Differences

Answer 4

• Humans are bipedal, meaning we are constantly in an upright stance. This becomes unstable
  unless we are adapted to it
• Where the spine enters the skull has changed
• In humans it is directly under the centre of the skull (Foramen Magnum)
• In other mammals and apes, the Foramen Magnum is more posterior for quadrupedal locomotion
  **- This adaptation in humans is necessary to allow the skull to face forward in an upright posture **

Question 5

Brain Size (And Shape): - Major Difference

Answer 5

• A Larger brain requires expansion of the brain case
• Humans have a much larger cranial capacity than other
  apes in comparison to body size (4x bigger than expected for our body size)
• Not just change in size, but change in shape too
• Expansion of the parietals and taller vaults
• Humans have a more globular shaped skull, where Chimps have an elongated brain case
• Humans have become more sophisticated in intelligence due to shape of skull changing allowing for certain areas of the brain to expand
• Also the skull becoming bigger to allow more space for brain

Question 6

Importance of Different Senses: -Major Difference

Answer 6

 The relative size of the area correlates to how important that sense is for that species
 All primates are visually orientated, however the relative importance of other senses varies
 Prognathism partially related to relative importance of the olfactory system (smell)  Also partially
related to need for large masticatory muscles