Flashcards in Human Change Over Time Deck (35):
What are 4 key characteristics of primates?
relatively large brain size, opposable thumbs, forward facing eye, long gestation periods
What are opposable thumbs good for?
enables a precision grip to do things like hold a pen
What families do hominoids encompass?
Great apes and lesser apes
What is a key characteristic of hominoids?
they do not have tails
What is a key characteristic of hominins?
They are bipedal (walks on 2 legs)
What is the name of the hole located at the bottom of your skull?
The foramen magnum
How have our spines changed to allow for bipedalism?
Changed from a 'C' shaped spine to an 'S' shaped spine
Why are S shaped spines better than C shaped spines for walking on 2 legs? list 2 benefits
1) The extra curve in an S shaped spine has a larger shock absorption capacity hence is stronger and can carry more weight
2) positions the center of gravity right beneath our feet so we can maintain balance when standing on 2 feet
Why do C shaped spines promote quadrupedalism?
It forces the animal to naturally bend over
How has the position of the foramen magnum changed over time?
Moved from the back of the skull towards the centre
How does a central foramen magnum support bipedalism?
It enables the skull to be balanced directly on top of the spinal chord so we can walk with our head upright.
What change has occurred to our big toe over time?
It has moved to become aligned with the rest of our toes
How does having an aligned big toe support bipedalism?
It is the last toe to leave the ground when walking and gives us a forward thrust which makes walking easier
What does having a big toe not aligned with the rest indicate about an animal's lifestyle?
It lives an arboreal lifestyle (lives in trees)
How has our pelvis changed over time?
It has become shorter and wider
How do the changes to our pelvis support bipedalism?
It creates a bowl shape which supports the upper torso and makes it easier to walk.
Why has the pelvis changed, other than to support bipedalism?
Has become rounder to enable babies with larger cranial sizes to pass through upon birth
How has our leg changed over time?
Our femur has increased in length, and the angle it makes with the shin bone has increased
How does a longer femur support bipedalism?
It allows for longer strides, so more distance can be covered with less energy
How does the increased angle the femur makes with the shin bone support bipedalism?
allow for the center of gravity to be directly beneath us and gives us increased balance on 2 legs. Also enables us to fully extend our leg
How has our jaw shape changed over time?
It has gone from box shaped to parabolic
Why has our jaw changed over time?
Our diet has become less plant based and more meat based which requires less grinding and hence not needing as strong a jaw.
How have our teeth changed over time?
They have become smaller
Why have our teeth changed over time?
Large teeth are required for grinding plant matter and seeds, but humans started eating and cooking more meat which are easy to eat hence these larger teeth weren’t necessary
How has our arm to leg length ratio changed over time?
Our arms have become shorter in comparison to our legs
What does having relatively short arms indicate?
That we don't live an arboreal lifestyle
How have our brow ridges and skull slant changed over time?
they have both decreased
Why have our brow ridges and skull slant changed over time?
Because our cranium size has increased and taken up more room.
How and why have our zygomatic arches and chaw position changed over time?
Our Zygomatic arches have reduced in size and our jaw sticks out less due to the change in our diet that requires less grinding and hence we need a smaller jaw
How and why has our cranial capacity changed?
Our cranial has increased in size and become more curved to allow for a larger brain
How and why has our nose changed over time?
Our nose has become more protruding to increase thermoregulation as a result of the increase in surface area
What are 5 selective advantages for bipedalism?
making it easier to cover long distances, enabling our hands to be free, to see predators/prey over long grass, easier thermoregulation, wind hits a greater surface area
What is cultural evolution?
The progression of socially transmitting learned behaviors to other individuals
How has biological evolution influenced biological evolution?
Increase in cranial capacity infers an increased brain size which has allowed our species to become more intelligent and communicate with one other which has enabled culture to flourish