COSTS & BENEFITS OF GROUND LIVING. COSTS & BENEFITS Major benefit – tree living = safety from predators. Major benefit – tree living = safety from predators.

COSTS & BENEFITS OF GROUND LIVING

COSTS & BENEFITS

• Major benefit – tree living = safety from predators.

COSTS & BENEFITS

• Major benefit – tree living = safety from predators.

• Cost – leaves and fruits aren’t as rich in protein or energy.

COSTS & BENEFITS

• Major benefit – tree living = safety from predators.

• Cost – leaves and fruits aren’t as rich in protein or energy.

• Life on ground = wider diet, yet predation risk is greater.

BIPEDALISM EVOLVED QUICKLY

• The change from brachiation to bipedalism probably occurred within 2.5 million years.

BIPEDALISM EVOLVED QUICKLY

• The change from brachiation to bipedalism probably occurred within 2.5 million years.

• Extensive changes to hip and leg – fast evolution = strong selective pressure.

CARRYING INFANTS

• Infants able to be born earlier and more helpless if carried.

CARRYING INFANTS

• Infants able to be born earlier and more helpless if carried.

• Human babies can’t grasp fur (as it’s not there) because they don’t have an opposable toe.

CARRYING INFANTS

• Infants able to be born earlier and more helpless if carried.

• Human babies can’t grasp fur (as it’s not there) because they don’t have an opposable toe.

• This adaptation would accelerate quickly – a partially bipedal pre-human would have a big toe facing more directly forward for walking

CARRYING INFANTS

• Infants able to be born earlier and more helpless if carried.

• Human babies can’t grasp fur (as it’s not there) because they don’t have an opposable toe.

• This adaptation would accelerate quickly – a partially bipedal pre-human would have a big toe facing more directly forward for walking = offspring having the same trait = less able to cling on = mother would have to hold onto the baby

CARRYING INFANTS

• Infants able to be born earlier and more helpless if carried.

• Human babies can’t grasp fur (as it’s not there) because they don’t have an opposable toe.

• This adaptation would accelerate quickly – a partially bipedal pre-human would have a big toe facing more directly forward for walking = offspring having the same trait = less able to cling on = mother would have to hold onto the baby = increasing advantage of having a forward facing toe.

CARRYING FOOD

• Enabled large food items to be carried back to safety =

CARRYING FOOD

• Enabled large food items to be carried back to safety = males could attract mates this way =

CARRYING FOOD

• Enabled large food items to be carried back to safety = males could attract mates this way = females then choose the ‘best providers’ for their offspring.

KEEPING COOL

• A popular theory – bipedalism evolved in order to avoid getting too hot.

KEEPING COOL

• A popular theory – bipedalism evolved in order to avoid getting too hot.

• By being upright, a human body absorbs much less heat energy than it would if exposed to the sun on all fours.

KEEPING COOL

• A popular theory – bipedalism evolved in order to avoid getting too hot.

• By being upright, a human body absorbs much less heat energy than it would if exposed to the sun on all fours.

• Hair on heads = reduced heat absorption.

KEEPING COOL

• A popular theory – bipedalism evolved in order to avoid getting too hot.

• By being upright, a human body absorbs much less heat energy than it would if exposed to the sun on all fours.

• Hair on heads = reduced heat absorption.

• Raising the body = surrounding air cools it

KEEPING COOL

• A popular theory – bipedalism evolved in order to avoid getting too hot.

• By being upright, a human body absorbs much less heat energy than it would if exposed to the sun on all fours.

• Hair on heads = reduced heat absorption.

• Raising the body = surrounding air cools it

• This hypothesis links bipedalism with the high density of sweat glands and semi-naked skin.

KEEPING COOL

• A popular theory – bipedalism evolved in order to avoid getting too hot.

• By being upright, a human body absorbs much less heat energy than it would if exposed to the sun on all fours.

• Hair on heads = reduced heat absorption.

• Raising the body = surrounding air cools it

• This hypothesis links bipedalism with the high density of sweat glands and semi-naked skin.

• Overheating could be avoided by staying in shade = less foraging time = less food.

OTHER ADVANTAGES

• Predators can be seen earlier when upright

OTHER ADVANTAGES

• Predators can be seen earlier when upright

• More effective at brandishing weapons

OTHER ADVANTAGES

• Predators can be seen earlier when upright

• More effective at brandishing weapons

• Taller body may seem larger to predators.

• https://www.youtube.com/watch?v=K8c9lemvciI