S. tchadensis, the Australopiths, & Early Homo

Question 1

What changed that caused “CHLCA” to evolved into Sahelanthropus tchadensis?

Answer 1

The forested areas of Central & Eastern Africa began to slow be replaced by open grasslands called savannas

Question 2

___ % of Africa’s forests have been replaced by savannas every ______ years since 10 MYA.

Answer 2

7-8 % of Africa’s forests have been replaced by savannas every 1 million years since 10 MYA.

Question 3

What are the major features of a savanna environment

Answer 3

Warm temperatures
Moderate rainfall
Wildfires
Seasonal droughts
Tall coarse grasses (up to 3-6 ft)
Very few trees
Large open areas
Medium-sized mammals
Many predators

Question 4

What are three reasons why S. tchadensis’ ability to be partially bipedal mae it more fit for this new environment than “CHLCA”?

Answer 4

Made it better able to safely travel across the savanna to find food.

1.) Allowed them to stand up and spot predators over tall grasses

2.) Could move over long distances to other forests to find food without getting as tired or overheated

3.) Freed up its arms to carry food back to their home

Question 5

Why didn’t S. tchadensis evolve to be fully bipedal?

Answer 5

It still lived in a mostly forested environment where much of the available food was up in the trees

(Being fully bipedal makes it harder to climb easily)

Question 6

Why is it difficult ot know how S. tchadensis lived?

Answer 6

It left behind no primary sources other than its bones.

Question 7

The best guess we have about how S. tchadensis lived is that it lived liked modern day ____ and spent 86% of its day _______.

Answer 7

The best guess we have about how S. tchadensis lived is that it lived liked modern day chimpanzees and spent 86% of its day eating, resting, and sleeping.

Question 8

What became of the “CHLCA” that stayed in the forested areas of Africa?

Answer 8

They eventually evolved into chimpanzees and bonobos.

Question 9

Around 6 MYA S. tchadensis evolved into something else that eventually, around 3.9 MYA, evolved the first members of the genus _____.

Answer 9

Australopithecus

Question 10

How were species in the genus Australopithecus different from early hominins like S. tchadensis?

Answer 10

They were …

• taller
• bigger brained
• more bipedal

Question 11

How had the environment of Africa changed from the time of S. tchadensis to the time of the Australopiths?

Answer 11

There was even more savanna (37% savanna)

Question 12

Which reliability characteristics did Raymond Dart’s “Killer Ape Theory” not have or only “sort of” have?

Answer 12

• The information in unaffected by the author’s bias
• The information is supported by reliable primary sources

Question 13

What evidence is there that our Australopith ancestors were hunted by predators rather than - as Raymond Dart believed - hunters themselves?

Answer 13

• Australopith bones were discovered in bones piles made by leopards and hyenas
• Australopith skulls were found with holes made by the teeth of a leopard
• Other hominin bones from that time were discovered that show signed of being damaged by eagles and crocodiles.
• Australopith teeth were discovered that had microscopic bits of plant matter in them

Question 14

What does the “weak ape theory” say caused the evolution of our ancestors into Australopiths?

Answer 14

Helped them better hide and avoid predators as we crossed an increased amount of savanna

Question 15

Why would increased height have made our Australopith ancestors better able to avoid predators?

(Know at least one!)

Answer 15

Helped it …

• see even better over the tall grasses of the savanna to spot predators
• scare off potential predators by looking more intimidating

Question 16

Why would being more bipedal have made our Australopith ancestors better able to avoid predators?

(Know at least one!)

Answer 16

Helped it …

• Better scan the horizon to spot predators
• Move more quickly across the savanna
• Throw things at predators

Question 17

Why would have larger brains have made our Australopith ancestors better able to avoid predators?

(Know at least one!)

Answer 17

Helped it …

• manage and build larger communities (about 55 in a group) to avoid predators.
• make better plans for how to avoid predators
• develop language to plan out what to do when predators arrive

Question 18

What did Australopiths do to make up for the lessened amount of food they could get access to when they became fully bipedal?

Answer 18

They invented stone flakes to carve the meat off of the bones of animal carcasses they found on the savanna.

Question 19

What three primary sources prove that Australopiths were scavenging for meat?

Answer 19

• Stone flakes
• Animals bones with scrap marks on them
• Australopiths’ thicker teeth

Question 20

When our ancestors started using stone tools, it marks the beginning of what era of human history?

Answer 20

The Paleolithic Era (Old Stone Age)

Question 21

What four new traits did some Australopiths develop as the savanna increased in size that evolved it into Homo habilis?

Answer 21

More Bipedal (first to have Homo sapiens-like feet)

Shorter (4 ft.)

Arms & legs the same length

Bigger brain (600 cc)

Question 22

Why did Homo habilis develop these traits?

Answer 22

Made it better able to avoid predators on the savanna

Question 23

What happened to the planet around 2.5 MYA?

Answer 23

The average temperature of the planet dropped low enough for the earth to have officially entered into an “Ice Age.”

Question 24

What happens during Ice Ages?

Answer 24

The earth climate repeatedly changes between glacial periods and interglacial periods.

Question 25

What is a glacial period?

Answer 25

Very cold periods of time during Ice Ages (that usually last about 100,000 years) during which glaciers cover large parts of the world & water levels decrease

Question 26

What is an interglacial period?

Answer 26

Warmer periods of time during Ice Ages (that usually last about 10,000 years) during which many of the glaciers melt & water levels increase

Question 27

What did the beginning of the Ice Age prompt Homo habilis to evolve into?

Answer 27

Homo ergaster

Question 28

What did the discovery in Western Asia of Homo ergaster bones with several Homo habilis-like features cause historians to claim?

Answer 28

Sometime before 1.78 MYA, some Homo habilis left Eastern Africa, migrated north to Western Asia, and evolved into Homo ergaster

Question 29

What are four theories on why Homo habilis migrated out of Africa?

Answer 29

1.) Ice Age climate changes decreased their food supplies and forced them to move to new environments to look for food.

2.) Land bridges between continents formed that made it easier for them to travel outside of Africa

3.) Being more bipedal made them better able to travel longer distances than the hominins that came before them

4.) Larger brains could help them deal with unfamiliar environments (better tools, larger groups)

Question 30

What four new traits did Homo ergaster have?

Answer 30

Totally bipedal

Taller (5 ft. - 5.5 ft.)

Longer legs, shorter arms

Bigger brain (860 cc)

Question 31

Why did Homo ergaster develop these new traits?

Answer 31

Made them better able to avoid predators