final chap 10

Question 1

The Pliocene (5.3 million to 2.6 million years ago)

Answer 1

marked by cooler and drier conditions, with ice caps forming permanently at the poles. Still, Earth’s climate during the Pliocene was considerably warmer and wetter than at present.

Question 2

Pleistocene “ice age” epoch (2.6 million years to 11,000 years ago)

Answer 2

climate became much more variable, cycling abruptly between warm/wet (interglacial) and cold/dry (glacial) cycles. The climate pattern was likely influenced by changes in Earth’s elliptical orbit around the sun.

Question 3

In Africa, paleoclimate research has determined that grasslands

Answer 3

expanded and shrank multiple times during this period, even as they expanded over the long term.

Question 4

During the early Pleistocene

Answer 4

there is evidence of African mammal species such as baboons, hippos, antelope, and African buffalo migrating out of Africa into Eurasia during periods when drier conditions extended out from Africa into the Middle East

Question 5

Faced with the unstable African climate and shifting landscape, the genus Homo:

Answer 5

evolved bigger brains that enabled them to rely on cultural solutions such as crafting stone tools that opened up new foraging opportunities.

Question 6

Homo habilis : “handy” or “skilled.”

Answer 6

• has traditionally been considered the earliest species placed in the genus Homo

*has a somewhat larger brain size–an average of 650 cubic centimeters (cc) compared to less than 500 cc for Australopithecus

*the skull is more rounded and the face less prognathic.

*However, the postcranial remains show a body size and proportions similar to Australopithecus.

*range from about 2.5 million years ago to 1.7 million years ago

*The first fossils to be named Homo habilis were discovered at the site of Olduvai Gorge in Tanzania, East Africa, by members of a team led by Louis and Mary Leakey

*hand bones were similar to humans’ in that they were capable of a precision grip

*had smaller molar teeth that were less “bulgy” than australopithecine teeth

*Cast of the Homo habilis cranium KNM-ER-1470. This cranium has a wide, flat face, larger brain size, and larger teeth than other Homo habilis fossils, leading some scientists to give it a separate species name, Homo rudolfensis.

*small-bodied

Question 7

The diversity of the Homo Habilis fossils prompted some scientists to :

Answer 7

question whether they displayed too much variation to all remain as part of the same species. They proposed splitting the fossils into at least two groups. The first group resembling the original small-brained specimen would retain the species name Homo habilis; the second group consisting of the larger-brained fossils such as KNM-ER-1470 would be assigned the new name of Homo rudolfensis (see Figure 10.7). Researchers who favored keeping all fossils in Homo habilis argued that sexual dimorphism, adaptation to local environments, or developmental plasticity could be the cause of the differences. For example, modern human body size and body proportions are influenced by variations in climates and nutritional circumstances.

Question 8

Analysis of the Homo Habilis relative strength of limb bones suggested:

Answer 8

that the species, though bipedal, was much more adapted to arboreal climbing than Homo Erectus and Homo sapiens.

Question 9

Oldowan

Answer 9

• Earliest stone-tool industry consisting of simple flakes and choppers.

*named after the site of Olduvai Gorge where the tools were first discovered.

*The time period of the Oldowan is generally considered to last from about 2.5 mya to 1.6 mya

*The rock selected as the core must be struck by the rock serving as a hammerstone at just the right angle so that one or more flat flakes are removed. This requires selecting rocks that will fracture predictably instead of chunking, as well as the ability to plan ahead and envision the steps needed to create the finished product. The process leaves both the core and the flakes with sharp cutting edges that can be used for a variety of purposes.

Question 10

What were the hominins doing with the tools?

Answer 10

• butchering animals : Animal bones with cut marks start appearing at sites with Oldowan tools.

*used for processing plant materials such as wood, roots or tubers, and grass seeds and stems.

Question 11

scavenging hypothesis

Answer 11

• inferred that there were scavenging opportunities for Plio-pleistocene hominins.
• When lions abandon a kill after eating their fill, scavenging animals arrive almost immediately to pick apart the carcass. By the time the slow-footed hominins arrived on the scene, the carcass would be mostly stripped of meat. However, if hominins could use stone tools to break into the leg bone cavities, they could get to the marrow, a fatty, calorie-dense source of protein

Question 12

Oldowan toolmakers were exploiting a new

Answer 12

ecological niche that provided them with more protein and calories.

Question 13

Homo erectus

Answer 13

• equipped with bigger brains and large bodies with limb proportions similar to our own.

*more advanced tools, hunting, use of fire, and colonizing new environments outside of Africa.

*Compared to Homo habilis, Homo erectus showed increased brain size, smaller teeth, and a larger body

• larger brain size (average of about 900 cc compared to 650 cc to 750 cc

*skull was long and low like a football, with a receding forehead, and a horizontal ridge called an occipital torus (A ridge on the occipital bone in the back of the skull) that gave the back of the skull a squared-off appearance

• skulls have a slight thickening along the sagittal suture called a sagittal keel (A thickened area along the top of the skull).
• Large, shelf-like brow ridges hang over the eyes.
• The face shows less prognathism, and the back teeth are smaller than those of Homo habilis. Instead of a pointed chin, like ours, the mandible of Homo erectus recedes back.
• shows evidence of being fully committed to life on the ground meaning: powerfully muscled legs that enabled these hominins to cover more ground efficiently

*Many experts think that hominins around this time had lost much of their body hair, were particularly efficient at sweating, and had darker-pigmented skin—all traits that would support the active lifestyle of such a large-bodied hominin.

• shows some evidence of a reduction in sexual dimorphism in body size compared to the earlier australopithecines.

Question 14

Asian fossils tend to have a thicker skull and larger brow ridges than the African specimens, and the sagittal keel described above is more pronounced

Answer 14

True

Question 15

One explanation for the range of body sizes:

Answer 15

• adaptation to a range of different local environments, just as humans today show reduced body size in poor nutritional environments.

Question 16

Many experts believe that the driving force behind our loss of body hair was

Answer 16

The need to effectively cool ourselves

Question 17

The earliest fossils in Africa identified as Homo erectus:

Answer 17

• East African site of Koobi Fora, around Lake Turkana in Kenya, and are dated to about 1.8 million years ago.
• Other fossil remains have been found in East African sites in Kenya, Tanzania, and Ethiopia

Question 18

The first discovery of Homo erectus was

Answer 18

• in the late 1800s in Java, Indonesia by Eugene Dubois.
• “Java Man”

*

Question 19

Homo erectus has a long history in Indonesia

Answer 19

Further discoveries of fossils from Java were dated by argon dating to about 1.6 million to 1.8 million years. A cache of H. erectus fossils from the site of Ngandong in Java has yielded very recent dates of 43,000 years, although a more recent study with different dating methods concluded that they were much older—between 140,000 and 500,000 years old.

Question 20

Evidence of Homo erectus in China :

Answer 20

Homo erectus fossils from northern China, collectively known as “Peking Man,” are some of the most famous human fossils in the world. Dated to about 400,000–700,000 years ago, they were excavated from the site of Zhoukoudian, near the outskirts of Beijing. Hundreds of bones and teeth, including six nearly complete skulls, were excavated from the cave in the 1920s and 1930s. Much of the fossils’ fame comes from the fact that they disappeared under mysterious circumstances. As Japan advanced into China during World War II, Chinese authorities, concerned for the security of the fossils, packed up the boxes and arranged for them to be transported to the United States. But in the chaos of the war, they vanished and were never heard about again.

Question 21

Site of Dmanisi in the Republic of Georgia:

Answer 21

• revealed the presence of Homo erectus in Western Eurasia between 1.75 million and 1.86 million years ago
• Fossils found: have smaller brains and bodies
• Show clear signs of Homo erectus traits such as heavy brow ridges and reduced facial prognathism
• they show a great deal of variation in brain size and in facial features
• Some contend that the Dmanisi fossils cannot all belong to a single species because each one is so different. Others assert that the variability of the Dmanisi fossils proves that they, along with all early Homo fossils, including H. habilis and H. rudolfensis, could all be grouped into Homo erectus

Question 22

Acheulean tool industry

Answer 22

• Starting at about 1.5 million years ago, some Homo erectus populations began making different forms of tools.
• Tool industry characterized by teardrop-shaped stone handaxes flaked on both sides.

*Acheulean toolmakers carefully shaped both sides of the tool.

• This type of technique, known as bifacial flaking, requires more planning and skill on the part of the toolmaker; he or she would need to be aware of principles of symmetry when crafting the tool
• most common tool forms: the handaxe, crapers, cleavers, and flake tools are present at Homo erectus sites.

Question 23

Curiously, the Acheulean tools so prominent at African sites are mostly absent in Homo erectus sites in East Asia. Instead, Oldowan-type choppers and scrapers are found at those sites. If this technology seemed to be so important to African Homo erectus, why didn’t East Asian Homo erectus also use the tools?

Answer 23

One reason could be environmental differences between the two regions. Perhaps the rocks available in Asia weren’t of the material suitable for making the Acheulean handaxes. It has been suggested that Asian Homo erectus populations used perishable material such as bamboo to make tools. Another possibility is that Homo erectus (or even an earlier hominin) migrated to East Asia before the Acheulean technology developed in Africa. The recent discovery of the 2.1 million-year-old tools in China gives credence to this last explanation.

Question 24

diet of Homo erectus evidence

Answer 24

• stone tools used by Homo erectus, animal bones and occasionally plant remains from Homo erectus sites, and the bones and teeth of the fossils themselves.
• = consumed more animal protein

Question 25

More meat in the diet would allow for a smaller gut and could also fuel the larger brain and body size seen in the genus Homo.

Answer 25

True

Question 26

Studies of the tooth surfaces and microscopic wear patterns on hominin teeth indicate

Answer 26

• That Homo erectus ate a variety of foods, including some hard, brittle plant foods
• Roots, bulbs, and tubers (known as underground storage organs) of open savanna plants may have been a primary food source.

Question 27

One key characteristic of the genus Homo is smaller teeth compared to Australopithecus. Why would teeth get smaller?

Answer 27

• type of foods eaten
• may have been changes in how food was prepared and consumed
• If hominins were using these tools to cut up, tenderize, and process meat and plants, they wouldn’t have to use their teeth so vigorously.
• Cooking food could also have contributed to the reduction in tooth and jaw size : Cooking provides a head start in the digestive process because of how heat begins to break down food before food even enters the body, and it can help the body extract more nutrients out of meat and plant foods such as starchy tubers.

Question 28

Burned areas and ash deposits must have direct associations with human activity to make a case for deliberate fire use.

Answer 28

True

Question 29

presence of wood ash in caves where trees don’t naturally grow, deep ash deposits in hearths lined with stones, or burned pieces of stone tools and butchered animal bones

Answer 29

Very rare in hominin sites

Question 30

Homo erectus is generally thought to be the first hominin species to leave the continent of Africa and settle in Eurasia in places such as the Republic of Georgia, Indonesia, and northern China:

Answer 30

• larger brain and body size of Homo erectus were fueled by a diet consisting of more meat, and longer more powerful legs made it possible to walk and run longer distances to acquire food.
• better stone tools and new technology such as fire gave them greater flexibility in adapting to different environments
• Changes in air temperature, precipitation, access to water sources, and other habitat alteration had far-reaching effects on animal and plant communities; this included Homo erectus

Question 31

Homo erectus had its own distinct growth pattern

Answer 31

reaching maturity more slowly than chimpanzees but faster than Homo sapiens.

Question 32

mosaic evolution

Answer 32

The concept that evolutionary change does not occur homogeneously throughout the body in organisms.