final chap 9

Question 1

lumpers

Answer 1

Researchers who prefer to lump variable specimens into a single species or taxon and who feel high levels of variation is biologically real.

Question 2

splitters

Answer 2

Researchers who prefer to split a highly variable taxon into multiple groups or species.

Question 3

Savannah Hypothesis (or Aridity Hypothesis)

Answer 3

It suggests that the expansion of the savannah (or less densely forested, drier environments) forced early hominins from an arboreal lifestyle (one living in trees) to a terrestrial one where bipedalism was a more efficient form of locomotion

Question 4

Forest Hypothesis

Answer 4

hypothesized that forested environments, rather than savannahs, were a key influence on the development of bipedalism in hominin

Question 5

Variability Selection Hypothesis

Answer 5

states that hominin groups would experience varying degrees of natural selection due to continually changing environments and potential group isolation. This would allow certain groups to develop genetic combinations that would increase their ability to survive in shifting environments. These populations would then have a genetic advantage over others that were forced into habitat-specific adaptations

Question 6

Pulsed Variability Selection Hypothesis

Answer 6

East African Rift System (EARS) and changes in deep lakes are key drivers of diversification during early human evolution.

Question 7

Several proposed selective pressures for bipedalism:

Answer 7

1. Energy conservation
2. Thermoregulation
3. Bipedalism freed up our ancestors’ hands

Question 8

Sahelanthropus tchadensis

Answer 8

• The initial discovery was made in 2001 by Ahounta Djimdoumalbaye in Chad
• Closed forest patch, palm groves, and mixed grasslands
• Most likely ate plants
• Arboreal locomotor modes
• Average brain case: 320-380cc

*small cranial capacity (360 cc) and has canines smaller than those in extant great apes, yet still larger and pointier than those in humans.

*A short cranial base and a foramen magnum (the hole through which the spinal cord enters the cranium) that is more humanlike in positioning have been argued to indicate upright walking.

• exhibits a set of a set of derived features, including a long, low cranium; a small, ape-sized brain case; and relatively reduced prognathism.

Question 9

Orrorin tugenensis

Answer 9

• dated to between 6 mya and 5.7 mya
• was discovered near Tugen Hills in Kenya in 2000 by Brigitte Senut + Mark Pickford

*Smaller cheek teeth (molars and premolars) than those in even more recent hominins (i.e., derived), thick enamel, and reduced, but apelike, canines characterize this species.

*First species that clearly indicates adaptations for bipedal locomotion, with fragmentary leg, arm, and finger bones having been found but few cranial remains

• femur that was found: indicates that Ororrin was bipedal, and recent studies suggest that it walked in a similar way to later Pliocene hominins.
• Shape of femur neck and cross-section of bone

Question 10

Ardipithecus:

Ardipithecus ramidus

(Ar. ramidus)

Answer 10

• best known of the earliest hominins
• large sample size of over 110 specimens from Aramis alone.
• Wooded woth higher water budget
• Rich flora + fauna

*Found in Ethiopia, Kenya (in the Middle Awash region and in Gona by White et.al in 1992

*opposable big toe (hallux)

*pelvis and hip show that she could walk upright (i.e., it is derived), supporting her hominin status

*small brain (300 cc to 350 cc)

*midfacial projection, and slight prognathism show retained primitive cranial features, but the cheek bones are less flared and robust than in later hominins.

*Researchers believe that Ardipithecus ramidus was able to walk upright, although not as efficiently as later humans. It possessed the musculature required for tree climbing, and while moving quadrupedally, it likely placed weight on the palms of the hands rather than on the knuckles.

• Faculative biped terrestrial/ palmigrade climber/ clamberer arboreally
• Foramen magnum beneath cranium, broad pelvis, primitive foot, no knuckle walk adaptation.

Question 11

Ardipithecus:

Ardipithecus kadabba

Answer 11

• discovered in 1997 by paleoanthropologist Dr. Yohannes Haile-Selassie

Question 12

Evolutionarily, partially in response to our increased reliance on our hands and brain, our teeth have reduced in size and our faces are flatter, or more orthognathic.

Answer 12

True

Question 13

orthognathic

Answer 13

The face below the eyes is relatively flat and does not jut out anteriorly.

Question 14

incisiform

Answer 14

An adjective referring to a canine that appears more incisor-like in morphology.

Question 15

procumbent

Answer 15

In reference to incisors, tilting forward

Question 16

canine diastema

Answer 16

A space between the teeth, usually for large canines to fit when the mouth is closed.

Question 17

Large, short molars with thick enamel allowed these early cousins of ours to grind away at fibrous, coarse foods, such as sedges, which require plenty of chewing. This is further evidenced in the low cusps, or ridges, on the teeth, which are ideal for chewing.

Answer 17

True

Question 18

Trends among early hominins include a reduction in procumbency, reduced hind dentition (molars and premolars), a reduction in canine size (more incisiform with a lack of canine diastema and honing P3), flatter molar cusps, and thicker dental enamel. All early hominins have the primitive dental formula of 2:1:2:3. These trends are all consistent with a generalist diet, incorporating more fibrous foods.

Answer 18

True

Question 19

This pattern of larger posterior dentition (even relative to the incisors and canines), thick enamel, and cranial evidence for large chewing muscles is far more pronounced in a group known as the robust australopithecines, as opposed to their earlier contemporaries or predecessors, the gracile australopithecines, and certainly larger than those seen in early Homo, which emerges during this time. This pattern of incredibly large hind dentition (and very small anterior dentition) has led people to refer to robust australopithecines as megadont hominins.

Answer 19

True

Question 20

gracile

Answer 20

Slender, less rugged, or pronounced features.

Question 21

robust

Answer 21

Rugged or exaggerated features.

Question 22

Australopithecus anamensis

Answer 22

• Currently found from sites in the Turkana region (Kenya) and Middle Awash (Ethiopia

*discovered by an Ethiopian herder named Ali Bereino

*A small brain size (370 cc), relatively large canines, projecting cheekbones, and primitive earholes show more primitive features as compared to those of more recent Australopithecines.

*indicates bipedalism is a fragment of a tibia (shinbone), which demonstrates features associated with weight transfer during bipedal walking.

Question 23

Au. afarensis

Answer 23

• oldest and most well-known australopithecine species and consists of a large number of fossil remains.
• Discovered by: Hadar, 1974
• dated to between 2.9 mya and 3.9 mya and is found in sites all along the EARS system, in Tanzania, Kenya, and Ethiopia

*Lucy : found in 1974 by Donald Johanson and dates to approximately 3.2 mya

• The canines and molars of Au. afarensis are reduced relative to great apes but are larger than those found in modern humans
• prognathic face and robust facial features that indicate relatively strong chewing musculature (compared with Homo) but which are less extreme than in Paranthropus.
• large overall size variation indicates high levels of sexual dimorphism in this species
• Skeletal evidence indicates that this species was bipedal, primarily through examining the pelvis and lower limb, which demonstrate a humanlike femoral neck, a valgus knee, and bowl-shaped hip.

Question 24

Australopithecus africanus

Answer 24

• 3.5-2.0 MYA
• Taung child (1924)
• currently dated to between 3.3 mya and 2.1 mya (Pickering and Kramers 2010), with discoveries from Sterkfontein, Taung, Makapansgat, and Gladysvale in South Africa
• relatively large brain (400 cc to 500 cc)
• small canines without an associated diastema, and more rounded cranium and smaller teeth than Au. afarensis indicate some derived traits.
• Similarly, the postcranial remains (in particular, the pelvis) indicate bipedalism
• sloping face and curved phalanges (indicative of retained arboreal locomotor abilities) show some primitive features.
• “Mrs. Ples” brain case is small in size (like apes) but has a less prognathic face and its foramen magnum is positioned more like modern humans than in African apes.

Question 25

The discoverers of Little Foot insist that other fossil finds, previously identified as Au. Africanus, be placed in this new species based on shared primitive traits with older East African Australopithecines:

Answer 25

• discovered by Ron Clarke in 1994
• These include features such as a relatively large brain size (408 cc), robust zygomatic arch, and a flatter midface.
• discoverers have argued that the heavy anterior dental wear patterns, relatively large anterior dentition, and smaller hind dentition of this specimen more closely resemble that of Au. anamensis or Au. afarensis.

Question 26

Some have suggested that the features of the robust australopithecines might have developed more in response to:

Answer 26

effectively eating fallback foods in hard times rather than indicating a lack of adaptability.

Question 27

fallback foods

Answer 27

Foods that may not be preferred by an animal (e.g., foods that are not nutritionally dense) but that are essential for survival in times of stress or scarcity.

Question 28

Paranthropus is usually referred to by scholars as the

Answer 28

“robust” australopithecine,

Question 29

Paranthropus robust features:

Answer 29

include a large, broad, dish-shaped face and zygomatic arches that are forward facing, including a large mandible with extremely large posterior dentition.

Question 30

P. aethiopicus, P. boisei and P. robustus

Answer 30

These three species have been grouped together by a majority of scholars as a genus as they share more derived features (are more closely related to each other; or, in other words, are monophyletic (A taxon or group of taxa descended from a common ancestor that is not shared with another taxon or group)) than the other australopithecines

Question 31

Much of the phylogenetic debate (and research, more generally) has revolved around

Answer 31

the shared adaptations of these “robust” australopithecines linked to a diet of hard and/or tough foods (Brain 1967; Rak 1988). This includes their large posterior dentition (they are referred to as megadonts), hyper-thick enamel, thick robust jaws, and flared zygomatic arches (Kimbel 2015; Lee-Thorp 2011; Wood 2010

Question 32

Paranthropus

Answer 32

• As a collective, this genus spans 2.7 mya to 1.0 mya, although the dates of the individual species differ.

Question 33

Earliest of the Paranthropus species, Paranthropus aethiopicus:

Answer 33

• dated to between 2.7 mya and 2.3 mya and is currently found in Tanzania, Kenya, and Ethiopia in the EARS system

*shared derived traits of large, flat premolars and molars; large, flaring zygomatic arches for accommodating large chewing muscles (the temporalis muscle); a sagittal crest for increased muscle attachment of the chewing muscles to the skull; and a robust mandible and supraorbital torus (brow ridge).

*proximal tibia indicates bipedality and similar body size to Au. afarensis.

Question 34

Paranthropus boisei

Answer 34

• discovered in 1959 by Mary Leakey
• This “robust” australopith species is distributed across countries in East Africa at sites such as Kenya (Koobi Fora, West Turkana, and Chesowanja), Malawi (Malema-Chiwondo), Tanzania (Olduvai Gorge and Peninj), and Ethiopia (Omo River Basin and Konso).
• The hypodigm (fossil) has been found by researchers to date to roughly 2.4 mya to 1.4 mya

*very large, flat posterior dentition (largest of all hominins currently known).

*Tools dated to 2.5 mya in Ethiopia have been argued to possibly belong to this species.

• cranial features of P. boisei indicating a tough diet of tubers, nuts, and seeds, isotopes indicate a diet high in C4 foods (e.g., grasses, such as sedges)
• Nutcracker Man” (Paranthropus boisei) had hyper-robust features including very large dentition, flaring zygomatic arches, a broad concave face. It had a powerful and extremely efficient chewing force.

Question 35

Paranthropus robustus

Answer 35

• Paranthropus robustus dates approximately to 2.0 mya to 1 mya and is the only taxon from the genus to be discovered in South Africa
• been found in sites all over the Cradle, such as Kromdraai B, Swartkrans, Gondolin, Drimolen, and Coopers Cave
• have been described as being less derived, more general features that are shared with both East African species
• Enamel hypoplasia is also common in this species, possibly because of instability in the development of large, thick-enameled dentition.
• Paranthropus robustus had less derived, more general features; it was not as robust as P. boisei and not as primitive as P. aethiopicus. It also appeared to be prone to a tooth defect (enamel hypoplasia), making the enamel thinner and more prone to decay

Question 36

The robust australopithecines

Answer 36

have large temporalis (chewing) muscles, as indicated by flaring zygomatic arches, sagittal crests, and robust mandibles (jawbones). Their hind dentition is large (megadont), with low cusps and thick enamel.

Question 37

The Early Stone Age (ESA)

Answer 37

The earliest described archaeological period in which we start seeing stone tool technology.

Question 38

Stone-tool (or lithic) technology

Answer 38

• defined by the fracturing of rocks and the manufacture of tools through a process called knapping (The fracturing of rocks for the manufacture of tools).
• lasted for more than 3 million years and is broken up into chronological periods called the Early (ESA), Middle (MSA), and Later Stone Ages (LSA).

Question 39

Flakes

Answer 39

The piece knocked off of a stone core during the manufacture of a tool, which may be used as a stone tool.

Question 40

Core

Answer 40

The remains of a rock that has been flaked or knapped.

Question 41

Lomekwian knappers

Answer 41

• likely aimed to get a sharp-edged piece on a flake, which would have been functional, although the specific function is currently unknown.
• Flakes were produced through indirect percussion, whereby the knappers held a rock and hit it against another rock resting on the ground

Question 42

Oldowan

Answer 42

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

*Originally discovered in Olduvai Gorge, Tanzania, but the oldest assemblage is from Gona in Ethiopia, dated to 2.6 mya

*there was an aim to get sharp-edged flakes, but this was achieved through a different production method.

*Knappers were able to actively hold or manipulate the core being knapped, which they could directly hit using a hammerstone. This technique is known as free-hand percussion, and it demonstrates an understanding of fracture mechanics.