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Terms in this set (35)

dentition processing of food

Apes and humans have evolved different dental characteristics, reflecting how each uses the canine and postcanine teeth

When apes grab on to food with their front teeth, the upper canines and lower third premolars cut and shred the food. (honing complex) humans have non honing chewing

Through evolution, apes' upper canines have become large, pointed, and projecting, with a sharp edge on the back.

When the jaws are fully closed, each canine fits snugly in the diastema (The sharp edge on the back of the upper canine hones, or rubs against, a sharp edge on the front of the lower third premolar, or sectorial premolar) this is essential in apes to slice up leaves and fruit before they are chewed by the back of the teeth and swallowed

Apes' lower third premolar is also distinctive in having one large, dominant cusp on the cheek side of the tooth and a tiny cusp on the tongue side of the tooth.

In contrast, living and past hominins have small, blunt, and nonprojecting canines and no diastema.

Hominin canines wear on the tips instead of the backs

The cusps on both sides of the lower third premolars are similar in size, or at least more similar in size than are apes' cusps.

hominins do not hone their canines as they chew

Hone = rub

In humans, the temporalis muscle is vertically oriented, enabling a crushing ability. In nonhuman primates, this muscle is oriented horizontally, producing slicing motions.

Apes' and humans' postcanine teeth have many similar anatomical characteristics. (3rd & 4th premolars, upper & lower, have 2 cusps each; the upper molars have 4 cusps; lower molars have 5 cusps; back teeth crush and slice food w/ a diff. emphasis: humans crush food more than apes do) -> apes use their molars more for slicing than crushing reflecting their plant- heavy diet

In apes and humans, grinding and slicing are facilitated by powerful chewing, or masticatory, muscles, especially the temporalis, masseter, and pterygoid muscles
drew on Thomas Huxley's anatomical research on the living apes of Africa

Darwin concluded that because of the remarkable anatomical similarity between humans and African apes, Africa was hominins' likely place of origin.

The characteristics that distinguish living humans from living apes, Darwin reasoned, derive from one key evolutionary event in their common ancestor, namely, the shift from life in the trees to life on the ground.

In Darwin's time, there were no recorded instances of apes' making or using tools, so tools appeared a uniquely human phenomenon (since then apes have been making and using tools)

He observed four characteristics that set living humans and living apes apart:
1. Humans are bipedal, apes are quadrupedal
2. humans have tiny canines, apes have large canines
3. humans rely on tools in their adaptations, apes do not
4. humans have big brains, apes have small brains

He concluded that bipedalism had freed the hands for carrying the weapons.

To manufacture and use these tools, the early humans needed great intelligence. Once they had the tools, they did not need the big canines for hunting or for defense.

Although he saw tool production and tool use as essential factors in the development of human intelligence, Darwin believed that humans' large brain resulted mainly from the presence of language in humans.

scientists now know that tool use and increase in brain size began well after the appearance of bipedalism and the reduction in canine size

Darwin proposed that hunting was at the basis of the divergence ( however archeological record suggests that hunting began much later in human evolution and the brain began to expand) -> hunting played an impt. role in LATER human evolution but NOT in hominin origins
yielded the longest continuous record of hominin evolution:

more than 6 million years, dating from before the australopithecines through the appearance and evolution of early Homo to the first modern H. sapiens

The scientists of the Middle Awash project predicted that fossils discovered by them from the Miocene and early Pliocene at Aramis would reveal hominin ancestors having a mosaic of apelike and humanlike characteristics.

among their findings were two species of a new genus of hominin, Ardipithecus, including the earlier Ardipithecus kadabba and the later Ardipithecus ramidus (in the local Afar language, ardi means "ground" or "floor" and rami means "root")

Unlike an ape's foot, however, Ardi's foot lacked the flexibility required for grasping tree limbs and moving through trees. (the foot was rigid) -> not flexible -> hominin adaptation for using the foot to propel itself forward when walking bipedally

The phalanges of the feet and hands were curved, indicating grasping capabilities similar to apes'.

In addition, Ardi's wrist lacked the articulations and specialized adaptations of today's suspensory, knuckle-walking great apes.

These details show that Ardi was adapted to life in the trees and to life on the ground. (part time biped and part time quadruped)

did not evolve from an ape that was suspensory in the trees and a knuckle walker on the ground

Ardi moved on its palms and feet along tree branches and walked upright on the ground (the intermediate form of bipedality is part of the ancestry of later hominins which became fully committed to life on the ground)
have been found in four main sites: Laetoli, in Tanzania, and Hadar, Korsi Dora, and Dikika, all in Ethiopia (Afar is the name of the local tribe on whose land the fossils were found in Ethiopia).

best-known australopithecine and is represented by dozens of individuals from Laetoli and Hadar and single individuals from Korsi Dora and Dikika, collectively dating to 3.6-3.0 mya.

The most spectacular of the Au. afarensis fossils are three partial skeletons from Hadar, Korsi Dora, and Dikika. (they represent an adult female nicknamed Lucy, and adult male, and a 3 yr old child)

Lucy stood only a little more than 1 m (about 3.5 ft) and had somewhat short legs relative to the length of the arms and body trunk. (short legs may have limited the stride in comparison w/ modern people) -> found in East Africa

However, the male stood about 1.5-1.7 m (about 5-5.5 ft), and the features of the skeleton and limb bones indicate that the form of walking was likely quite similar to modern humans'. (shoulder was similar to modern human's)

This similarity suggests that Lucy's legs were not short because it had some form of limited bipedality. Rather, Lucy simply was short

the adult skeleton has changed little in overall plan since the time when Au. afarensis lived on the African landscape

The phalanges from Lucy's skeleton are the same length as modern humans', but they are curved, like the pre-australopithecines'. (suggests some potential arboreal locomotion using the hands)

shoulder joints (scapulae) indicate suspensory locomotion

displays a combo of apelike and humanlike anatomical features

Au. afarensis clearly was an efficient, habitual biped that spent most of its time on the ground.

The cranial capacity of this creature and others from the taxon is about 430 cc, that of a small brain, the size of an ape's.

The apelike characteristics of the bone associated with speech indicate the strong likelihood that this hominin did not have speech.

canines are large in comparison with later hominins', the face below the nose projects like an ape's, and overall it looks primitive.

Its many similarities with Au. anamensis indicate an ancestral-descendant link between the two.

Au. afarensis is not as primitive as the earlier hominin in that the two cusps of the lower third premolars are more equal in size.

canines are smaller than the earlier species', and the upper tooth rows are parabolic and not parallel—in other words, more like humans' than like apes'.

mandibles are larger, perhaps reflecting an increased use of the jaws in chewing.

In contrast to earlier hominins, which were mostly associated with some type of forested environment, Au. afarensis lived in various habitats, including forests, woodlands, and open country. (indicates that hominins became more successful at this time), even the tooth wear is more varied than earlier australopithecines enabling it to have a more diverse diet
At the Gona River site, in the Middle Awash region, tools have been found dating to around 2.6 mya. Though still extraordinarily primitive, the tools would have been effective at cutting, butchering, and other kinds of food processing.

The dominant tools, "chopper" tools and flakes, discovered in these early hominin sites were used to remove the meat and process the meat from various animals, mostly herbivores.

At least two activities were involved: use of flakes with sharp edges for cutting meat from bones and use of choppers and cobbles to break and smash the bones to access the protein-rich marrow.

One of the sites best known for such findings is the FLK 22 site at Olduvai Gorge, where the Leakeys found the famous Australopithecus boisei cranium in the late 1950s.

some tools have shown wear (South African caves) produced by digging in the ground esp. in termite mounds (supports the idea that early hominins ate insects in addition to meat (providing protein) -> they may have also been used for digging up edible roots

before this time, tools may not have been found b/c they were made of ephemeral (lasting for a short time) materials such as wood and grass

Other evidence suggests, however, that australopithecines used tools. (hand bones have anatomical features associated with finer manipulation than that used by living apes, and a flexor muscle that makes possible the finer precision use of the thumb and other fingers for tool production and use) = material culture for acquiring, preparing, and consuming animal sources of protein
Formerly known as Zinjanthropus boisei; a later robust australopithecine from East Africa that was contemporaneous with Au. robustus and Au. africanus and had the robust cranial traits, including large teeth, large face, and heavy muscle attachments.

(named for a benefactor who supported the discoverer's research)

genus Parathropus

from Olduvai Gorge and around Lake Turkana, dates to 2.3-1.2 mya and had a brain size of about 510 cc.

Compared with earlier australopithecines, these remarkably robust australopithecines had smaller front teeth, larger back teeth, and larger faces.

Their most visually striking characteristic was a massive attachment area, on the skull, for the temporalis muscle, resulting in a well-developed sagittal crest.

Both their premolars and their molars were enormous.

These big teeth with large chewing surfaces, combined with large chewing muscles, made robust australopithecines the ultimate grinders

greater cranial robusticity after about 2.5 mya indicates that they were increasingly focused on acquiring and eating foods that required more powerful chewing muscles than before. (ate harder foods)

evidence from stable carbon isotope ratios indicates that Au. boisei mostly ate savanna (C4) grasses.

In this way, Au. boisei was like other contemporary grass-consuming mammals (such as horses, pigs, and hippopotamuses) but strikingly different from all other hominins.

This reliance on grasses—perhaps as much as 80% of their diet was grass—would have required heavy grinding by the jaws and teeth.