Glossary of Anth Exam 4
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- the largest part of the human brain, which is split into right and left hemispheres, seat of all “higher” brain functions.
- the “little brain” tucked under the cerebrum, and important in the control of balance, posture, and voluntary movement.
- Frontal lobe
- one of the largest regions of the brain that has expanded over the course of hominid evolution, responsible for speech production.
- Prefrontal cortex
- the association cortex of the frontal lobes, located forward of the primary motor region of the precentral gyrus and the supplemental motor areas.
- Parietal lobe
- responsible for comprehension of written language
- Temporal lobe
- sits below the Sylvian fissure, responsible for speech comprehension
- Occipital lobe
- part of the brain where visual information from the eyes is initially processed
- the study of the evolution of brain structure and function.
- Encephalization quotient
- the ratio of the actual brain size of a species to its expected brain size based on a statistical regression of brain-to-body size based on a large number of species.
- Olfactory bulbs
- knoblike structures, located on the underside of the
frontal lobes, that form the termination of olfactory nerves running from the nasal region to the brain.
- Hyoid bone
- small “floating bone” in the front part of the throat, held in place by muscles and ligaments.
- cavity above the larynx at back of mouth, posterior part of the tongue, epiglottis and soft palate form boundaries of the pharynx.
- sits on top of trachea, has vocal cords which produce sound
- Supralaryngeal airway
- part of airway above larynx, area of the throat that has undergone change during hominid evolution.
- airway to the lungs
- roof of the mouth
- Cranial base flexion
- of cranial base flexion is an anatomical marker of the position of the larynx, the more flexion at the base the more sounds that one can produce
- the unique system of communication used by members of the human species
- Broca’s area
- responsible for speech production, located in frontal lobe
- Wernicke’s area
- responsible for speech comprehension, located in parietal lobe.
- Angular gyrus
- responsible for written language comprehension
- Arcuate fasciculus
- connects Wernicke’s and Brocca’s areas of the brain
- Sylvian fissure
- parts of the brain responsible for language are found along the Sylvian fissure
- Brain Lateralization
- in one function of the brain typically and consistently occurs in one hemisphere of the brain, that function is lateralized.
- words have meanings that correspond to real-world actions, events or objects
- words are composed of small sound elements called phonemes, restraints on how phonemes can be combined
- way in which words are combined are governed by specific rules
- simplified no-grammatical communication systems that arise in areas where speakers of different languages need to communicate, but are not around each other enough to learn the other’s language.
- grammatical languages that have arisen and developed, typically in colonial situations.
- symbols that can be pointed to in a sequence to form phrases, used in ape language projects
- What defines our species? How are we different from our closest living relatives and previous fossil hominids?
- Our species is commonly defined as large-brained, gracile-built, geographically-dispersed generalists that live in large social groups. Homo sapiens differ from other hominids and hominoids in their ability for symbolic behavior including language, art, mortuary practices, among other abstractions.
- What is the evidence for modernity from the archaeological record? When and where does modern human behavior arise?
- Modernity in the archaeological record has been linked to the rise of symbolic behavior and advanced tool technologies. Examples include blades and composite tools, projectile points, ornamental (portable) art and cave art, pigments, beads, among others. This evidence slowly appears in Africa as early as ~300 Ka and spreads throughout the Old World by ~50 Ka.
- What are the functions of each lobe of the brain?
- The frontal lobe has a prefrontal cortex that is responsible for “higher mental functions.” The frontal lobe is also responsible for voluntary motor functions. Functions of the frontal lobe associate with having a higher intelligence compared to other animals like forming goals and devising plans to attain them. This also includes being able to foresee consequences and interacting with the environment. Broca’s area, where speech production occurs, is located in the frontal lobe.
The parietal lobe integrates sensory knowledge, numerical information, and object manipulation. In addition, the parietal lobe has areas of visual spatial processing.
The temporal lobe is responsible for auditory functions, speech, and long-term memory. The hippocampus is located in the temporal lobe and is in charge of spatial navigation. Also in the temporal lobe are the Wernicke’s area (speech comprehension) and the Angular gyrus (written language).
The occipital lobe is the visual processing center and contains most of the visual cortex. It also allows for visual mapping along with color and spatial information.
- What area(s) of the brain have decreased/reduced through human evolution?
- Compared with other mammals, anthropoids have olfactory bulbs that are small for their overall brain size. Humans reflect a more extreme basic trend in olfactory reduction. This reduction occurred as other sensory domains (such as vision) and higher-level cognition became more important, reducing reliance on the sense of smell.
- What area(s) of the brain have increased/enlarged through human evolution?
- Humans and great apes (hominoids) show an increase in frontal lobe size compared to other primates and mammals. Modern humans have an expanded prefrontal cortex for “higher mental functions.”
- When and who (three time periods and species involved) experienced an increase in brain size throughout human evolution?
- Phase 1: Between 2 to 3 Ma, brain size increases from early australopithecines (400-500 cc) to the paranthropines (475-530 cc).
Phase 2: Around 2.4-1.4 Ma, Homo habilis experiences a brain size increase of 25-30% (509-775 cc). During 1.8 Ma-800 Ka, Homo erectus has a brain size range of 650-1251 cc.
Phase 3: At around 400-600 Ka: Archaic Homo sapiens have a brain size of 1100-1586 cc. Neandertals have a cranial capacity range of 1200-1750 cc. Modern Homo sapiens have a cranial capacity of 1290-1600 cc. Notice that the cranial capacity range in Neandertals is higher because they have a bigger body size
- What were possible selective pressures for an increase in brain size overall?
- Since brain size is scaled to body size, the initial selective pressures may have been related to increase in body size, such as predator avoidance during scavenging animal carcasses and higher caloric intake from meat and marrow. From the time of the Archaic H. sapiens (Phase 3 above), EQ increased substantially, and body size alone does not explain the brain size increase. Group
hunting of large game and/or navigating an increasingly more complex social environment may have selected to increased brain size.
- What were possible selective pressures for an increase in prefrontal cortex size?
- In part, the frontal lobe is responsible for language and may have been selected for due to the advantages that language affords our species during hunting and social living. The prefrontal cortex is responsible for higher mental functions such as anticipating consequences and initiating behaviors. Prefrontal cortex enlargement may have been selected due to complex social environments as hominid population sizes increased.
- What is the Expensive-Tissue Hypothesis? According to this hypothesis, what was the driving mechanism for increased brain size in genus Homo?
- Brain is metabolically expensive tissue and takes up approximately 16-20% of total energy and oxygen consumed by the body. During the evolution of hominids, the increase is brain size may have been diet-driven due to eating meat and marrow beginning with early members of the genus Homo. The decrease in the size of the gut to process meat and marrow freed caloric intake to be used for building a bigger brain.
- What are the four hallmarks of human language?
- First, language is spoken. An evolutionary tradeoff indicates the importance of language as a biological adaptation: Anatomical changes in the throat that allow humans to produce the large variety of sounds in spoken language make us uniquely susceptible to choking. Second, language is semantic. Words have meanings that correspond to real-world objects, events, or actions. Third, language is phonemic. The words used in language are composed of small sound elements known as phonemes. There are no semantic constraints on how those elements can be combined. Finally, language is grammatical. The ways in which words are combined in language are governed by implicit rules relating to word classes and proper word ordering in phrases or sentences.
- Where is language “produced” in the brain?
- Language involves multiple areas of the brain: Broca’s area (speech production), Wernicke’s area (speech comprehension), angular gyrus (written language comprehension), arcuate fasciculus (connects Broca’s and Wernicke’s) and the Sylvian fissure (language area).
- What part(s) of the neck anatomy is involved in sound production?
- The supralaryngeal airway is the portion of the throat and head that have undergone changes during hominid evolution and allow for sound production. This includes the larynx (voice box with vocal folds/cords) and upper portion of the pharynx.
- What is the evolutionary “trade-off” of language ability in humans?
- Humans have an enlarged supralaryngeal airway that enables speech capabilities, but also is a choking hazard.
- Why can a human produce a wider range of sounds than a chimp?
- The human larynx has moved relative to the primate position causing the expansion of the pharynx enabling humans to produce more sounds.
- What “language” capabilities do non-human primates (e.g., gorillas, chimps) have? What are they missing with respect to human language hallmarks?
- Non-human primates do not have the enlarged supralaryngeal airway to make the range of sounds that humans do. Although, a few chimps and gorillas have been taught to communicate through ASL and lexigrams. Grammar is thought to be a human trait, not observed in non-human primates. A few individual chimps have shown evidence, through ASL and lexigrams, that they are capable of understanding semantics and phonemes, but these circumstances do not exist without human intervention.
- How have researchers used the hyoid bone to make arguments about speech capabilities in Neandertals?
- A potentially more direct source of evidence about the speech abilities of Neandertals has come with the discovery of a Neandertal hyoid bone from Kebara Cave, Israel, dating to about 60,000. The hyoid is a small, free-floating bone that sits in the throat (in front of the larynx and in close association with the mandible, larynx, and other structures. The presence of a hyoid bone suggests Neandertals have speech capabilities.
- What evidence do we have from the hominid fossil record for the origins of language? Do you interpret these data to support a fast or slow evolutionary process of language acquisition?
- Evidence for language includes brain endocasts of several fossil hominids showing a trend of increasing brain size and brain lateralization, preserved hyoid bones from Neandertals and early Homo sapiens, and a trend of increased cranial base flexion beginning with the earliest bipeds. All indicate a relatively slow evolutionary trajectory towards speech production. The rate of language acquisition may not be answerable with the available evidence
- What were the possible selective pressures for the origins of language? Summarize the three scenarios?
- William Calvin suggested that the evolution of one-armed throwing, handedness, and language have a connection since they are lateralized in the left hemisphere. Calvin argues that motor control is near speech control so they could have evolved together.
Another theory is language as a replacement for grooming. Dunbar found that there was a positive statistical relationship between time spent grooming, brain size, and social group size. In other words, primates with larger brains lived in larger social groups, which required them to spend more time grooming in order to maintain social cohesiveness. Humans are an exception because at some point we increased our group size and replaced social grooming with social language.
Language has also been proposed (by Terrence Deacon) to indicate exclusive sexual relationships amongst monogamous pairs living in multimale, multifemale groups. Hunting males may have provisioned females and offspring, which in turn, enhanced the male’s reproductive success and survival of his offspring. Language may have evolved to maintain the structure of those relationships.
- The Expensive-Tissue Hypothesis shows that as brain size increases:
- gut size decreases
- Encephalization Quotient (EQ) is a measure of brain size relative to:
- body size
- Modern humans show a decrease in what lobe of the brain compared to ote primates and earlier hominids?
- Increased wealth in men is correlated to what in many cultures?
- many children
- The prevalence of severe depression may be explained with the advantageous effects of what behavior?
- What has been correlated to high rates of motorcycle accidents and alcohol binge drinking in young adult males?
- High levels of testosterone
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