Chapter 8: What It Means to be a Hominin Flashcards Preview

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Flashcards in Chapter 8: What It Means to be a Hominin Deck (40)
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"encephalization" refers to the ratio of brain size to body size; the higher this ratio for a given species, the more encephalized it is said to be


obligate bipeds

in biology, "obligate" denotes a condition of necessity; being a "biped" refers to the condition of walking on two legs; therefore, obligate bipeds walk on only two legs


conditio sine qua non

a Latin term meaning "without which there is nothing." In this context, large brains were once thought to be the preeminent hominin feature from which all else followed. We know now that this is not the case.


facultative bipedalism

adopting a two-legged posture only under particular circumstances as an exception to a habitual non-bipedal form of locomotion



indicating upright or erect posture, notably with regard to the trunk



a theoretical model proposing that early Miocene hominins may have adopted a three-limbed gait prior to bipedalism, in order to carry objects such as stones


selective differential

a measure of the probability that a given phenotype will reproduce compared to an alternative phenotype


energetic efficiency

the assessment of the relative metabolic cost of performing a given task


convective cooling

reduction of body temperature by air movement facilitating heat loss through evaporation of sweat


obstetric dilemma (OD)

the hypothesis that evolution of larger brains competed with narrowing of pelvic structure associated with adopting a bipedal gait, resulting in babies being born in a more helpless stage of development



a state at birth in which the newborn lacks the ability to provide for itself and receives food and care from its mother or other caregiver


energetics of gestation and growth (EGG)

the hypothesis that the evolution of larger brain size required babies to be born at an earlier stage of fetal development due to the increasing cost of gestation for the mother; in effect, it requires less energy to feed a newborn infant than to prolong gestation


basal metabolic rate

the amount of energy needed to sustain organ function while at rest and without needing to produce or lose body heat


last common ancestor (LCA)

a term designating that species from which diverging clades evolved



a posture in which the trunk is held more or less horizontal and approximately parallel with the surface on which the animal moves


orthograde clamber

a form of arboreal hand-assisted bipedal locomotion applied specifically to orangutans, involving extension at the knee, hip, and shoulder


home base

an area likely associated with shelter and water to which hominins would repeatedly return from foraging


concealed ovulation

ovulation occurs during that stage in a placental female mammal's reproductive cycle (estrus) during which is she receptive to sexual intercourse (either physiologically or induced through copulation); it may be signalled with swelling and reddening of the genital area, or through chemical means such as pheromones. Thus, concealed ovulation refers to the absence of signalling, such that the male is unable to detect when a female may be likely to conceive. Some recent evidence suggests that chemical signalling still occurs between human females and males.


birth spacing

the amount of time that passes between life births, e.g., birthdate to birthdate. In primate life history, birth spacing is correlated with a number of variables, including female rank, and access to food resources is a primary determinant of birth spacing



male-centred; the corresponding term for female-centred arguments is gynocentrism


time allocation

in the study of life history, time allocation studies document how much time is spent during a given time period (day, season, age stage, etc.) performing particular tasks


energy budget

a compendium of the sources and expenditures of energy, typically measured in calories or kilojoules


endurance running

the idea that our ancestors evolved the capability for long distance, metabolically efficient running as a unique aspect of human bipedal locomotion


aerobic metabolism

the conversion of glucose to energy within mitochondria in the presence of oxygen, from sources such as carbohydrates, fatty acids, and amino acids



pertaining to animals adapted for efficient running


occlusal plane

the occlusal plane refers to the orientation of the chewing (i.e., occlusal) surfaces of the upper and lower dentitions



a space between adjacent teeth in the dental row into which the protruding canine from the opposite jaw fits in a closed mouth, found in nonhuman primates and some early hominins



the conjuction of the rearward (distal, away from the midline of the mouth) and inner (lingual, or tongue-facing) surfaces of a tooth



the conjunction of the forward (mesial, toward the midline) and buccal (outer, cheek-facing) surfaces of a tooth


canine honing

sharpening, in this instance of one tooth, the upper canine, through repeated contact with another tooth, the lower third premolar