Chapter 8: What It Means to be a Hominin Flashcards
encephalized
“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
orthograde
indicating upright or erect posture, notably with regard to the trunk
tripedalism
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
altriciality
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
pronograde
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
androcentric
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
cursorial
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
diastema
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
distolingual
the conjuction of the rearward (distal, away from the midline of the mouth) and inner (lingual, or tongue-facing) surfaces of a tooth
mesiobuccal
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
sectorial P3
in Old World primates, a lower third premolar in which the mesiobuccal surface appears as a long, sloping surface due to contact with the upper canine
intrasexual
“intra” means within; thus intrasexual variation refers to differences that exist within males or females separately
correlated response
changes that occur in one feature are consistently associated with changes occurring in another
prognathism
projection of the lower face; the gnathic portion of the face contains the upper and lower jaws
microstructure
the arrangement of cells and their associated structures that contribute to the material properties of a tissue; usually, microstructure is viewable only with the use of instruments such as microscopes and microCT scanners
relative brain size
the absolute size of the brain adjusted to reflect the absolute size of the body of which it is a part, since we expect a larger body to have a proportionately larger brain. Primates tend to have larger brains for a given body size than other mammals
scaling
in biology, refers to the pattern of change of a part in relation to a whole; may be isometric (a unit of change in body size is matched by a unit of change in the part) or allometric (the change in a apart is greater or less than the change in the whole)
endocasts
impressions of the inner surface of the cranium and outer surface of the brain, which may occur naturally as “fossils” or from moulds created in the laboratory
paleoneurology
the study of the evolution of the brain and its functions
lunate sulcus (LS)
a fissure found in the anterior portion of the occipital lobe that demarcates the primary visual cortex; readily visible in nonhuman primate brains, the LS is often not seen in humans
