The more g-loaded, the more heritable, evolvable, and phenotypically variable: Homology with humans in chimpanzee cognitive abilities

Abstract

Expanding on a recent study that identified a heritable general intelligence factor (g) among individual chimpanzees from a battery of cognitive tasks, we hypothesized that the cognitive abilities that are more g-loaded would be more heritable and would present more additive genetic variance, in addition to showing more phenotypic variability. This pattern was confirmed, and is comparable to that found in humans, indicating fundamental homology. Finally, tool use presented the highest heritability, the largest amount of additive genetic variance and of phenotypic variance, consistent with previous findings indicating that it is associated with high interspecies variance and evolutionary rates in comparative primate studies.

The evolution of general intelligence

“…Highly specialized abilities are proposed to be species-typical and monomorphic, with little to no interindividual variation (Tooby & Cosmides 1990). Consistent with this, human and nonhuman primate data indicate that cognitive functions that are more specialized (and thus less g-loaded) exhibit lower phenotypic and genetic variability (Spitz 1988;Woodley of Menie et al 2015). The presence of ceiling or floor effects in measurement when testing abilities in a given species also, by definition, limits variation.…”

“…Identifying biological or cognitive correlates of g and G is a useful approach to this question, but correlation is not causation, and so the cause(s) of g and G remain unclear. An additional note on the topic of selection is that, contrary to the target article (and Woodley et al 2015), greater heritability does not indicate stronger recent selectionin fact, all else being equal, the opposite is true (Fisher 1930).…”

Filling in the Gaps: The Association between Intelligence and Both Color and Parent-Reported Ancestry in the National Longitudinal Survey of Youth 1997

“…While some argue that Jensen effects are readily accountable in terms of cultural factors [52], it so happens that known environmental effects generally do not produce these. This includes adoption gains [53], gains from educational programs like Head Start [54], gains from learning potential programs [55], practice and retest gains [55], secular gains [56], the effects of lead exposure [57], iodine deficiency [58], prenatal toxins like cocaine and alcohol [58], or the effect of traumatic brain injury [58], and environmentality in general [59]. The reason seems to be that environmental effects tend to have larger effects on specific and broad abilities (i.e., Stratum I and II in the conventional three-stratum model of intelligence) than on general mental ability, as indicated by the negative correlation between vectors [60].…”

Holocene selection for variants associated with cognitive ability: Comparing ancient and modern genomes

“…The existence of these species differences furthermore indicates that GCA has been under directional selection, particularly in the primate clade. This seems to be especially true in the case of abilities associated with tool-use, which in primates are among the most strongly associated with GCA, in addition to being the most heritable and are also associated with the strongest signals of recent directional selection (8,9). This is consistent with the theoretical expectation (10) that GCA is an adaptation to coping with evolutionarily novel challenges -these being challenges that occur infrequently throughout the phylogeny of a lineage, thus cannot be solved with recourse to specialized cognitive systems (such as those associated with cheater detection or language acquisition).…”