The more g-loaded, the more heritable, evolvable, and phenotypically variable: Homology with humans in chimpanzee cognitive abilities
Michael A. Woodley of Menie, Heitor B. F. Fernandes, William D. Hopkins; (2015) Intelligence
We computed g-loadings for 13 cognitive tasks in chimps to test Jensen effects.
We calculated phenotypic and additive genetic variance for each task.
We obtained h2 of cognitive abilities from the same sample of chimpanzees as Hopkins et al. (2014)
The four variables were positively, strongly related, expanding on studies in humans.
Tool use showed signs of strong selection pressures in line with Primate-wide studies.
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 more g-loaded cognitive abilities would also be more heritable addition to presenting greater additive genetic variance and interindividual phenotypic variability. This pattern was confirmed with multiple analytical approaches, 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 phenotypic variance, consistent with previous findings indicating that it is associated with high interspecies variance and has evolved rapidly in comparative primate studies.
Covariation between human pelvis shape, stature, and head size alleviates the obstetric dilemma; Barbara Fischer and Philipp Mitteroecker (2015) PNAS
Because of the tight fit of the large human neonate through the narrow maternal birth canal, childbirth is remarkably difficult. In this study we show that the dimensions of head, stature, and pelvis in a human body are linked in a complex way that was not recognized before and that contributes to ameliorate this tight fit. We show that females with a large head possess a birth canal that can better accommodate large-headed neonates. Because mothers with large heads usually give birth to neonates with large heads, the detected pattern of covariation contributes to ease childbirth and has likely evolved in response to strong selection.
Compared with other primates, childbirth is remarkably difficult in humans because the head of a human neonate is large relative to the birth-relevant dimensions of the maternal pelvis. It seems puzzling that females have not evolved wider pelvises despite the high maternal mortality and morbidity risk connected to childbirth. Despite this seeming lack of change in average pelvic morphology, we show that humans have evolved a complex link between pelvis shape, stature, and head circumference that was not recognized before. The identified covariance patterns contribute to ameliorate the “obstetric dilemma.” Females with a large head, who are likely to give birth to neonates with a large head, possess birth canals that are shaped to better accommodate large-headed neonates. Short females with an increased risk of cephalopelvic mismatch possess a rounder inlet, which is beneficial for obstetrics. We suggest that these covariances have evolved by the strong correlational selection resulting from childbirth. Although males are not subject to obstetric selection, they also show part of these association patterns, indicating a genetic–developmental origin of integration.
Sexual reproduction creates variation in genetic noise.
Sexual reproducing parents: Some of their offspring will have a less noisy DNA. Some of their offspring will have a more noisy DNA. Those with a noisier DNA are more likely "to be killed" by natural selection; or to be ignored by potential mates / are less able to compete for mates.
Asexual reproduction: Without genetic mixing it's quite unlikely that there will be offspring with a less noisy DNA ("Muller's ratchet"). Among the close offspring of an asexual reproducing individual there is less variation in genetic noise than among the close offspring of sexual reproducing parents.
Sexual reproduction helps preventing the accumulation of genetic noise.
(o) A part of a sentence is completely redundant, when it can be predicted from an other part / the other parts of that sentence with complete certainty.
(o) How many parts of a picture/puzzle do we have to know to make correct predictions about (A) the picture/puzzle as a whole (B) the unknown parts of that picture/puzzle? If there is a high degree of redundancy we can make more accurate predictions (our predictions have a lower degree of uncertainty) and we can make predictions by knowing smaller parts of that picture/puzzle than if there is a low degree of redundancy.
(o) There is quite a lot redundancy in this world. By making observations on the surface of this planet (just a very small piece of the whole world) over several hundred years (in comparison to the age of the world a very short time frame) we can make quite some predictions about the world as a whole; about events that occurred millions or even billions of years ago.
[Another example of redundancy: the predictive power of a 45 min IQ-test.]