The target article nicely elaborates the strong relationship between cultural group selection and gene-culture coevolution. Richerson et al. correctly observe that gene-culture coevolution significantly strengthens genetic group selection models. However, there really are no purely genetic group selection models in the literature. All such models employ the phenotypic gambit (Grafen Reference Grafen, Krebs and Davies1984), in which complex transmission processes are treated as though they were the product of a single allele of the genome. Such models represent equally any transmission process, cultural, genetic, or interaction between the two, that depend only on vertical transmission from parents to offspring (Gintis Reference Gintis2014).
The target article's contention that cultural group selection is “a basic explanation for our species' highly unusual ability to create large societies with widespread cooperation between non-relatives” (sect. 7, para. 2) is incorrect. Cultural group selection is not an explanation of anything. Rather, it is a framework within which such an explanation can fruitfully be developed. The main features of human cooperation, which include collective child-rearing without a reproductive division of labor (Hrdy Reference Hrdy2000; Wilson Reference Wilson2012), hunting large game with lethal weapons (Wrangham & Carmody Reference Wrangham and Carmody2010), altruistic cooperation and punishment (Bowles & Gintis Reference Bowles and Gintis2011), as well as collaborative skills depending on a theory of mind (Tomasello Reference Tomasello2008), follow from the particular evolutionary history of our species.
Curiously, the authors suggest that there is evidence for culture-led gene-culture coevolution only “for a few simple genetic traits” (sect. 2.2, para. 6). In fact, there is overwhelming evidence for this process as central to the constitution of Homo sapiens, a few pieces of which I will cite here.
Human Self-domestication: Darwin noticed that selective breeding of mammals for tameness entailed a pattern of similar side-effects of domestication to human society in distinct species. Darwin even suggested that, “Man in many respects may be compared with those animals which have been long domesticated” (Darwin Reference Darwin1871, Ch. 7, p. 172). Belyaev (Reference Belyaev1979) corroborated this insight, studying captive silver foxes bred for tameness. These animals developed humanly attractive faces with short snouts, floppy ears, patches of white fur on their heads, and curly tails (Gibbons Reference Gibbons2014). More recently, Cieri et al. (Reference Cieri, Churchill, Franciscus, Tan and Hare2014) documented domesticated syndrome changes in human evolution since the Middle Stone Age and Upper Paleolithic, and Wilkins et al. (Reference Wilkins, Wrangham and Tecumseh Fitch2014) have proposed a general genetic model explaining the domestication phenomenon.
This is evidence for a very straightforward culture-led group selection mechanism in which an increasingly complex division of labor and social norms that rewarded cooperation (Tomasello Reference Tomasello2014) favored genetic changes that produced a more domesticated and prosocial human disposition.
Control of Fire and the Reorganization of the Human Upper Torso: Prior to the control of fire, hominins inhabited trees at night as a defense against predators. Because predators have an instinctive fear of fire, the control of fire permitted hominins, who were already bipedal, to abandon climbing almost completely (Wrangham & Carmody Reference Wrangham and Carmody2010). The lack of need for brachiation freed the hand, arms, and shoulders of proto-humans to evolve for other purposes (Gintis et al. Reference Gintis, van Schaik and Boehm2015).
Lethal Weapons and the Physiology of Throwing: Hominins developed the use of long-range projectile weaponry, and such techniques were central to human social life (Bingham Reference Bingham1999; Wilkins et al. Reference Wilkins, Schoville, Brown and Chazan2012). Humans are unique in possessing the neural machinery for rapid manual-brachial movements that allows for precision stone-throwing, which depends on the brain's capacity to orchestrate a series of rapidly changing muscle movements (Calvin Reference Calvin1983). Roach et al. (Reference Roach, Venkadesan, Rainbow and Lieberman2013) showed that Homo erectus had already evolved this capacity for accurate overhead throwing. Humans are unique in possessing a torso musculature optimized for the powerful and accurate throwing of projectile weapons.
Language and the Physiology of Communication: The increased social importance of communication in human society rewarded genetic changes that facilitate speech. Regions in the motor cortex expanded in early humans to facilitate speech production. Concurrently, nerves and muscles to the mouth, larynx, and tongue became more numerous to handle the complexities of speech (Jurmain et al. Reference Jurmain, Nelson, Kilgore and Travathan1997). Parts of the cerebral cortex, Broca's and Wernicke's areas, which do not exist or are relatively small in other primates, are large in humans and permit grammatical speech and comprehension (Belin et al. Reference Belin, Zatorre, Lafaille, Ahad and Pike2000; Binder et al. Reference Binder, Frost, Hammeke, Cox, Rao and Prieto1997).
Modern humans have a larynx low in the throat, a position that allows the throat to serve as a resonating chamber capable of a great number of sounds (Relethford Reference Relethford2007). The first hominids that had skeletal structures supporting this laryngeal placement were the Homo heidelbergensis, who lived from 800,000 to 100,000 years ago. In addition, the production of consonants requires a short oral cavity, whereas our nearest primate relatives have much too long an oral cavity for this purpose. The position of the hyoid bone, which is a point of attachment for a tongue muscle, developed in Homo sapiens in a manner permitting highly precise and flexible tongue movements.
The target article nicely elaborates the strong relationship between cultural group selection and gene-culture coevolution. Richerson et al. correctly observe that gene-culture coevolution significantly strengthens genetic group selection models. However, there really are no purely genetic group selection models in the literature. All such models employ the phenotypic gambit (Grafen Reference Grafen, Krebs and Davies1984), in which complex transmission processes are treated as though they were the product of a single allele of the genome. Such models represent equally any transmission process, cultural, genetic, or interaction between the two, that depend only on vertical transmission from parents to offspring (Gintis Reference Gintis2014).
The target article's contention that cultural group selection is “a basic explanation for our species' highly unusual ability to create large societies with widespread cooperation between non-relatives” (sect. 7, para. 2) is incorrect. Cultural group selection is not an explanation of anything. Rather, it is a framework within which such an explanation can fruitfully be developed. The main features of human cooperation, which include collective child-rearing without a reproductive division of labor (Hrdy Reference Hrdy2000; Wilson Reference Wilson2012), hunting large game with lethal weapons (Wrangham & Carmody Reference Wrangham and Carmody2010), altruistic cooperation and punishment (Bowles & Gintis Reference Bowles and Gintis2011), as well as collaborative skills depending on a theory of mind (Tomasello Reference Tomasello2008), follow from the particular evolutionary history of our species.
Curiously, the authors suggest that there is evidence for culture-led gene-culture coevolution only “for a few simple genetic traits” (sect. 2.2, para. 6). In fact, there is overwhelming evidence for this process as central to the constitution of Homo sapiens, a few pieces of which I will cite here.
Human Self-domestication: Darwin noticed that selective breeding of mammals for tameness entailed a pattern of similar side-effects of domestication to human society in distinct species. Darwin even suggested that, “Man in many respects may be compared with those animals which have been long domesticated” (Darwin Reference Darwin1871, Ch. 7, p. 172). Belyaev (Reference Belyaev1979) corroborated this insight, studying captive silver foxes bred for tameness. These animals developed humanly attractive faces with short snouts, floppy ears, patches of white fur on their heads, and curly tails (Gibbons Reference Gibbons2014). More recently, Cieri et al. (Reference Cieri, Churchill, Franciscus, Tan and Hare2014) documented domesticated syndrome changes in human evolution since the Middle Stone Age and Upper Paleolithic, and Wilkins et al. (Reference Wilkins, Wrangham and Tecumseh Fitch2014) have proposed a general genetic model explaining the domestication phenomenon.
This is evidence for a very straightforward culture-led group selection mechanism in which an increasingly complex division of labor and social norms that rewarded cooperation (Tomasello Reference Tomasello2014) favored genetic changes that produced a more domesticated and prosocial human disposition.
Control of Fire and the Reorganization of the Human Upper Torso: Prior to the control of fire, hominins inhabited trees at night as a defense against predators. Because predators have an instinctive fear of fire, the control of fire permitted hominins, who were already bipedal, to abandon climbing almost completely (Wrangham & Carmody Reference Wrangham and Carmody2010). The lack of need for brachiation freed the hand, arms, and shoulders of proto-humans to evolve for other purposes (Gintis et al. Reference Gintis, van Schaik and Boehm2015).
Lethal Weapons and the Physiology of Throwing: Hominins developed the use of long-range projectile weaponry, and such techniques were central to human social life (Bingham Reference Bingham1999; Wilkins et al. Reference Wilkins, Schoville, Brown and Chazan2012). Humans are unique in possessing the neural machinery for rapid manual-brachial movements that allows for precision stone-throwing, which depends on the brain's capacity to orchestrate a series of rapidly changing muscle movements (Calvin Reference Calvin1983). Roach et al. (Reference Roach, Venkadesan, Rainbow and Lieberman2013) showed that Homo erectus had already evolved this capacity for accurate overhead throwing. Humans are unique in possessing a torso musculature optimized for the powerful and accurate throwing of projectile weapons.
Language and the Physiology of Communication: The increased social importance of communication in human society rewarded genetic changes that facilitate speech. Regions in the motor cortex expanded in early humans to facilitate speech production. Concurrently, nerves and muscles to the mouth, larynx, and tongue became more numerous to handle the complexities of speech (Jurmain et al. Reference Jurmain, Nelson, Kilgore and Travathan1997). Parts of the cerebral cortex, Broca's and Wernicke's areas, which do not exist or are relatively small in other primates, are large in humans and permit grammatical speech and comprehension (Belin et al. Reference Belin, Zatorre, Lafaille, Ahad and Pike2000; Binder et al. Reference Binder, Frost, Hammeke, Cox, Rao and Prieto1997).
Modern humans have a larynx low in the throat, a position that allows the throat to serve as a resonating chamber capable of a great number of sounds (Relethford Reference Relethford2007). The first hominids that had skeletal structures supporting this laryngeal placement were the Homo heidelbergensis, who lived from 800,000 to 100,000 years ago. In addition, the production of consonants requires a short oral cavity, whereas our nearest primate relatives have much too long an oral cavity for this purpose. The position of the hyoid bone, which is a point of attachment for a tongue muscle, developed in Homo sapiens in a manner permitting highly precise and flexible tongue movements.