My goal is to contribute to a scientific understanding of human nature, especially by demonstrating the value of evolutionary theory. Most of my current projects involve sex differences, sports, and the limitations of Blank Slate conceptions of human nature.
Men are over-represented in the arts, sciences, and sports. This has been hypothesized to reflect... more Men are over-represented in the arts, sciences, and sports. This has been hypothesized to reflect an evolved male predisposition for enduring competitiveness or long-term moti-vation to improve one’s performance and‘‘show-off.’’Evidence for thishypothesis isequivocal,however,because thereareviable alternative explanations for men’s dominance in most cultural display domains. Here, I argue that distance running is an ideal domain for addressing this issue. Distance running is ideal because it indicates enduring competitiveness, allows objective comparisons, and is accessible, acceptable, and popular for both men and women. I review recent studies and present new data showing that substantially more men than women run relatively fast in theU.S., that thissexdifferenceinrelativeperformancecan be attributed, at least in part, to men’s greater training motivation, and that this pattern has been stable for several decades. Distance running thus provides compelling evidence for an evolved ...
Much evidence indicates that men experienced an evolutionary history of physical competition, bot... more Much evidence indicates that men experienced an evolutionary history of physical competition, both one-on-one and in coalitions. We thus hypothesized that, compared to girls and women, boys and men will possess a greater motivational predisposition to be interested in sports, especially team sports. According to most scholars, advocacy groups, and the United States courts, however, this hypothesis is challenged by modest sex differences in organized school sports participation in the contemporary U.S., where females comprise 42 % of high school participants and 43 % of intercollegiate participants. We conducted three studies to test whether organized school sports participation data underestimate the actual sex difference in sports participation. Study 1 analyzed the American Time Use Survey, which interviewed 112,000 individuals regarding their activities during one day. Females accounted for 51 % of exercise (i.e., non-competitive) participations, 24 % of total sports participatio...
Sex differences in the use of competitive tactics have been well documented and may reflect evolv... more Sex differences in the use of competitive tactics have been well documented and may reflect evolved predispositions. Recent research, however, suggests these differences may be eliminated in single-sex environments. We addressed this possibility by surveying men and women about their recent experiences as members of college (n = 376) and high school (n = 485) single-sex sports teams. We focused on participants’ recollections of being targets of exclusion or overt aggression by their teammates. In both samples, women were significantly more likely than men to recall being excluded (college Odds Ratio [OR] = 2.88; high school OR = 1.67) and receiving overt verbal aggression (ORs = 9.15, 3.30). By contrast, women were significantly less likely than men to recall receiving overt physical aggression (ORs = 0.18, 0.14). Furthermore, as predicted by the male warrior hypothesis, compared to men, women were more likely to be excluded by (ORs = 4.2, 3.36) or to receive aggression from (ORs = 13.69, 3.61) teammates in a competitive context (i.e., game) compared to other contexts. This pattern was significant for aggression in both samples and for exclusion in the high school sample. Collectively, these results indicate that differences in the behavior of men and women persist in single-sex settings where groups must cooperate against opponents.
Humans are the only species capable of powerful and accurate overhand throwing. However, the evol... more Humans are the only species capable of powerful and accurate overhand throwing. However, the evolution of this ability remains underexplored. Here we draw on several lines of evidence—anatomical, archeological, cross-species comparisons, and ethnographic—to develop a scenario for the evolution of throwing. Throwing has deep roots in the primate lineage. Nonhuman primates throw projectiles during agonistic interactions but rarely to subdue prey. Thus, we argue that throwing first arose during agonistic interactions and was later incorporated into hunting by human ancestors. The fossil record indicates that anatomical adaptations for high-speed throwing in Homo first appeared about two million years ago. Once the effective use of projectile weapons became critical to success in combat and hunting, the importance of the ability to throw, intercept, and dodge projectiles would have resulted in stronger selection on males than females to become proficient at these skills because males throw projectiles more often than females in both combat and hunting.
The development of the ability to throw projectiles for distance, speed, and accuracy was a water... more The development of the ability to throw projectiles for distance, speed, and accuracy was a watershed event in human evolution. We hypothesize that throwing first arose in threat displays and during fighting and later was incorporated into hunting by members of the Homo lineage because nonhuman primates often throw projectiles during agonistic interactions and only rarely in attempts to subdue prey. Males, who threw more often than females in both combat and hunting, would have been under stronger selection than females to become proficient at the ability to throw, intercept, and dodge projectiles as throwing skills became critical to success in combat and hunting. Therefore, we predict that males, more than females, should display innate anatomical and behavioral traits associated with throwing. We use data from a variety of disciplines to discuss: the sex differences in throwing speed, distance, and accuracy; sex differences in the development of the throwing motion; inability of training or cultural influences to erase the sex differences in throwing; sex differences in the use of throwing in sports, combat, and hunting; and sex differences in anatomical traits associated with throwing that are partly responsible for male throwing superiority. These data contradict the view held by many commentators that socialization rather than innate sex differences in ability are primarily responsible for male throwing superiority. We suggest that throwing is a male adaptation.
Journal of Social, Evolutionary, and Cultural Psychology, 2012
It was still late August when one day the door to the Spanish House was flung open, and the two s... more It was still late August when one day the door to the Spanish House was flung open, and the two spinsters were forced to kneel in front of it. Dragged from her wheelchair, the old mother was forced to join them, but she was so feeble that she collapsed into a heap on the terrace. The mob yelled and screamed, banging their fists on every available surface. The old women were called “bloodsucking leeches,”“maggots,” and “intestinal parasites.”
Evolutionary psychology has provoked controversy, especially when applied to human sex difference... more Evolutionary psychology has provoked controversy, especially when applied to human sex differences. We hypothesize that this is partly due to misunderstandings of evolutionary psychology that are perpetuated by undergraduate sex and gender textbooks. As an initial test of this hypothesis, we develop a catalog of eight types of errors and document their occurrence in 15 widely used sex and gender textbooks. Consistent with our hypothesis, of the 12 textbooks that discussed evolutionary psychology, all contained at least one error, and the median number of errors was five. The most common types of errors were “Straw Man,” “Biological Determinism,” and “Species Selection.” We conclude by suggesting improvements to undergraduate sex and gender textbooks.
Abstract: Men's dominance of cultural displays has been hypothesized to reflect an evolved m... more Abstract: Men's dominance of cultural displays has been hypothesized to reflect an evolved male predisposition for enduring competitiveness. Evidence for this hypothesis is equivocal, however, because there are viable alternative explanations for men's dominance in most display domains. Here I argue that distance running is an ideal domain for addressing this issue. Distance running is ideal because it indicates enduring competitiveness, allows objective comparisons, and is accessible, acceptable, and popular for both men and ...
It is well established that men are more likely than women to engage in direct competition, but i... more It is well established that men are more likely than women to engage in direct competition, but it is unclear if this reflects social structural conditions or evolved predispositions. These hypotheses can be addressed by quantifying competitiveness in sports and testing if the sex difference is decreasing over time in the U.S., a society where social roles have converged. Study 1 assessed participation and the occurrence of relatively fast performances by masters runners (40–74 years old) at recent road races and track meets. Fast performances occurred over 20 times more often at track meets than at road races. Women comprised 55% of finishers at roads races but only 15–28% of finishers at track meets. Thus, the sex difference in masters track participation can serve as a measure of the sex difference in competitiveness. Study 2 used data from national championship meets and yearly rankings lists to test whether the sex difference in masters track participation decreased from 1988–2...
Many scientists agree that expertise requires both innate talent and proper training. Nevertheles... more Many scientists agree that expertise requires both innate talent and proper training. Nevertheless, the highly influential deliberate practice model (DPM) of expertise holds that talent does not exist or makes a negligible contribution to performance. It predicts that initial performance will be unrelated to achieving expertise and that 10 years of deliberate practice is necessary. We tested these predictions in the domain of sprinting. In Studies 1 and 2 we reviewed biographies of 15 Olympic champions and the 20 fastest American men in U.S. history. In all documented cases, sprinters were exceptional prior to initiating training, and most reached world class status rapidly (Study 1 median = 3 years; Study 2 = 7.5). In Study 3 we surveyed U.S. national collegiate championships qualifiers in sprinters (n = 20) and throwers (n = 44). Sprinters recalled being faster as youths than did throwers, whereas throwers recalled greater strength and throwing ability. Sprinters' best perform...
Medicine and science in sports and exercise, Jan 9, 2014
Studies of non-elite distance runners suggest that men are more likely than women to slow their p... more Studies of non-elite distance runners suggest that men are more likely than women to slow their pace in the marathon. This study determined the reliability of the sex difference in pacing across many marathons, and after adjusting women's performances by 12% to address men's greater maximal oxygen uptake and also incorporating information on racing experience. Data was acquired from 14 U.S. marathons in 2011, and encompassed 91,929 performances. For 2,929 runners, we obtained experience data from a race-aggregating website. We operationalized pace maintenance as percentage change in pace observed in the second half of the marathon relative to the first half. Pace maintenance was analyzed as a continuous variable and as two categorical variables: "maintain the pace," defined as slowing < 10%; and "marked slowing," defined as slowing ≥30%. The mean change in pace was 15.6% and 11.7% for men and women, respectively (P<0.0001). This sex difference was s...
Men are over-represented in the arts, sciences, and sports. This has been hypothesized to reflect... more Men are over-represented in the arts, sciences, and sports. This has been hypothesized to reflect an evolved male predisposition for enduring competitiveness or long-term moti-vation to improve one’s performance and‘‘show-off.’’Evidence for thishypothesis isequivocal,however,because thereareviable alternative explanations for men’s dominance in most cultural display domains. Here, I argue that distance running is an ideal domain for addressing this issue. Distance running is ideal because it indicates enduring competitiveness, allows objective comparisons, and is accessible, acceptable, and popular for both men and women. I review recent studies and present new data showing that substantially more men than women run relatively fast in theU.S., that thissexdifferenceinrelativeperformancecan be attributed, at least in part, to men’s greater training motivation, and that this pattern has been stable for several decades. Distance running thus provides compelling evidence for an evolved ...
Much evidence indicates that men experienced an evolutionary history of physical competition, bot... more Much evidence indicates that men experienced an evolutionary history of physical competition, both one-on-one and in coalitions. We thus hypothesized that, compared to girls and women, boys and men will possess a greater motivational predisposition to be interested in sports, especially team sports. According to most scholars, advocacy groups, and the United States courts, however, this hypothesis is challenged by modest sex differences in organized school sports participation in the contemporary U.S., where females comprise 42 % of high school participants and 43 % of intercollegiate participants. We conducted three studies to test whether organized school sports participation data underestimate the actual sex difference in sports participation. Study 1 analyzed the American Time Use Survey, which interviewed 112,000 individuals regarding their activities during one day. Females accounted for 51 % of exercise (i.e., non-competitive) participations, 24 % of total sports participatio...
Sex differences in the use of competitive tactics have been well documented and may reflect evolv... more Sex differences in the use of competitive tactics have been well documented and may reflect evolved predispositions. Recent research, however, suggests these differences may be eliminated in single-sex environments. We addressed this possibility by surveying men and women about their recent experiences as members of college (n = 376) and high school (n = 485) single-sex sports teams. We focused on participants’ recollections of being targets of exclusion or overt aggression by their teammates. In both samples, women were significantly more likely than men to recall being excluded (college Odds Ratio [OR] = 2.88; high school OR = 1.67) and receiving overt verbal aggression (ORs = 9.15, 3.30). By contrast, women were significantly less likely than men to recall receiving overt physical aggression (ORs = 0.18, 0.14). Furthermore, as predicted by the male warrior hypothesis, compared to men, women were more likely to be excluded by (ORs = 4.2, 3.36) or to receive aggression from (ORs = 13.69, 3.61) teammates in a competitive context (i.e., game) compared to other contexts. This pattern was significant for aggression in both samples and for exclusion in the high school sample. Collectively, these results indicate that differences in the behavior of men and women persist in single-sex settings where groups must cooperate against opponents.
Humans are the only species capable of powerful and accurate overhand throwing. However, the evol... more Humans are the only species capable of powerful and accurate overhand throwing. However, the evolution of this ability remains underexplored. Here we draw on several lines of evidence—anatomical, archeological, cross-species comparisons, and ethnographic—to develop a scenario for the evolution of throwing. Throwing has deep roots in the primate lineage. Nonhuman primates throw projectiles during agonistic interactions but rarely to subdue prey. Thus, we argue that throwing first arose during agonistic interactions and was later incorporated into hunting by human ancestors. The fossil record indicates that anatomical adaptations for high-speed throwing in Homo first appeared about two million years ago. Once the effective use of projectile weapons became critical to success in combat and hunting, the importance of the ability to throw, intercept, and dodge projectiles would have resulted in stronger selection on males than females to become proficient at these skills because males throw projectiles more often than females in both combat and hunting.
The development of the ability to throw projectiles for distance, speed, and accuracy was a water... more The development of the ability to throw projectiles for distance, speed, and accuracy was a watershed event in human evolution. We hypothesize that throwing first arose in threat displays and during fighting and later was incorporated into hunting by members of the Homo lineage because nonhuman primates often throw projectiles during agonistic interactions and only rarely in attempts to subdue prey. Males, who threw more often than females in both combat and hunting, would have been under stronger selection than females to become proficient at the ability to throw, intercept, and dodge projectiles as throwing skills became critical to success in combat and hunting. Therefore, we predict that males, more than females, should display innate anatomical and behavioral traits associated with throwing. We use data from a variety of disciplines to discuss: the sex differences in throwing speed, distance, and accuracy; sex differences in the development of the throwing motion; inability of training or cultural influences to erase the sex differences in throwing; sex differences in the use of throwing in sports, combat, and hunting; and sex differences in anatomical traits associated with throwing that are partly responsible for male throwing superiority. These data contradict the view held by many commentators that socialization rather than innate sex differences in ability are primarily responsible for male throwing superiority. We suggest that throwing is a male adaptation.
Journal of Social, Evolutionary, and Cultural Psychology, 2012
It was still late August when one day the door to the Spanish House was flung open, and the two s... more It was still late August when one day the door to the Spanish House was flung open, and the two spinsters were forced to kneel in front of it. Dragged from her wheelchair, the old mother was forced to join them, but she was so feeble that she collapsed into a heap on the terrace. The mob yelled and screamed, banging their fists on every available surface. The old women were called “bloodsucking leeches,”“maggots,” and “intestinal parasites.”
Evolutionary psychology has provoked controversy, especially when applied to human sex difference... more Evolutionary psychology has provoked controversy, especially when applied to human sex differences. We hypothesize that this is partly due to misunderstandings of evolutionary psychology that are perpetuated by undergraduate sex and gender textbooks. As an initial test of this hypothesis, we develop a catalog of eight types of errors and document their occurrence in 15 widely used sex and gender textbooks. Consistent with our hypothesis, of the 12 textbooks that discussed evolutionary psychology, all contained at least one error, and the median number of errors was five. The most common types of errors were “Straw Man,” “Biological Determinism,” and “Species Selection.” We conclude by suggesting improvements to undergraduate sex and gender textbooks.
Abstract: Men's dominance of cultural displays has been hypothesized to reflect an evolved m... more Abstract: Men's dominance of cultural displays has been hypothesized to reflect an evolved male predisposition for enduring competitiveness. Evidence for this hypothesis is equivocal, however, because there are viable alternative explanations for men's dominance in most display domains. Here I argue that distance running is an ideal domain for addressing this issue. Distance running is ideal because it indicates enduring competitiveness, allows objective comparisons, and is accessible, acceptable, and popular for both men and ...
It is well established that men are more likely than women to engage in direct competition, but i... more It is well established that men are more likely than women to engage in direct competition, but it is unclear if this reflects social structural conditions or evolved predispositions. These hypotheses can be addressed by quantifying competitiveness in sports and testing if the sex difference is decreasing over time in the U.S., a society where social roles have converged. Study 1 assessed participation and the occurrence of relatively fast performances by masters runners (40–74 years old) at recent road races and track meets. Fast performances occurred over 20 times more often at track meets than at road races. Women comprised 55% of finishers at roads races but only 15–28% of finishers at track meets. Thus, the sex difference in masters track participation can serve as a measure of the sex difference in competitiveness. Study 2 used data from national championship meets and yearly rankings lists to test whether the sex difference in masters track participation decreased from 1988–2...
Many scientists agree that expertise requires both innate talent and proper training. Nevertheles... more Many scientists agree that expertise requires both innate talent and proper training. Nevertheless, the highly influential deliberate practice model (DPM) of expertise holds that talent does not exist or makes a negligible contribution to performance. It predicts that initial performance will be unrelated to achieving expertise and that 10 years of deliberate practice is necessary. We tested these predictions in the domain of sprinting. In Studies 1 and 2 we reviewed biographies of 15 Olympic champions and the 20 fastest American men in U.S. history. In all documented cases, sprinters were exceptional prior to initiating training, and most reached world class status rapidly (Study 1 median = 3 years; Study 2 = 7.5). In Study 3 we surveyed U.S. national collegiate championships qualifiers in sprinters (n = 20) and throwers (n = 44). Sprinters recalled being faster as youths than did throwers, whereas throwers recalled greater strength and throwing ability. Sprinters' best perform...
Medicine and science in sports and exercise, Jan 9, 2014
Studies of non-elite distance runners suggest that men are more likely than women to slow their p... more Studies of non-elite distance runners suggest that men are more likely than women to slow their pace in the marathon. This study determined the reliability of the sex difference in pacing across many marathons, and after adjusting women's performances by 12% to address men's greater maximal oxygen uptake and also incorporating information on racing experience. Data was acquired from 14 U.S. marathons in 2011, and encompassed 91,929 performances. For 2,929 runners, we obtained experience data from a race-aggregating website. We operationalized pace maintenance as percentage change in pace observed in the second half of the marathon relative to the first half. Pace maintenance was analyzed as a continuous variable and as two categorical variables: "maintain the pace," defined as slowing < 10%; and "marked slowing," defined as slowing ≥30%. The mean change in pace was 15.6% and 11.7% for men and women, respectively (P<0.0001). This sex difference was s...
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