Skill not athleticism predicts individual variation in match performance of soccer players.

Just as evolutionary biologists endeavour to link phenotypes to fitness, sport scientists try to identify traits that determine athlete success. Both disciplines would benefit from collaboration, and to illustrate this, we used an analytical approach common to evolutionary biology to isolate the phenotypes that promote success in soccer, a complex activity of humans played in nearly every modern society. Using path analysis, we quantified the relationships among morphology, balance, skill, athleticism and performance of soccer players. We focused on performance in two complex motor activities: a simple game of soccer tennis (1 on 1), and a standard soccer match (11 on 11). In both contests, players with greater skill and balance were more likely to perform better. However, maximal athletic ability was not associated with success in a game. A social network analysis revealed that skill also predicted movement. The relationships between phenotypes and success during individual and team sports have potential implications for how selection acts on these phenotypes, in humans and other species, and thus should ultimately interest evolutionary biologists. Hence, we propose a field of evolutionary sports science that lies at the nexus of evolutionary biology and sports science. This would allow biologists to take advantage of the staggering quantity of data on performance in sporting events to answer evolutionary questions that are more difficult to answer for other species. In return, sports scientists could benefit from the theoretical framework developed to study natural selection in non-human species.

Daylight saving time can decrease the frequency of wildlife-vehicle collisions.

Daylight saving time (DST) could reduce collisions with wildlife by changing the timing of commuter traffic relative to the behaviour of nocturnal animals. To test this idea, we tracked wild koalas (Phascolarctos cinereus) in southeast Queensland, where koalas have declined by 80% in the last 20 years, and compared their movements with traffic patterns along roads where they are often killed. Using a simple model, we found that DST could decrease collisions with koalas by 8% on weekdays and 11% at weekends, simply by shifting the timing of traffic relative to darkness. Wildlife conservation and road safety should become part of the debate on DST.

Multivariate analyses of individual variation in soccer skill as a tool for talent identification and development: utilising evolutionary theory in sports science.

The development of a comprehensive protocol for quantifying soccer-specific skill could markedly improve both talent identification and development. Surprisingly, most protocols for talent identification in soccer still focus on the more generic athletic attributes of team sports, such as speed, strength, agility and endurance, rather than on a player's technical skills. We used a multivariate methodology borrowed from evolutionary analyses of adaptation to develop our quantitative assessment of individual soccer-specific skill. We tested the performance of 40 individual academy-level players in eight different soccer-specific tasks across an age range of 13-18 years old. We first quantified the repeatability of each skill performance then explored the effects of age on soccer-specific skill, correlations between each of the pairs of skill tasks independent of age, and finally developed an individual metric of overall skill performance that could be easily used by coaches. All of our measured traits were highly repeatable when assessed over a short period and we found that an individual's overall skill - as well as their performance in their best task - was strongly positively correlated with age. Most importantly, our study established a simple but comprehensive methodology for assessing skill performance in soccer players, thus allowing coaches to rapidly assess the relative abilities of their players, identify promising youths and work on eliminating skill deficits in players.

Does individual quality mask the detection of performance trade-offs? A test using analyses of human physical performance.

Why are performance trade-offs so rarely detected in animals when their underlying physiological basis seems so intuitive? One possibility is that individual variation in health, fitness, nutrition, development or genetics, or 'individual quality', makes some individuals better or worse performers across all motor tasks. If this is the case, then correcting for individual quality should reveal functional trade-offs that might otherwise be overlooked. We tested this idea by exploring trade-offs in maximum physical performance and motor skill function in semi-professional soccer players. We assessed individual performance across five maximum 'athletic' tasks providing independent measures of power, stamina and speed, as well as five soccer-specific 'motor skill' tasks providing independent measures of foot control. We expected to find functional trade-offs between pairs of traits (e.g. endurance versus power/speed tasks or specialist-generalist performance) - but only after correcting for individual quality. Analyses of standardised raw data found positive associations among several pairs of traits, but no evidence of performance trade-offs. Indeed, peak performance across a single athletic task (degree of specialisation) was positively associated with performance averaged across all other athletic tasks (generalist). However, after accounting for an individual's overall quality, several functional trade-offs became evident. Within our quality-corrected data, 1500 m-speed (endurance) was negatively associated with squat time (power), jump distance (power) and agility speed - reflecting the expected speed-endurance trade-off; and degree of specialisation was negatively associated with average performance across tasks. Taken together, our data support the idea that individual variation in general quality can mask the detection of performance trade-offs at the whole-animal level. These results highlight the possibility that studies may spuriously conclude certain functional trade-offs are unimportant or non-existent when analyses that account for variation in general quality may reveal their cryptic presence.

Pre-cleaning of hair is not beneficial in LA-ICP-MS studies of chronic metal exposure.

Chronic exposure to toxic metals is a serious global health concern. However, population-wide biomonitoring is costly and carries several sampling constraints. Though hair sampling can be a useful way to assess environmental exposure, external contamination is a long-standing concern, and a pre-cleaning step prior to metal quantification has long been recommended despite a lack of evidence for its efficacy. In this study, we quantified the spatial distribution of 16 elements in unwashed human hair samples using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), then tested how two common pre-cleaning treatments (Triton-ethanol, Triton-nitric acid) affected metal content in external and interior layers of hair using LA-ICP-MS. We show that elements differ in their spatial distribution across hair and that pre-cleaning is not consistent in its effect on element concentrations and decreases interior concentrations of some elements. We demonstrate that differences among individuals can be quantified reliably with LA-ICP-MS analysis of interior concentrations of unwashed hair. Our study tests the widespread notion that pre-cleaning is essential in analyses of hair for environmental exposure to metals, and examines the benefits of a unified approach to analysis of metals in hair using LA-ICP-MS.

Females prefer athletes, males fear the disadvantaged: different signals used in female choice and male competition have varied consequences.

The most commonly assumed cost for exaggerated male ornamentation is increased predation pressure owing to decreased locomotor performance or increased conspicuousness to predators. Despite its intuitive basis, the locomotor costs of male ornamentation are not well established. We tested the hypothesis that multiple male signals that are used independently during female choice and male competition could lead to varied locomotor costs. Multiple signals with varied costs could provide a more detailed indicator of overall male quality, as only the highest-quality individuals could support all costs. To test this idea, we investigated the burst locomotor consequences of multiple ornaments for males of the pacific blue-eye (Pseudomugil signifer). We evaluated five competing models relating body size, ornament size and performance traits to field measures of dominance and attractiveness. Non-propulsive male fin ornaments used during male competition were different from those used in female choice. First dorsal fin length was the most important predictor of male attractiveness, while dominance was only associated with anal fin length. Furthermore, first dorsal fin length was positively correlated with swim speed, while anal fin length was negatively associated with speed. Our study shows that multiple male signals that are used independently during male competition and female choice also differ in their associated costs. This provides a mechanism for understanding why locomotor costs for exaggerated male ornamentation are not often empirically demonstrated.

Cooperation Improves Success during Intergroup Competition: An Analysis Using Data from Professional Soccer Tournaments.

The benefit mutually gained by cooperators is considered the ultimate explanation for why cooperation evolved among non-relatives. During intergroup competition, cooperative behaviours within groups that provide a competitive edge over their opposition should be favoured by selection, particularly in lethal human warfare. Aside from forming larger groups, three other ways that individuals within a group can cooperate to improve their chances of gaining a mutual benefit are: (i) greater networking, (ii) contributing more effort, and (iii) dividing labour. Greater cooperation is expected to increase the chances of gaining a group benefit by improving proficiency in the tasks critical to success-yet empirical tests of this prediction using real-world cases are absent. In this study, we used data derived from 12 international and professional soccer competitions to test the predictions that: 1) greater levels of cooperative behaviour are associated with winning group contests, 2) the three forms of cooperation differ in relative importance for winning matches, 3) competition and tournament-type affect the levels of cooperation and shooting proficiency in matches, and 4) greater levels of networking behaviour are associated with increased proficiency in the most critical task linked with winning success in soccer-shooting at goal. Winners were best predicted by higher shooting proficiency, followed by greater frequencies of networking interactions within a team but unexpectedly, fewer networking partners and less division of labour. Although significant variation was detected across competitions and tournament-types, greater levels of networking behaviour were consistently associated with increased proficiency in shooting at goal, which in turn was linked with winning success. This study empirically supports the idea that intergroup competition can favour cooperation among non-relatives.

Receivers limit the prevalence of deception in humans: evidence from diving behaviour in soccer players.

Deception remains a hotly debated topic in evolutionary and behavioural research. Our understanding of what impedes or facilitates the use and detection of deceptive signals in humans is still largely limited to studies of verbal deception under laboratory conditions. Recent theoretical models of non-human behaviour have suggested that the potential outcome for deceivers and the ability of receivers to discriminate signals can effectively maintain their honesty. In this paper, we empirically test these predictions in a real-world case of human deception, simulation in soccer. In support of theoretical predictions in signalling theory, we show that cost-free deceit by soccer players decreases as the potential outcome for the signaller becomes more costly. We further show that the ability of receivers (referees) to detect deceptive signals may limit the prevalence of deception by soccer players. Our study provides empirical support to recent theoretical models in signalling theory, and identifies conditions that may facilitate human deception and hinder its detection.