Neurobiological Rewards in the Evolution of Endurance Running in Humans and Cursorial Mammals

自达尔文以来，研究人员一直将两足行走的起源视为人类进化的决定性事件。最近的研究表明，虽然双足行走是早期人类进化的基本要素，但耐力跑（ER）可能在人属的起源中发挥了重要作用。然而，ER假说还没有得到充分的检验，鉴于其对人类进化的可能意义，值得更全面的研究。 这项研究通过研究人类和奔跑的哺乳动物的奔跑神经生物学，提出了一种新的ER假说的测试。 人类跑步者经常报告在跑步比赛期间和之后的神经生物学奖励（通常称为“跑步者的高”），这在他们跑步的动机中起着重要作用，并增加了他们在长距离内维持高有氧强度的能力。 这些神经生物学奖励包括幸福感，欣快感，幸福感，焦虑减少和疼痛感减少，这似乎是由内源性大麻素（eCB）释放到血液和大脑中引起的。 ECBs是内源性化合物，可激活外周和中枢神经系统中的大麻素受体，并导致神经生物学奖励和疼痛减轻。 这是可能的，选择可以产生ER在几个哺乳动物谱系的运动活动与eCB信号，因此，与神经生物学的奖励。 证据的收敛进化的神经生物学奖励ER在人类和其他爬行哺乳动物将有力地支持这一假设，即人类ER的能力是自然选择的产物。这项研究将测试运动诱导的eCB信号在人类和爬行哺乳动物中趋同进化以激励和奖励跑步行为的假设。 将在跑前和跑后测量爬行哺乳动物（人类和犬）和非爬行哺乳动物（小鼠和雪貂）样本的ECB水平。 如果与非游标相比，游标中跑步距离后eCB显著增加，则支持ER假设。 此外，将对人类跑步者进行情绪评估，以检查eCB和神经生物学奖励之间的相关性。这项研究将提供关键的新数据，以验证耐力跑在人类进化中发挥重要作用的假设。 这是第一个研究人类和其他哺乳动物跑步的神经生物学奖励的趋同进化的研究，因此代表了对ER假说的新测试。 如果神经生物学的奖赏在人类和其他哺乳动物的游标中是趋同进化的，那么ER可能在人类进化中发挥了重要作用。 此外，这项研究将对动物迁徙的动机和进化产生重要影响。 此外，这项研究将对人类心理健康障碍产生重要影响。 心理健康社区已经开始为治疗抑郁症、焦虑症和其他心理健康疾病开出运动处方。 运动可以通过内源性大麻素信号传导来缓解抑郁症状，因为这一途径在动物模型中起着抗抑郁作用。 这项研究将提供关键的新信息，关于如何以及为什么运动可以减轻这些疾病的症状。 这项研究还将为亚利桑那大学和加州大学滨江分校的研究生和本科生提供大量培训和研究机会，并将改善亚利桑那大学人类学和药理学系之间的研究基础设施。 最后，该项目将开启亚利桑那大学、德克萨斯大学圣安东尼奥健康科学中心和加州大学滨江分校之间的新合作。

Ever since Darwin, researchers have viewed the origins of bipedal walking as a defining event in human evolution. Recent research suggests that, while bipedal walking was an essential element of early hominin evolution, endurance running (ER) may have played an important role in the origins of the genus Homo. However, the ER hypothesis has not been fully tested and, given its possible significance for human evolution, deserves a more complete examination. This study presents a novel test of the ER hypothesis by examining the neurobiology of running in humans and running mammals. Human runners often report neurobiological rewards during and after running bouts (frequently termed the "Runner's High") that play a major role in both their motivation to run, and increase their ability to sustain high aerobic intensities over long distances. These neurobiological rewards include feelings of happiness, euphoria, well-being, anxiety reduction, and reduced pain sensation, which appear to be caused by the release of endocannabinoids (eCBs) into the bloodstream and brain. ECBs are endogenous compounds that activate cannabinoid receptors in both the peripheral and central nervous systems and lead to neurobiological rewards and pain reduction. It is possible that selection could have generated ER in several mammalian lineages by linking locomotor activities with eCB signaling and therefore, with neurobiological rewards. Evidence of the convergent evolution of neurobiological rewards for ER in humans and other cursorial mammals would strongly support the hypothesis that human ER capabilities are the products of natural selection. This study will test the hypothesis that exercise-induced eCB signaling evolved convergently in humans and cursorial mammals to motivate and reward running behaviors. ECB levels will be measured before and after running in a sample of cursorial mammals (humans and dogs) and non-cursorial mammals (mice and ferrets). The ER hypothesis will be supported if eCBs increase significantly after distance running in cursors compared to non-cursors. In addition, mood assessments will be given to human runners to examine the correlation between eCBs and neurobiological rewards.This study will provide critical new data testing the hypothesis that endurance running played an important role in human evolution. This is the first study to examine the convergent evolution of neurobiological rewards for running in humans and other mammals and thus, represents a novel test of the ER hypothesis. If neurobiological rewards evolved convergently in humans and other mammalian cursors, then ER likely played an important role in human evolution. Additionally, this study will have important implications for the motivation and evolution of animal migration. Additionally, this study will have important implications for human mental health disorders. The mental health community has begun prescribing exercise to treat depression, anxiety, and other mental health disorders. Exercise may relieve depressive symptoms through endocannabinoid signaling since this pathway acts as an anti-depressant in animal models. This study will provide critical new information regarding how and why exercise may alleviate symptoms of these disorders. This study will also provide numerous training and research opportunities for graduate and undergraduate students at the University of Arizona and UC Riverside and will improve research infrastructure between the Departments of Anthropology and Pharmacology at the University of Arizona. Finally, this project will open new collaborations between the University of Arizona, University of Texas Health Science Center, San Antonio, and University of California at Riverside.