有时当我们去动物园看黑猩猩时，它们会朝你扔便便。这些智能动物怎么会这样？新近的研究发现，投掷粪便等物品是高度组织化的行为。优秀的黑猩猩投射手左半脑发育程度更高，而人类语言组织能力主要发生在左半脑，这看起来并非偶然。
有时猿或者猴子会 朝动物园的游客扔粪便 ，游客们一定会好奇，这些所谓的智能动物怎么会经常玩这种愚蠢的游戏。但是，观察扔便便行为的研究员们却得出了这么一个结论：投掷粪便或者任何其他物品实际上是一种高度组织化的行为。美国埃默里大学比尔.霍普金斯（Bill Hopkins）和同事们正在研究投掷行为的整个流程和它对大脑的影响，相关研究结果已经发表在了《皇家学会哲学汇刊B辑》（Philosophical Transactions of the Royal Society B）上。
霍普金斯和团队人员将研究重心放在了黑猩猩身上，据他们解释，选择黑猩猩主要是因为它是我们的近亲并且它是除人类以外惟一一个会经常瞄准目标投掷物品的物 种。团队人员已经对黑猩猩的行为进行了数年的观察，他们对黑猩猩的脑部进行了扫描，以期找出那些经常扔东西的与那些不频繁扔东西的黑猩猩之间有无关联，且这些行为背后是否有更深层次的含义。
令人吃惊的是，他们发现那些经常投掷物品且精准度高的黑猩猩，其皮质运动区的发育程度更高，且皮质运动区与布罗卡区（Broca's area，这是与人类语言能力相关的重要脑区）的联系更多。换句话说，优秀的黑猩猩投射手的左半脑发育程度更高，而人们语言组织能力主要发生在左半脑，这看起来并非偶然。
于是研究团队猜想，投掷物品的能力或许是人类进化出语言能力的前身。在发现大脑的部分区域可能与黑猩猩的投掷能力有关后，研究人员对黑猩猩们进行了测试，他们发现优秀的投射猩猩在群落中同样也是良好的传播通信者，这又为他们的结论添上了一笔论据。
有趣的是，研究人员还发现，那些投掷能力好的黑猩猩的体力并不优于其他同类。研究人员认为，这可能意味着投掷并不是捕猎的进化，反之，它是群落中交流的一种形式。向他人投掷物品是一种自我表达的方式，这对那些被动物园中的猩猩扔便便的游客们来说或许是显而易见的。
The neural and cognitive correlates of aimed throwing in chimpanzees: a magnetic resonance image and behavioural study on a unique form of social tool use
William D. Hopkins, Jamie L. Russell, Jennifer A. Schaeffer
It has been hypothesized that neurological adaptations associated with evolutionary selection for throwing may have served as a precursor for the emergence of language and speech in early hominins. Although there are reports of individual differences in aimed throwing in wild and captive apes, to date there has not been a single study that has examined the potential neuroanatomical correlates of this very unique tool-use behaviour in non-human primates. In this study, we examined whether differences in the ratio of white (WM) to grey matter (GM) were evident in the homologue to Broca's area as well as the motor-hand area of the precentral gyrus (termed the KNOB) in chimpanzees that reliably throw compared with those that do not. We found that the proportion of WM in Broca's homologue and the KNOB was significantly higher in subjects that reliably throw compared with those that do not. We further found that asymmetries in WM within both brain regions were larger in the hemisphere contralateral to the chimpanzee's preferred throwing hand. We also found that chimpanzees that reliably throw show significantly better communication abilities than chimpanzees that do not. These results suggest that chimpanzees that have learned to throw have developed greater cortical connectivity between primary motor cortex and the Broca's area homologue. It is suggested that during hominin evolution, after the split between the lines leading to chimpanzees and humans, there was intense selection on increased motor skills associated with throwing and that this potentially formed the foundation for left hemisphere specialization associated with language and speech found in modern humans.
