We all know that parrots can talk. Some people may have even seen elephants, seals, or whales mimicking speech sounds. So why can’t our closest primate relatives speak like us? Our new research suggests they have the right vocal anatomy but not the brainpower to use it.

我们都知道鹦鹉会说话。有些人甚至见过大象、海豹或鲸鱼模仿人类声音。那么为什么我们的灵长类近亲不能像我们一样说话呢?我们的新研究表明,他们拥有解剖学上的发声器官,但是却没有使用这些发声器官的脑力。

Scientists have been interested in understanding this phenomenon for centuries. Some have argued that nonhuman primates didn’t have the right-shaped body parts to make the same sounds as we do, and that human speech evolved after our speech organs changed. But comparative studies have shown that the form and function of the larynx and vocal tract is very similar across most primate species, including humans.

几个世纪以来,科学家们一直对这一现象很感兴趣。有些人认为,非人类灵长类动物没有人类这样合适的身体部位来发声,而且人类的语言是在我们的语言器官改变后进化的。但是比较研究表明,包括人类在内的大多数灵长类动物的喉和声道的形式和功能非常相似。

This suggests that the primate vocal tract is “speech ready” but that most species don’t have the neural control to make the complex sounds that comprise human speech. When reviewing the evidence in 1871, Charles Darwin wrote, “the brain has no doubt been far more important.”

这意味着灵长类动物的声道已经“准备好说话了”,但大多数灵长类动物没有神经控制来发出构成人类语言的复杂声音。查尔斯·达尔文在1871年回顾这些证据时写道:“毫无疑问,大脑的作妖要重要得多。”

Along with Jeroen Smaers from Stony Brook University in New York, I have been investigating the relationship between the number of different calls that each primate species can make and the architecture of their brains. For example, Golden pottos have only ever been recorded using two different sounds, while chimpanzees and bonobos use around 40.

我和纽约州立大学石溪分校的罗恩·斯迈尔共同研究了每种灵长类动物能够发出的不同叫声的数量与它们大脑结构之间的关系。举个例子,我们只记录到金熊猴使用了两种不同的声音,而黑猩猩和倭黑猩猩可以使用大约40种声音。


The results indicate a positive correlation between the relative size of the cortical association areas and the size of the vocal repertoire of primates. In simple terms, primates with bigger cortical association areas tended to make more sounds. But, interestingly, a primate’s vocal repertoire was not lixed to the overall size of its brain, just the relative size of these specific areas.

研究结果表明,灵长类动物大脑皮层联络区的大小与声波曲目的大小呈正相关。简单地说,大脑皮层联络区越大的灵长类动物往往能发出更多的声音。但有趣的是,灵长类动物的声波曲目与大脑的整体大小无关,而与这些特定区域的相对大小有关。

We also found that apes have particularly large cortical association areas, as well as a bigger hypoglossal nucleus than other primates. The hypoglossal nucleus is associated with the cranial nerve that controls the muscles of the tongue. This suggests that our closest primate relatives may have finer and more voluntary control over their tongues than other primate species.

我们还发现类人猿的大脑皮层联络区异乎寻常的大,舌下核也比其他灵长类动物大。舌下核与控制舌头肌肉的脑神经相连。这表明,与其他灵长类物种相比,与我们亲缘关系最近的灵长类物种可能更擅长自主地控制舌头。

By understanding the nature of the relationship between vocal complexity and brain architecture, we hope to identify some of the key elements that underlie the evolution of complex vocal communication in our ancestors, ultimately leading to speech.

通过研究声音的复杂性和大脑结构之间关系的本质,我们希望确定一些关键因素,这些因素是我们祖先利用复杂的声音交流并最终进化为语言的基础。