Hypothesis:\u00a0 The ability to speak human language is a by-product of becoming bipedal, while understanding human language precedes the ability to speak it.<\/p>\n

Evidence:<\/p>\n

Kanzi, a bonobo, understands English and can communicate in English via ‘speaking’ lexagrams<\/a>.\u00a0 However, he cannot speak English, although he can make a variety of communicative sounds such as pant-hoots.<\/p>\n

Human 9-month-old babies understand what is said to them.\u00a0 They can discriminate the sounds of different languages at 6 months<\/a>.\u00a0 However, they cannot speak, although they can make a variety of communicative sounds such as da-da, ba-ba, ma-ma.<\/p>\n

Kanzi’s form of locomotion is quadrupedal knuckle-walking.<\/p>\n

A human baby’s form of locomotion is crawling\/creeping on all fours.<\/p>\n

A chimp\/bonobo’s larynx is positioned high in the throat, allowing it to breathe and drink at the same time.<\/p>\n

A human baby’s larynx is positioned high in the throat, allowing it to breathe and drink\/nurse at the same time.<\/p>\n

An adult human’s larynx is positioned lower in the throat: trying to drink and breathe at the same time leads to choking\/coughing.<\/p>\n

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A chimp\/bonobo and a human infant are incapable of speaking as adult humans do.<\/p>\n

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However, by the time a human infant becomes a full-time biped at about 18 months – 2 years of age, the larynx has dropped into the adult human position, and the toddler can now speak.<\/p>\n

Based on fossil evidence, human ancestors became bipeds at least 4.5 million years ago (mya).<\/p>\n

Deductions:<\/p>\n

It can be deduced that, as part of the evolutionary process of becoming bipedal, the larynx dropped into its current position in adults around 4.5 mya.<\/p>\n

Does this mean that Ardi spoke as we do?\u00a0 Probably not, since her brain was still close to chimp size.<\/p>\n

However, by 2 mya, early Homo<\/em>, such as the Turkana boy, had a brain size in the low end of the normal range in modern humans.\u00a0 Based on archaeological evidence, he also had a much more sophisticated material and behavioral culture.<\/p>\n

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Therefore, it can be deduced that by 2 mya, if not earlier, our ancestors had complex, rich, and sophisticated language and language skills.<\/p>\n

Conclusion:<\/p>\n

Our ability to speak is a by-product of becoming bipeds.\u00a0 Language is not a relatively recent development.\u00a0 We have been speaking sophisticated languages for millions of years.<\/p>\n

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