“The mother tongue of more than three billion people is one of twenty, which are, in order of their current predominance: Mandarin Chinese, Spanish, English, Hindi, Arabic, Portuguese, Bengali, Russian, Japanese, Javanese, German, Wu Chinese, Korean, French, Telugu, Marathi, Turkish, Tamil, Vietnamese, and Urdu. English is the lingua franca of the digital age, and those who use it as a second language may outnumber its native speakers by hundreds of millions. On every continent, people are forsaking their ancestral tongues for the dominant language of their region’s majority. Assimilation confers inarguable benefits, especially as Internet use proliferates and rural youth gravitate to cities. But the loss of languages passed down for millennia, along with their unique arts and cosmologies, may have consequences that won’t be understood until it is too late to reverse them.”