Our past is embedded in the words we speak, and the stories we tell and sometimes write down. Yet UNESCO estimates that, if nothing changes, half of the 6,000 tongues spoken on the planet today will be gone by the end of this century, and with them, embedded history.

A language is considered nearly extinct when only a few native speakers use it and it’s no longer being taught to children, which means, if nothing changes, they are doomed to disappear. Unlike trees, whose genes can be conserved in seed banks, or animals that can be bred in captivity, language is so intangible it can only survive if people speak it.

While extinction is a natural phenomenon, just as it is in nature, colonization, globalization and urbanization have significantly sped up the process. “Of course it’s all right that we don’t speak Latin in the streets of Rome anymore, but before it disappeared, Latin had a chance to leave descendants,” explains Wade Davis, a cultural anthropologist and explorer-in-residence at the National Geographic Society, who says today’s rate of language loss is unprecedented.

UNESCO’s Atlas of the World’s Languages in Danger lists 576 as critically endangered, with thousands of others labeled as endangered or vulnerable. No continent is immune to this phenomenon and some are down to only a handful of speakers. Like Ainu, a Japanese dialect from the island of Hokkaido that only has about 10 native speakers left. Or Brazilian native’s Apiaká who might only have a single speaker left. Others are thought dormant, with no known speakers but no confirmed extinction either, like the Baygo language in South Sudan. The U.S. is home to many languages in a similar situation. In 2014 alone, the last known monolingual speakers of Chickasaw and Klallam, two Native American languages, died.

Preservationists are fighting back in some places. In New Zealand, for example, the Maori have opened nursery schools where elders conduct classes, all in Maori. They call them “language nests.” In Mexico, after refusing to talk to each other for years, the last two surviving speakers of Ayapaneco — a thousand-year-old pre-Columbian tongue — recently reunited to try and save their language. And several organizations like the Living Tongues Institute for Endangered Languages or National Geographic are going to great lengths to document and record languages at the brink of disappearance. Even Google is putting its resources at the service of safeguarding linguistic diversity through its Endangered Languages Project.

It can easily be argued that a language’s extinction is just a form of ethno-linguistic natural selection. But when a language dies, the world loses much more than just words and syntax. “Only a few cultures erected grandiose architectural monuments by which we can remember their achievements. But all cultures encode their genius in their languages, stories and lexicons,” says K. David Harrison, director of research at the Living Tongues Institute and author of When Languages Die.

Of course, measuring the value of language is impossible, but that might be precisely why preserving it is so crucial. We might not understand the value of what we had, even after it’s gone.