Some time after Homo sapiens were on the scene 200,000 years ago, explained Loh, there was a second explosion — a cultural explosion. And the trigger was the development of language. We don’t know exactly when and where human language first appeared, but language, like DNA, was the vehicle by which information could be passed from one generation to another.

With the discovery of DNA, biologists began to understand how life on Earth, which began as single-celled organisms 3.9 billion years ago, evolved into the stunning diversity of species on the planet today. Around 540 million years ago, for example, favorable climate and atmospheric conditions led to the Cambrian Explosion, where scientists believe the genetic components came together to jump-start the evolution of multicellular life.

The answer, Jones decided, was that they must have branched off from some even more ancient tongue, which he called Proto-Indo-European. Jones and others created the first “family tree” of all the languages that diverged and re-converged from that original language — last spoken an estimated 9,000 years ago — including seemingly unrelated languages like Russian, Hindi, Spanish, Swedish, and English.

“Which completely blew his mind, because he could think of no reason why there should be,” said Loh.

The reason Darwin was so knowledgeable about the evolution of language, Loh told Seeker, was that a century before Darwin and others were arguing that all species evolved from common ancestors, linguists like William Jones were doing the same thing with language. Jones, an 18th-century British judge in India, spoke more than a dozen languages and took an interest in Ancient Sanskrit, which he discovered had striking similarities to Greek and Latin.

"The formation of different languages and of distinct species, and the proofs that both have been developed through a gradual process, are curiously parallel," Charles Darwin wrote in The Descent of Man. "Dominant languages and dialects spread widely, and lead to the gradual extinction of other tongues. A language, like a species, when once extinct, never, as Sir C. Lyell remarks, reappears."

Jonathan Loh is an honorary research fellow at the University of Kent and the co-author, with Dave Harmon, of a 2014 report for the World Wildlife Fund called “Biocultural Diversity: Threatened Species, Threatened Languages.” Loh and Harmon define biocultural diversity as the sum of evolutionary processes that have produced distinctive species of plants and animals, as well as distinctive cultures and languages. Thanks to shifts in human activity, all are under threat.

It’s not an accident that linguists have borrowed terms from biology to classify languages as vulnerable, endangered, or extinct. As many ethnobiologists and conservationists have come to understand, nature and culture are both products of evolution, and many of the same forces that threaten biological diversity also endanger linguistic diversity.

The rate of language loss has reached such a breakneck pace that some scholars predict we’ll lose 90 percent of the world’s languages in the next century, akin to a linguistic mass extinction event.

There are more than 7,000 languages on Earth, yet half of the world’s 7.6 billion people speak just 24 of them and 95 percent speak just 400 of them. That leaves five percent of the global population spread across 6,600 different languages, hundreds of them now spoken by less than ten people.

The regions of the world with the greatest biological diversity are also the ones with the most languages.

This is where biological evolution and cultural evolution show their fascinating similarities. In natural selection, the gene is the basic currency. If a gene inherited from two parents offers a competitive advantage, it’s more likely to be passed on to the next generation. Biological diversity is powered by constant genetic mutations, which, if advantageous, can branch off into new species.

The evolution of culture, according to influential thinkers like Richard Dawkins and Daniel Dennett, has its own currency: the meme. A meme is unit of a cultural knowledge — like a song, story, recipe, art, or style of dress — that can be passed along primarily through the use of language. Memes, like genes, mutate as they pass from one brain to the next, if these mutated memes gain traction, they may evolve into new cultures and languages.

Interestingly, the regions of the world with the greatest biological diversity are also the ones with the most languages. In general, language diversity follows Rapaport’s Rule, which states that species density is highest at the equator and thins out as you move north and south toward the poles. And there are also distinct “hotspots” of biocultural diversity across the Amazon Basin, Central Africa, and the Indonesia/Malaysia region, home to the undisputed champion of linguistic diversity: New Guinea.

Of the 7,000 languages in the world, 1,000 of them are spoken exclusively in New Guinea. With a population of less than 12 million, that means that 14 percent of the world’s languages are spoken by 0.14 percent of global population.

One of the theories explaining why linguistic diversity blossoms in the tropics is that lots of rivers and mountains divide the landscape, isolating small pockets of people. As Darwin found on the Galapagos Islands, geographic isolation allows for distinct traits to evolve out of the same species. That may help explain the language diversity in New Guinea, said Loh, which is carved up by rivers and mountains, and where tribes are not only isolated, but often hostile to outsiders.

The chief difference between biological and linguistic evolution is the speed of change.

“Biological evolution takes place over millions of years. Languages and cultures evolve incredibly fast by comparison,” said Loh. “If you go back in English to Chaucer, who died only 600 years ago, it’s really hard to read and understand his English. Within 25 generations, that ability to understand has gone, because the language has changed so much.”

RELATED: Lost Villages of the Amazon May Have Housed Up to 1 Million Before Colonization

Because the rate of change is so fast, languages can also go extinct much faster than biological species. An estimated six percent of global human languages have gone extinct since 1970, for example, while only one percent each of mammal, bird, and amphibian species have disappeared in that same time span.

The main driver of language endangerment and extinction is a process called language shift, when speakers switch from a native, typically indigenous tongue to the dominant national language. John Sullivant, a language data curator with the Archive of the Indigenous Languages of Latin America, told Seeker that language shift happens for a variety of reasons, but is largely driven by the level of contact with the national culture and the marginalization of indigenous communities.

“In Mexico,” Sullivant said, “nearly every indigenous group is in very close contact with Spanish. And that large amount of contact and the ability to move outside of the community — or having to move outside of the community for various reasons — makes the transmission of the language from parents to children that much more precarious.”

It’s clear that economic forces threaten both biological diversity and linguistic diversity. Members of economically marginalized indigenous communities often migrate to bigger cities or even other countries to support their families, shifting to the dominant language for work. Similarly, the globalization of manufacturing increases the plundering of natural resources, which drives habitat loss, one of the main ways that endangered species go extinct.

What’s doubly troubling is that when a language dies out, so does a wealth of knowledge about native plants and animals, exactly the type of information that conservationists need to protect critical species. Some conservation biologists estimate that indigenous communities, which cluster in regions with the greatest natural biodiversity, are the stewards of 99 percent of the world’s genetic diversity.

Richard Stepp is an ethnobiologist at the University of Florida who has conducted fieldwork among indigenous Mayan communities in Mexico, Belize, and Guatemala.

“In some of these cultures, the single largest category of nouns are plant names. They may have thousands of plant names,” Stepp told Seeker. “So the biodiversity is intimately linked to the language.”

Languages, like species, deserve to be preserved for their own sake, but there are also more utilitarian reasons to want to preserve the knowledge encoded in indigenous languages. For example, only a fraction of the world’s plants have been exhaustively studied for their medicinal properties, but it’s very likely that indigenous cultures have cumutively tested just about everything.

“For a lot of these cultures, their primary healthcare is what they find growing around their house,” said Stepp. “In order to know what’s on the shelf of that living pharmacy, you have to have the language.”

Loh believes that more linguists working with indigenous communities need to receive basic training in biology and botany so that they can capture the depth of the scientific knowledge encoded in endangered languages before they disappear. Stepp said that he brings along specialists for that very reason.

“I’ve seen instances where 5-year-old kids know more plants than adult Westerners. They can easily name 150 plant species,” Stepp said. “This knowledge is gained at a really early age, and not only allows them to survive, but to live a very rich life through the knowledge of food plants.”

RELATED: Neanderthals Painted the World’s Oldest Cave Art

As for preventing the mass extinction that some linguists have foretold, that will be difficult. Many of the remaining speakers of the world’s least-spoken languages are in the 70s and 80s, and the languages will most certainly die with them. Still, as shown by a few high-profile language revitalization efforts, where there’s a strong desire from the people to save a language, and the political support to back it, it’s possible to bring a language back from the brink.

The Hawaiian language, for example, was banned in Hawaiian schools in 1896 and nearly went extinct by the mid-20th century. But “Hawaiian Pride” movements of the 1960s and 1970s brought renewed interest in indigenous culture, and Hawaiian was named one of the state’s official languages in 1978. Today there are elementary schools where the entire curriculum is taught in Hawaiian.

Interestingly, part of the success of language revitalization efforts in Hawaii and elsewhere is making explicit connections between language, culture, and the natural world.

“One of the main ways they’re teaching children Hawaiian is by connecting it with plants, especially food plants,” said Stepp. “I’ve seen the same with Cherokee speakers in the US. The way you make the language relevant is you take them out and forage wild plants for dinner. All of a sudden, they see the connection between who they are as a people, the language that they want to speak, and the environment around them.”