Crucial Feature of Human Language Emerged More Than 135,000 Years Ago

Humans speak more than 7,000 languages today. As different as they all seem, researchers argue in a new review that they all stem from a single linguistic family tree that emerged before our species split into distinct populations 135,000 years ago.

By 100,000 years ago, this verbal revolution was cemented into the behavior of Homo sapiens, archeologically visible in our use of symbolism in body decorations and engravings.

"Every population branching across the globe has human language, and all languages are related," says MIT linguist Shigeru Miyagawa.

"I think we can say with a fair amount of certainty that the first split occurred about 135,000 years ago, so human language capacity must have been present by then, or before."

Engravings on 60,000 year old eggshell suggest humans were using symbolic meanings. (Texier et al, PNAS, 2010).

Miyagawa and colleagues reviewed the scientific literature and found 15 studies that reach the same conclusion in spite of using different methods. Whole-genome, Y chromosome, and mitochondrial DNA analyses all point to Homo sapiens first fracturing into distinct populations around 135,000 years ago.

"Had linguistic capacity developed later, we would expect to find some modern human populations without language, or with some fundamentally different mode of communication," the researchers argue in their paper. "Neither is the case."

A lag between the emergence of human language and its widespread appearance in the archeological records suggests this novel level of communication molded characteristic human behaviors, from the rise of systemic engraving to burials of our dead, the team believes.

Such behaviors have only been located sporadically before then.

Decorative objects, like these 75,000 year old shell beads from Africa, are another example of symbolism. (Henshilwood et al., Science, 2004)

"Somehow it stimulated human thinking and helped create these kinds of behaviors," says Miyagawa. "If we are right, people were learning from each other [due to language] and encouraging innovations of the types we saw 100,000 years ago."

Other archaeologists, however, counter that these behavioral shifts were a more gradual accumulation, aided by – but not necessarily centered around – language as humans experimented with new materials and formed more elaborate social networks over time.

What's more, the capacity for language pre-exists our species and is present in other animals. But evidence for consistent use of symbolic thinking has not been so widespread.

While the way we arrange words to create complex meaning has been detected in other animals, how humans use it appears unique, at least so far, as there's a lot we're still learning about how other animals communicate.

Using words symbolically, as in figurative speech such as 'to spill the beans', is one example of the unique way we use language.

"This gives us the ability to generate very sophisticated thoughts and to communicate them to others," explains Miyagawa, arguing "language was the trigger for modern human behavior."

This research was published in Frontiers in Psychology.