A new brain imaging study has shown evidence that human language might have emerged together with advanced tool making skills. Because we can physically date much of the timeline for tool making, the work indicates that language could have emerged almost two million years ago – far earlier than Homo sapiens.
While the results aren’t definitive, the study demonstrates
- New technologies that monitor brain performance while people perform practical tasks, and
- New methods for dating events that don’t have physical records (like language) by associating them with events that do
Work like this brings neuroscience into the realm of experimental archaeology, offering new approaches to studying the past.
The appearance of language is important because it’s a foundation for symbolic thinking – a critical distinction between humans and other animals. Language is a tool of symbols, essential to conveying meaning and concepts in the absence of physical objects or events. Human knowledge rests on language representations.
Scientists would obviously like to know when and how language arose. Unfortunately, language doesn’t leave real indicators in the long period before writing. Available evidence like the hyoid bone (300,000 years ago) shows the capability for speech, and cave paintings (40,000 years ago) point to symbolic thinking, but this isn’t the same as identifying a starting point for language.
A study published in Science in 2012 showed that tool making and language at least use similar regions of the brain. The researchers also found that the overlap in these regions was greater when more modern – and, therefore, more complex – tool making methods were used. The study employed functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) for brain imaging, systems that measure blood flow in the cortex associated with brain activity. These
systems are large, however, and require a subject to keep very still for good results. Furthermore, the systems were used on different subjects at different times. The correlations found in the study were nevertheless very exciting.
The new research was conducted by scientists at the University of Liverpool in the United Kingdom. This work built upon the earlier study but used functional transcranial Doppler ultrasonography (fTCD), a system that also measures blood flow but is portable. fTCD allows subjects to perform more realistic tasks during brain
The Liverpool researchers employed expert knappers – people skilled in making tools by chipping stone – and imaged their brains while they made tools and while they thought of specific words (that began with a particular letter). The research team found that blood flow changes between the two tasks were most similar in the first 10 seconds, when the knappers were strategizing how to approach their tool making. The association between tasks was similar across all the subjects, but was even more similar within subjects. That is, the brain response of each subject was highly aligned for the two tasks.
The Acheulean tool making technology, which emerged about 1.75 million years ago, was used for the study and the results would seem to show, therefore, that if language and tool use coevolved, then both capabilities would be about this old.
The results aren’t conclusive, of course. Certainly, there are issues with the precision of using blood flow as a measure of brain function. Furthermore, even if the results are accurate, the circuitry for language might have been spurred by tool making skill, but with language itself evolving later.
More work will certainly be done in this area. For now, however, the effect is to extend cognitive research into the “real world,” i.e., performing brain studies in situ. And, the pairing of brain imaging with tasks that represent ancient activities will certainly open up new ways to study the development of human behavior and thinking. Stay tuned to future results of this investigative approach.