Humans Are Still Evolving — and There Is Screaming Evidence For it
What our screams say about our evolution…
Mammals frequently scream when embroiled in social conflicts or to signal the presence of predators and other threats. Humans are no exception. Our brains are wired to quickly recognize and respond to fearful screams as a survival mechanism. At least, this is the established view in neuroscience.
A recent study carried out by researchers at the University of Zurich, however, challenges the dominant theory and sheds new light on the possibility of the ongoing evolution of our species.
The study
Researchers asked twelve participants to scream after imagining a scenario, each of which correlated with one of the following six emotions: pleasure, sadness, joy, pain, fear, and anger.
For example, they recorded participants scream as if their national team had just won the World Cup or as if they were being suddenly attacked in a dark alley by a stranger. In addition, they asked them to express a ‘neutral’ scream by shouting nonstop the vowel /a/.
The scientists carried out an acoustic analysis of the screams, along with using machine learning to assess the difference between them. Then, they ordered separate groups of volunteers to classify and distinguish the different scream types.
Surprising results
In the first task, a set of volunteers listened to the recorded screams and had three seconds to categorize them into one of the seven scream types. In the second, a distinct group of volunteers were presented with two screams- one at a time- and were asked to categorize the screams as fast as possible while still trying to make an accurate decision about the type of scream. The third group of volunteers underwent functional magnetic resonance imaging while listening to the screams.
Surprisingly enough, it took longer for participants in the second experiment to complete the task when it involved alarming screams, and those screams were not as easily recognizable as non-alarming ones like joy. In the third experiment too, less-alarming screams elicited more activity in the auditory and frontal brain regions than more alarming ones.
“It took longer for participants to categorize alarming screams, and those screams were not as easily recognizable as non-alarming ones.”
Evolution in progress
The study shows that scream communication and how we understand that vocalization is more diverse in humans, compared with other mammals. It may also suggest something much more important: the ongoing evolution of our species.
For modern-day humans, the ability to faster identify screams of joy and pleasure seems to have become a bigger priority than the recognition of screams associated with alarming situations. As we experience much less life-threatening situations today compared to our ancient ancestors, the need for the instant recognition of an alarming type of scream may have declined. In contrast, the ever-growing complexity of our behaviors, social structures, and norms may have triggered our brain to react faster to non-dangerous signals.
If this fascinating hypothesis proves to be correct, the notion that our species continues to evolve today will gain even more ground. Though the results are limited to the experiments and don’t reflect how humans would respond to screams in the actual world, the rigor of the study methods provides high confidence in the study results.
Epilogue
The latest study from the University of Zurich not only challenges the long-held notion that our brains are wired to instantly recognize fearful screams as a survival mechanism but also provides interesting insights that help us better understand the ongoing evolution of our species’ non-verbal communication.
Relevant Reads
References
S Frühholz et al. Neurocognitive processing efficiency for discriminating human non-alarm rather than alarm scream calls. PLOS Biology. Published online April 13, 2021. doi: 10.1371/journal.pbio.3000751.
