From ScienceDaily:
Highly mobile eyebrows that can be used to express a wide range of subtle emotions may have played a crucial role in human survival, new research from the University of York suggests.
Like the antlers on a stag, a pronounced brow ridge was a permanent signal of dominance and aggression in our early ancestors, which modern humans traded in for a smooth forehead with more visible, hairy eyebrows capable of a greater range of movement.
Mobile eyebrows gave us the communication skills to establish large, social networks; in particular to express more nuanced emotions such as recognition and sympathy, allowing for greater understanding and cooperation between people.
The study contributes to a long-running academic debate about why other hominins, including our immediate ancestors, had gigantic brow ridges while anatomically modern humans evolved flatter foreheads. Paper. (paywall) – Ricardo Miguel Godinho, Penny Spikins & Paul O’Higgins. Supraorbital morphology and social dynamics in human evolution. Nature Ecology and Evolution, 2018 DOI: 10.1038/s41559-018-0528-0 More.
This is the usual “may have” nonsense, of course. The problem is that any life form may happen to have expressive eyebrows or whiskers.
Or tails. Cats have highly expressive tails. But they have nothing much to say. A huge increase in tail expressiveness would make no difference. Nothing more would be processed.
If these authors were arguing for a non-material thesis of the human mind, their claims might be worth considering. Minds instantiated need to express themselves and eyebrows can be useful. But first, there must be something to say. How does that happen?
See also: The human mind