Animal facial anatomy: explaining the evolution of puppy dog eyes

An image to illustrate puppy dog eyes
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New research on animal facial anatomy has explained the evolution of ‘puppy dog eyes’ as a means of communication with humans.

The research from the University of Portsmouth analysed the function of ‘puppy dog eyes’ and suggests that the facial anatomy of dogs and wolves has evolved over thousands of years to allow them to express desires to humans.

The evolution of puppy dog eyes

Co-author of the paper and lead anatomist at Duquesne University, Pittsburgh, USA, Professor Anne Burrows, said: “To determine whether this eyebrow movement is a result of evolution, we compared the facial anatomy and behaviour of these two species and found the muscle that allows for the eyebrow raise in dogs was, in wolves, a scant, irregular cluster of fibres.”

How humans unconscious preferences influence selection

The research team of behavioural and anatomical experts in the UK and USA was led by comparative psychologist Dr Juliane Kaminski. Kaminski explained: “The findings suggest that expressive eyebrows in dogs may be a result of humans unconscious preferences that influenced selection during domestication. When dogs make the movement, it seems to elicit a strong desire in humans to look after them. This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the ‘puppy dog eyes’ trait for future generations.”

Co-author and anatomist Adam Hartstone-Rose, at North Carolina State University, USA, expressed how important facial expressions are for social interaction, despite the subtlety of facial anatomy. Hartstone-Rose added: “These muscles are so thin that you can literally see through them – and yet the movement that they allow seems to have such a powerful effect that it appears to have been under substantial evolutionary pressure. It is really remarkable that these simple differences in facial expression may have helped define the relationship between early dogs and humans.”

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