The next time a dog looks up at you with those big, soppy eyes and your heart begins to melt, be aware: you are being manipulated by 33,000 years of evolution.

That is the conclusion of a new scientific study which argues that the raised eyebrows so beloved of owners are more of a survival strategy than an expression of friendship.

The clues, its authors argue, lie in a comparison with wolves, which dogs began evolving from after they were first domesticated by Stone Age man.

Anatomical analysis reveals that while modern dogs have developed small muscles around the eyes which allows them to raise their inner eyebrows, wolves possess hardly any comparable muscles.

Such a stark diversion in what in evolutionary terms is a short period of time has led the researchers to believe that humans naturally favour canines able to look at them with big “puppy dog” eyes, giving them a selection advantage.

Their findings complement previous studies which suggest that big eyes trigger a caregiving response in humans because it reminds them of babies.

Scientists already know that dogs’ ability to read human behaviour and emotion is almost unique within the animal kingdom, and there is growing evidence that eye contact is crucial to this.