Through a study on Australian birds, a team of researchers have lent support to the idea that our big human brain evolved because it is a sexually attractive organ, not just a useful one.
According to the above theory, signs of intelligence - such as creating art, music, and humour - could have made the brainiest people luckiest in love.
The theory was hugely discussed in the book 'The Mating Mind' by an evolutionary psychologist, Geoffrey Miller, almost a decade ago.
Jason Keagy, of the University of Maryland in the US, said that testing the theory in humans was very difficult, and thus he chose to observe satin bowerbirds at Wallaby Creek in NSW instead.
He claimed that Bowerbirds are intelligent.
''But they're not as complex as humans," Stuff.co.nz quoted him as saying.
Keagy could get an accurate record of the male birds' sexual success by videotaping their every movement.
''They can't really lie to us," he said.
Known for their fascination with blue objects, bowerbirds have a strong aversion to red.
In the first IQ test, the researchers placed three red objects under a clear plastic container in their bower, and found that the smartest males could remove the cover and carry away the offending objects in 20 seconds.
''It looks pretty simple, but some weren't able to do it,'' said Keagy.
In a second braintwister, he glued a red object down and observed that some bowerbirds kept on trying in vain to pull it out, while the brighter ones quickly twigged this was impossible and covered it with leaves.
The males who failed the plastic container test were spurned.
''No females were mating with them,'' said Keagy.
However, the smartest birds attracted up to 20 female partners a season.
''This is the first evidence [in any species] that individuals with better problem-solving abilities are more sexually attractive,'' he said.
He claimed that greater intelligence could allow male bowerbirds to woo more females because they can build more elaborate bowers, are better dancers or are more responsive to subtle cues from the females during courtship.
Alternative theories to the mating mind include that our large brain evolved because it was advantageous for hunting or living in social groups, and cultural creativity was simply a fortuitous by-product of the struggle to survive.
The study has been published in the journal Animal Behaviour.