Frans de Waal, professor of primate behavior at Emory University, Georgia, US recently said that even after two centuries of birth of Charles Darwin, there is yet no evolutionary explanation for why humans blush. According to him, blushing is the biggest gap in evolutionary theory.

"We're the only primate that (blushes) in response to embarrassing situations (shame) or when caught in a lie (guilt) and one wonders why we needed such an obvious signal to communicate these self-conscious feelings. Blushing interferes with the unscrupulous manipulation of others," he wrote in the New Scientist.

Some of the world's leading evolutionary biologists were asked by the magazine to recognize the biggest gaps remaining in Darwin's theory to mark the bicentenary of the scientist's birth.

It was confirmed by more than one that evolutionary explanation for the origin of life itself has still not been found.