Were penguins always flightless? Theresa Cole and her team argue that penguins could fly at some point, but that they lost that ability more than 60 million years ago as they adapted to marine life. After examining various penguin fossils and genetic information, the researchers concluded that over time penguins developed underwater vision, blood oxygenation, and bone density better suited for swimming than flying. Thus, environmental conditions might have driven penguins to change from flyers to swimmers.