Ostriches and penguins are familiar to most people. Ostriches are the largest existing birds, mainly living on the African continent. Their robust bodies, strong legs, slender necks, and small heads have left a deep impression on us. Penguins are mainly distributed in the Southern Hemisphere and are marine birds. Penguins have a round body and waddle around when walking, which is very cute. Although ostriches and penguins don't look alike in appearance, they share one common feature: they can't fly. Why can't ostriches and penguins fly? Fossil research shows that ostriches, penguins, kiwis, emus, and other birds evolved into flightless birds between about 65 million and 34 million years ago, which is the result of birds' long-term adaptation to the environment.
African ostriches are representatives of ground-dwelling birds. Their ancestors lived in the grasslands and deserts of Africa, where food was scarce, so ostriches needed to spend a lot of time foraging. Their legs became stronger, and their claws with only two toes were more suitable for running, which gave large ostriches a better chance of survival against predators on the grasslands. However, their huge size made flying difficult and impossible, and their wings became redundant and gradually degenerated. Ostriches that lost the ability to fly can weigh up to 115 kilograms.
Penguins are mainly distributed in Antarctica and sub-Antarctic regions, and their main food is fish and shrimp in the sea. To withstand the cold, their bodies store a large amount of fat and become elliptical and streamlined, which is not conducive to flying but very suitable for diving and fishing. Penguins' wings have also degenerated into strong flippers due to the loss of their flight function, allowing them to swim quickly in the water.