Bat is a small animal that can often be seen in the night sky of cities. They belong to the order Chiroptera of mammals, with more than 1,000 species in total. They feed on insects, but there are also those that catch fish, suck blood, or eat fruit. Bats are distributed in most regions of the world and are the only mammals that have conquered the blue sky. But how did they fly into the sky?
Fossils are the best evidence. The earliest known bat fossils date back to the Eocene about 55 million years ago, when the pterosaurs that dominated the sky had already become extinct. Bats could freely forage and survive in the blue sky at that time. However, these fossils are very similar to the present-day form of bats, and no earlier bat fossils have been found so far. What did the ancestors of bats look like, and how did they evolve? These remain mysteries.
However, there are clues. Based on the skeletal characteristics of bats, it can be inferred that their wings evolved from their forelimbs. The upper arms, forearms, metacarpals, and phalanges are particularly long, and they are connected by a thin and tough membrane that extends to the sides of the body, hind limbs, and tails, forming a unique wing membrane system. The wing of bats is strikingly similar to that of pterosaurs, which once dominated the sky in the Mesozoic era and have now become extinct. To fly into the blue sky, two different creatures - mammalian bats and reptilian pterosaurs - adopted the same evolutionary strategy.
Scientists believe that mastering the ability to fly was not an overnight achievement. The ancestors of bats likely lived in trees. To escape predators or catch flying insects, they sometimes needed to quickly move from one tree to another. Over the course of long-term adaptation and evolution, individuals with membranes on their forelimbs that helped them glide in the air gained more survival opportunities. The result of natural selection allowed these advantageous traits to be inherited and strengthened over generations, eventually transforming them and conquering the blue sky.
Of course, bats not only changed their physical structure, but their cells also evolved. Scientific research shows that the energy required for flight is 3 to 15 times that required for walking on the ground. Therefore, to fly, they need stronger power. In biological cells, there is a special structure responsible for supplying energy - mitochondria. In 2010, molecular zoologists Academician Zhang Yaping and Dr. Shen Yongyi found that the mitochondria of bats have become increasingly powerful during evolution, indicating that their cellular energy systems have also been upgraded. With this "inside-out" comprehensive evolution, it's no surprise that bats could fly into the sky.
Although many bats have quite high flying skills, compared with modern masters of the blue sky - birds, their flying level is still far behind. Therefore, in the evolutionary process, bats tried to avoid direct competition with birds as much as possible. Most of them simply chose to hunt at night when there are fewer birds active, and hide during the day. This staggered outing of bats is precisely the great wisdom that has enabled them to survive to this day.