今天扑腾着翅膀的鸟类是在距今1.5亿年之前由小型恐龙进化而来的。已知最早的鸟类已经拥有和现代鸟类相似的翅膀和羽毛。不过有一个问题研究者们一直争论不休:最早的鸟类比如始祖鸟,有没有能力扇动双翼持续飞翔,还是只能滑翔或者干脆就是从树梢飘到地面呢? Birds fluttering today are evolved from small dinosaurs 150 million years ago. The earliest known birds already have wings and feathers similar to those of modern birds. However, there is a problem researchers have been endless arguments: the earliest birds, such as Archeopteryx, have the ability to flap continuous flying wings, or can only glide or simply float from the treetops to the ground?