American scientists managed to find out when the ancestors of four-legged animals appeared – about 390 million years ago. The study authors note that this happened very quickly.
Scientists know surprisingly little about how and when the fish grew legs and made their way to land. This is believed to have happened somewhere between the Middle and Late Devonian (400 to 360 Ma ago).
In a new study published in the journal Nature Ecology and Evolution, scientists have determined the most accurate time frame for the first appearance of legs in fish. The researchers also found that the development of the anatomy of the ancestors of tetrapods slowly progressed due to their excellent adaptation to life in the water. But, after these animals came out on land, anatomical development accelerated significantly, which is associated with the need to adapt to new environmental conditions.
During the study, scientists used mathematical modeling to estimate the rate of evolution of the legs and combined it with data from fossil footprints and bodies. The experts concluded that the bones of the skull and jaws were the fastest to improve. This was due to the need to find food for survival. After that, the limbs underwent the same rapid changes, which is also associated with adaptation and the need for survival.
The team of researchers also found that the bipedal “cousins” of tetrapods evolved very slowly, and their anatomical structures were stable and practically unchanged. However, tetrapods grew legs very quickly after an evolutionary split.