Contrary to popular belief, the transformation of simple basic hips as in fish to more complex weight-bearing hips was a relatively simple evolutionary process, say scientists .
Previously scientists believed that the evolution from basic hips as in fish to more complex weight- bearing hips as in walking animals was the result of a series of complicated processes. However, researchers from Monash University, MacQuarie University and Uppsala University found that this process was rather simple.
The first time four-legged animals or Tetrapods set foot on land was about 395 million years ago and this migration from water to land was not an easy task. Tetrapods needed to develop a strong hip bone that could carry the weight of the body as well as have it connected through the spine via an ilium, which was not present in the fish ancestors of Tetrapods.
Dr Catherine Boisvert of the Australian Regenerative Medicine Institute at Monash University, MacQuarie University's Professor Jean Joss and Professor Per Ahlberg of Uppsala University presented a study that was published in the journal "Evolution and Development." The study found that this transformation was not as complex as previously believed as some of the other key elements required to build a strong hip bone were already present in the fish ancestors of Tetrapods.
The study was conducted on Australian lung fish and the Axolotl, commonly known as the Mexican Walking Fish, where researchers studied its hip development. They found that the basic fish hips could be transformed into complex weight-bearing hips in a few evolutionary steps.
"Many of the muscles thought to be "new" in tetrapods evolved from muscles already present in lungfish. We also found evidence of a new, more simple path by which skeletal structures would have evolved," Dr Boisvert said in a press statement
According to researchers, the sitting bone is actually an extension of the pubis which already existed in fish. An iliac process that fish already possessed resulted in the connection to the vertebral column.
The transition from ocean-dwelling to land-dwelling animals was a major event in the evolution of terrestrial animals, including humans, and an altered hip was an essential enabling step," Dr Boisvert said. "Our research shows that what initially appeared to be a large change in morphology could be done with relatively few developmental steps."
