It proves that cetacean is not always living in the oceans, which had gone to the ocean from the land on their four legs about 50,000,000 years ago. They get used to the life in the ocean and settle down. Their hind limbs nearly disappear, while the forelimbs evolve into flippers. And what contributed to the appearance of flippers? Recently post-doctoral students Wang Zhe of our School of Life Science, his supervisor and co-work in Britain have provided essential hints to answer this question through their latest findings.
Biologists have found that a gene architectural family called Hox controls the organs of most animals. The development of animals’ forelimbs is usually under the influence of 5’HoxD, in particular, Hoxd12 and Hoxd13. A mutation in those two genes will lead to the deformity of their forelimbs, such as Syndactyl. Through gene knockout experiments can we see that the two genes can adjust the numbers of fingers.
Wang Zhe and other researchers discovered the importance of Hoxd12 and Hoxd13 on the origin and diversification of cetacean flippers by gene sequencing on the two genes in cetacean and other mammals.
In order to test and verify the result, they had analyzed the two genes in various mammals for more than one year. They compared the differences of their gene sequence, and found out that the two Hox genes have an evidently higher evolution speed in cetacean than them in other mammals. And in the end they concluded that Hox genes’ Darwin selection time is completely the same as the macro-evolution times when the cetacean’ flippers came out. It is a result of natural selection, not made by accident.
The lasted research achievement has been published on the internationally authoritative magazine Molecular Biology and Evolution, called “Adaptive evolution of 5’HoxD genes in the origin and diversification of the cetacean flipper”.
