Human feet and hands have evolved from ancient fish fins

Vertebrate animals turn to live on the ground instead of just living in the water is a major event of life history on earth.

New discovery: Human limbs evolved from fish fins

For a long time, the evolutionary human story has become a hot topic for paleontologists. However, all of them stop at the level of suspicion because studies and experiments have not been able to prove the similarities in the bodies between humans and fish.

Vertebrate animals turn to live on the ground instead of just living in the water is a major event of life history on Earth. A long study of Spanish scientists has provided evidence that the development of hands and feet occurs through the addition of new DNA elements, which activate special genes. .

"First, and most importantly, this finding helps us understand the power of gene expression changes on our body shape ," said Dr. José Luis Gomez-Skarmeta of Pablo de Olavide University. Junta de Andalucía in Seville, Spain said: "Many genetic diseases are associated with a distortion of organs in our bodies during development. In the case of genes involved in limb formation, their abnormal function is associated with typical diseases such as synpolydactyly, club and foot-genital syndrome, and hand-foot-genital syndrome (roughly translated as Hand-foot-genital syndrome) ".

To understand how the fins may have developed into limbs, researchers led by Dr. Gómez-Skarmeta and his colleagues at the institute, Dr. Fernando Casares added the Hoxd13 gene , a closed gene. Important role in distinguishing parts of the body, into the fins head of a embryo of zebrafish. He was surprised to find this led to the creation of new cartilage tissue and reduced fin tissue - outstanding changes that adapted to the appearance of the development of land animal fauna.

The researchers wondered whether the unusual gene type Hoxd13 controlled factors that could increase Hoxd13 gene expression in the past to cause similar effects in the evolution of the limbs. They turned to studying DNA control factors, which are known to regulate the activation of Hoxd13 in mouse embryos and are not present in fish."We found that in zebrafish, the control factor for Hoxd13 mice has the ability to control gene expression in peripheral profile fins. This result indicates the ability of the molecular organ to control this control factor. It was also present in the last common ancestor of finfish and legs and was proved by traces in zebrafish, ' Dr Casares said.

In addition, a study by scientists from Clemson University (South Carolina, USA) conducted a work to compare the activity of mudskippers (Mudskipper) and the front legs of tiger salamanders ( Tiger salamanders), which can be used for fossil analysis of tetrapods - the term for vertebrate 4-legged animals - is to understand evolution from underwater life to the ground.

The head of this program, Dr. Sandy Kawano, said the reason for the research conducted on tilapia and tiger salamanders is that they both have some similarities with the ancestors of tetrapod species. By analyzing their organs and their movement patterns, Kawano argued that it was possible to partially decipher the movement of tetrapods when migrating from the water to the ground. Kawano and his partner Richard Blob tracked and compared the forces exerted on the front fins of the mudskipper with the front and hind legs of the tiger salamanders as they moved.

The results show that the finfish's fin is subject to more intermediate pressure (between body and ground) than the salamanders. Kawano's group hypothesized that because the pectoral bone in the chest of the fish cannot withstand this impact, it is difficult to adapt to life on land, while in salamanders, body weight is dispersed in 4 limbs so they can move on the ground more gently and easily.

In addition, researchers at Chicago Medical University have discovered similarities in the origin of genetic code in fish fins with human hands . Specifically, when comparing genes in North American spotted fins with the four-legged wrist gene, scientists found incredible similarities. Even when transplanting this fish's genome into the genus of a lab rat, they act as a mouse and a fish.

Dr Neil Shubin and Professor Robert R. Bensley, who carried out the study, said: 'The above analysis clearly shows that humans are derived from aquatic organisms '. Chances are, hundreds of millions of years ago, the fish evolved into four-legged animals then stood up straight with their legs and became human like today. They also said that the previous studies are stuck in the study object because of inaccuracies. At that time, the experts conducted experiments on Teleost, also known as the Class of the real bone fish , the group of fish includes most of the popular fishes today with about 20,000 to 30,000 fish species arranged in about 40 sets.

However, 300 million years ago, the Teleost fish genome doubled during evolution. The result is the formation of many different gene combinations today. Therefore, when compared with genes in human hands, it is almost impossible to find similarities. If the human wrist consists of a series of small articulated bones, the fish fin Teleost spine is straight and has a small round head at the top, called radial . Meanwhile, North American spotted fish do not undergo genome duplication, so they maintain the genetic similarity with the aquatic species.