A recent study showed that the human hands and feet have the same genetic program with the gills on some types of fish such as sharks and stingrays.
The results of this study then revive a 138 years old theory, which says that the human limbs initially evolved from the gills of fish. The theory was first expressed in 1879 by a German anatomy expert, Karl Gegenbaur. He said, that the fish fin and even human limbs evolved from a structure of cartilage in the gills of fish.
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| Fish fins and limbs in mammals may have an evolutionary link to the gill arches of cartilaginous fish such as sharks, skates and rays. The link comes down to a gene called "Sonic hedgehog." (Picture from: http://adf.ly/1ZigPW) |
Indeed, unlike other fish, the fish with cartilaginous skeleton such as sharks and stingrays have a series of skin folds to protect their gills. These folds formed by some arch cartilage.
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| A skate embyro examined in the study to prove the Sonic gene. (Picture from: http://adf.ly/1ZihHh) |
For about 100 years the Gegenbaur theory did not get much response, because at least the fossil record supports this theory. Now scientists are re-thinking the Gegenbaur while using cutting-edge genetic research techniques. This time in a study they examined the stingray embryos.
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| Researchers have used the latest genetic techniques on embryos of the little skate and found striking similarities between the genetic mechanism used in the development of its gill arches (shown above) and those in human limbs. (Picture from: http://adf.ly/1ZigPW) |
The results were startling, because they found similarities in the genetic mechanisms of the gills growth on fish embryos with the growth of human limbs. The similarities of mechanism was found in a gene called "Sonic Hedgehog". This gene is very important in the growth of the hands and feet of humans. It serves to determine the identity of each human finger and keep the bones growth of hands and feet.
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| The new study shows the functions of the Sonic hedgehog gene in human limb development - dictating the identity of each finger and maintaining growth of the limb skeleton - are mirrored in the development of the branchial rays in skate embryos. A stock image of a model of a human arm is shown above. (Picture from: http://adf.ly/1ZigPW) |
This mechanism was also discovered by scientists in the growth of stingrays embryo. The study was led by Andrew Gillis of the University of Cambridge, UK, and has been published in the Development journal on April 18, 2016. *** [EKA | FROM VARIOUS SOURCES | DAILYMAIL]
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