Oct 04, 2019 08:00:00

In the developing fetus, it turned out that `` the muscular possessed by the lizard '' is temporarily generated

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It is also known that humans are animals that have been born through a long evolution, and there are remnants of organs that have lost their roles in the process of evolution . Researchers at Howard University in the United States discovered that human fetuses disappear temporarily before they are born, although 'muscles that exist in lizards' are temporarily generated.

Development of human limb muscles based on whole-mount immunostaining and the links between ontogeny and evolution | Development
https://dev.biologists.org/content/146/20/dev180349

Tiny 'Lizard-Like' Muscles Found in Developing Embryos Vanish Before Birth | Live Science
https://www.livescience.com/disappearing-muscles-human-embryo.html

Human Fetuses Develop Lizard-Like Body Parts That Disappear Before Birth
https://gizmodo.com/human-fetuses-develop-lizard-like-body-parts-that-disap-1838679203

The research team of Howard University evolutionary biologists

Rui Diogo and others is a 3D scan database of human embryos and fetuses created by Alain Chédotal and others, neurologist and developmental biologist at the University of Paris 6 in France. Was analyzed. As a result, it was found that the undeveloped muscles were generated in the limbs in the developing fetus in the womb.

Diogo's team analyzed detailed limb muscles early in development using images of fetuses from 7 to 13 weeks of gestation. According to the research team, the limbs of fetuses around the 7th week of pregnancy contained about 30 muscles each, but the number decreased to 20 at the 13th week of pregnancy after 6 weeks.

For example, the research team pointed out that muscles called 'dorsometacarpales' are developed in the hands of fetuses around the 10th week of pregnancy. The following image shows the dorsal metacarpal muscle, which is found in lizards and salamanders. However, in humans, the dorsal metacarpal muscle fuses with other muscles or contracts and disappears before birth.

The ancestors of reptiles and mammals have the same ancestry, but Diogo pointed out that the dorsal metacarpal muscle has not developed in humans more than 250 million years ago. In this way, several examples of remnants of organs that have deteriorated during evolution have been discovered, humans have left muscles that move their ears, and the fetus at the 4th week of pregnancy has a tail. It has also been confirmed.

Most of the muscles that disappeared in the middle of development seemed to have fused and contracted with other muscles at the seventh week of pregnancy, but some muscles remained until around the 11th week of pregnancy. “The evolutionary remnants that appear during the development of the fetus are surprisingly late,” Diogo said.

According to the research team, there are cases where the muscles that should have disappeared in the fetus are rarely left until adulthood. The remaining muscles are not noticed in most cases, and instead of causing no problems, they do not have the advantage of smoother limb movements than others. It seems that there are many people with

Down's syndrome and Edwards syndrome among those who have such muscles, and the research team says that slowing or stopping development in the uterus may cause muscles that should originally disappear to remain thinking about.

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Mr. Diogo will continue to study how human heads, arteries, and nerves develop in the uterus using the fetal 3D scan database. Clarifying the developmental process of the fetus not only understands the evolutionary history of mankind in detail, but may also help medical professionals to predict the structure beneath the skin, Diogo said Suggested.