Discovered "disappearing muscles" in humans more than 250 million years ago

Some human muscles that “disappeared” more than 250 million years ago have been found not in exercise enthusiasts but in embryos within the first few months.

The team captured the peculiarity by using new technology that creates high-resolution 3D images of the embryo and fetus during the first trimester of pregnancy.

They found that at 7 weeks gestation (when the fetus is the size of a blueberry), there are about 30 muscles in the hand. By week 13 (the size of a lemon), 10 of them are fused and the number of muscles drops to 20. Some of them even disappear during the transition from reptilian to reptile-like traits. mammal.

Discovered "disappearing muscles" in humans more than 250 million years ago

“Previously, we understood much more about the early development of fish, frogs, chickens and mice than we did in humans, but these new techniques allow us to see human development in much greater detail.

What’s even more fascinating is that we have observed different muscles that have never been described in human prenatal development, and some of these muscles have been seen even in young adults. At 11.5 weeks of gestation, it is very late for meiosis to develop,” said Dr. Rui Diogo, from Howard University.

The team says they were able to capture a detailed timeline of the appearance of these muscles, as well as their separation, fusion or loss during embryonic growth and development.

The fused muscles, known as the limb muscles, were formed during early human development. It provides an interesting look at evolution. We often find ourselves getting more and more complicated, but some anatomical features streamline and become simpler.

“It’s actually a story about anatomical simplification. Mostly muscle is lost, bone is lost. An adult human has, in fact, less muscle and bone in the body than an adult rat. or an adult lizard,” said Dr.