TORONTO -- Babies in the womb have salamander-like hand and feet muscles, according to new imaging analysis.
The muscles, which are typically shed before birth, are commonly found in adult reptiles and amphibians but were lost among humans at least 250 million years ago through evolution, biologists say in the new research published Tuesday in the .
The findings, based on 3D imaging of 15 embryos taken by a team of French scientists two years ago, show 鈥渆volution at play鈥� and contest the myth that humans have become more complex and sophisticated. In fact, we have only simplified, lead author Rui Diogo told CTVNews.ca via phone from Washington, D.C.
鈥淚f you want to make a super-human, you actually would keep these muscles. It would be amazing if we could use all of the digits as we use the thumb. A lizard can do that. But we lost those things,鈥� he said.
The research illuminates patterns of human development, confirming that we begin in a much more generalized way before making deletions. 鈥淔irst you form a generalized tetrapod (four-limb) configuration, and then you begin to lose things and specialize,鈥� he said. The study showed that after seven weeks an embryo has about 30 muscles in the hands and feet, but by about 13 weeks, the embryos shed about one-third of them. 鈥淗umans will lose the muscles going to the other digits and only keep the thumb ones,鈥� he said. 鈥淏ut an animal that uses a tree much more often will keep those muscles or reinforce them, but lose the other ones.鈥�
The findings could have implications for medicine, added Diogo. While the spare muscles are typically lost among humans, when they do remain, they are sometimes linked to deformities. Those defects have been considered severe and random in the past, but the new imaging confirms that the muscles have a basis in the human anatomy.
鈥淚t鈥檚 not random at all,鈥� he said. 鈥淵ou can only have things that are made by evolution in development. It鈥檚 difficult to create something from scratch.鈥�
The new paper is the first time such detailed imaging of embryo muscles has been released, said Diogo, noting that past understandings of embryo development was based on decades old analysis and imaging.
