High-res 3D images of human embryos reveal a wide range of muscles that have been “present in our ancestors; however, usually absent in the adult human.” Like, there are hand muscles that temporarily seem in human embryos; however, they usually disappear before birth. Based on the researchers, our human ancestors lost these “muscles from the back of the hand around 250 million years ago as mammals and reptiles separate from the evolutionary tree.”
These are appearing and disappearing, or atavistic, muscles are pieces of evolution, said by biologist Rui Diogo. Such atavistic muscles are built as a base from which to begin paring down to the final set of muscles that persons are born with, he says. “Losing and specializing, that’s what occurs in human evolution.”
Different animals have kept some of these muscles. Adult chimpanzees and human embryos have epitrochleoanconeus muscles in their forearms; however, most adult people don’t. Human’s mammalian ancestors additionally misplaced dorsometacarpales muscles from the back of the hand about 250 million years ago as mammals and reptiles split on the evolutionary tree. Lizards still have these muscles, and they usually seem in human embryos, however then are misplaced or fuse with different muscles during growth and aren’t present in most adults.