The discovery helps to explain why human embryos resemble those of animals at the early stages of life.
Embryos for humans and other animals often look alike at certain developmental stages because they share ancient genes.
These ancient genes are expressed during a middle "phylotypic period" of embryonic development for all species.
Developing human, fish and other embryos therefore at times share features, such as tails and gill-like structures.
Human embryos resemble those of many other species because all animals carry very ancient genes. These genes date back to the origin of cells, which are expressed during a middle phase of embryonic development, according to two separate papers published in this week's Nature.
The findings help to explain why our embryos have a tail when they are a few weeks old and why human embryos retain other characteristics, such as fur-like hair and fish embryo similarities, seen in the developmental stages of other species.
"On average, the similarities will be even stronger for more closely related species," Diethard Tautz told Discovery News.