Answer:
It shows their evolutionary history and their possible common ancestor.
Step-by-step explanation:
Similarity of early embryos of different species is a phenomenon observed by many scientist such as Karl von Baer, Charles Darwin and Ernst Haeckel.
Karl von Baer even formulated the law of embryonic development. He explained that there is a certain embryonic form, basic form, which is similar in different species. After this stage (basic form) each species develops independent-there is a branching pattern of further development.
So, according to von Baer development goes " from the most general forms the less general".