Describe how comparing early development can scientists learn about the relatedness of species. give an example!

Talking of early development we are referring to the embryonic stage of development. The closer similarity of their embryos shows a relationship between the organisms. For example an adult chimpanzee and an adult human being look so different and on the other hand their embryos look so much alike.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.