A famous quote every biologist in the world agrees with: "Nothing in biology makes sense except in the light of evolution."
From Evolution is True by Jerry Coyne:
"Creationists often cite Haeckel's 'fudged' drawings as a tool for attacking evolution in general: evolutionists, they claim, will distort the facts to support a misguided Darwinism. But the Haeckel story is not so simple. Haeckel may not have been guilty of malfeasance, but only of sloppiness: his "fraud" consisted solely of illustrating three different embryos using the same woodcut. When called to account, he admitted the error and corrected it. There's simply no evidence that he consciously distorted the appearance of embryos to make them look more similar than they already were."
"The blood vessels of embryonic humans start out resembling those of embryonic fish, with a top and bottom vessel connectedly by parallel vessels, one on each side ('aortic arches'). In fish, these side vessels carry blood to and from the gills. Embryonic and adult fish have six pairs of arches; this is the basic ground plan that appears at the beginning of development of all vertebrates. In the human embryo, the first, second, and fifth arches form briefly at the beginning of development, but disappear by four weeks of age, when the third, fourth, and sixth arches have rearranged themselves, looking much like the embryonic vessels of a reptile. In the final adult configuration, the vessels are rearranged still more, with some having vanished or transformed themselves into different vessels. The aortic arches of fish undergo no such transformation."
"All vertebrates begin development looking like embryonic fish because we all descended from a fishlike ancestor with a fishlike embryo. We see strange contortions and disappearances of organs, blood vessels, and gill slits because descendants still carry the genes and developmental programs of ancestors. And the sequence of development changes also make sense: at one stage of development mammals have an embryonic circulatory system like that of reptiles; but we don't see the converse situation. Why? Because mammals descended from early reptiles and not vice versa."
https://answers.yahoo.com/question/index?qid=20151029111235AARjSaC&sort=N
