Step-by-step explanation:
As it happens, early human embryos do have slits in their necks that look like gills. This is almost certainly because humans and fish share some DNA and a common ancestor, not because we go though a “fish stage” when in our mothers' wombs as part of our development towards biological perfection
Ancestral characters are often, but not always, preserved in an organism’s development. For example, both chick and human embryos go through a stage where they have slits and arches in their necks like the gill slits and gill arches of fish. These structures are not gills and do not develop into gills in chicks and humans, but the fact that they are so similar to gill structures in fish at this point in development supports the idea that chicks and humans share a common ancestor with fish. Thus, developmental characters, along with other lines of evidence, can be used for constructing phylogenies.