Fish, amphibians, reptiles, birds, and mammals have similar embryos.

They all start with gill slits. Fish and some amphibians grow to have gills. Some amphibians, reptiles, birds, and mammals develop lungs to breathe air.
They all start with tails. Fish, some amphibians, reptiles, and birds grow tails. Humans do not keep their tails.
Fish and reptiles develop scales. Amphibians, birds, and humans have skin. Birds have feathers, and humans have hair.

With which animal do humans exhibit the most linear relationship

Humans exhibit the most linear relationship with primates, specifically apes and monkeys. This is because humans share a common ancestor with primates and have many anatomical and genetic similarities with them. Additionally, primates also exhibit complex social behaviors and cognitive abilities that are similar to humans.