Mammals share a common evolutionary ancestry with fish. During embryonic development, regardless of whether it’s a human, aardvark, or zebra, the mammalian embryo initially exhibits fish-like characteristics such as gill slits and a tail. However, as development progresses, the embryo gradually transforms into a fetus that resembles its specific mammalian species, resembling its parents.

As a result, the organs of mammals are homologous to those of fish. This includes the eyes, brain, skin, limbs, mouths, tongues, senses of smell and taste, as well as the organs involved in sexual reproduction. Additionally, the overall body layout of mammals follows a similar pattern found in fish, with a head at one end, a central tube running along the body beneath the spine, and an anus at the posterior end. The internal organs, including the heart and others, also share comparable structures.

In fact, it is possible to teach basic human anatomy using a fish as a model. In the past, I have engaged grammar school children in this approach by dissecting a fish and using it to demonstrate anatomical concepts. Sometimes, I would offer them the choice to participate in the dissection instead, sparking their curiosity and engagement in learning.