The study of embryology, also known as embryos, is a key element of evolution in biology and can identify the commonalities and differences between different species. The embryo of an organism refers to the fertilized egg that it progresses through the stages of development, which are unique to the particular species.

In examining how the animal grows from embryo into an adult it is possible to look at the development processes of other species to discover the evolutionary affinities. Many embryos are alike in their initial stages however, as they grow the differences between species are more apparent.

The embryos of species that share an ancestry that is closer to one another are more likely to look alike for longer periods of time because they have a more recent common ancestral. Therefore, embryology is often used to support an evolutionary model, as well as the spread of species from an ancestor with a common origin.

Advent of Evolutionary Embryology

Darwin’s theory on evolution initially restructured embryology in a comparative way and recognized that the resemblance of embryos to other animals could be an argument strongly in support of the genetic connections of various animal species. Darwin also observed that embryonic organisms can make designs that aren’t appropriate for their adult forms, but they do show their resemblance to other species.

He also pointed out the presence eye-like structures in moles that are embryonic pelvic rudiments found in embryonic snakes, as well as teeth in baleen whales that are embryonic. Darwin added that the adaptations that differ from what is considered to be “type” and allow an organism to thrive in its specific environment, develop after the embryo’s development. He also noted that the differences between genera’ species get more pronounced as the development continues in the embryo, as predicted by Von Baer’s laws.

This is why Darwin discovered two different ways to view “descent with modification.” One might focus on that common descended by pointing out the embryonic similarities between two or more species of animals. Or, one could highlight the changes by demonstrating how development modified to create structures that allowed animals to adapt to specific circumstances.

Embryonic Homologies

• One of the most significant distinctions that evolutionary embryologists made was the distinction between homology and analogy.
• They both refer to structures appearing be identical.

Homologous structures

• Organs with a fundamental similarity stems from the fact that they are derived from the same ancestral structure.
• For instance, the wing of a bird as well as the human forelimb are identical.
• Furthermore, their parts are also identical.

Analogous structures

• People whose similarities stem from their performance of a similar task instead of origins from an ancestor with a common origin.
• For instance, the wing of a butterfly and wings of a bird’s are similar.
• The two kinds of wings share a purpose (and consequently are both referred to as wings) However, the insect wing and bird wings were not created from an ancestral structure which was altered through evolution into butterfly wings and bird wings.

Embryology and Theory of Evolution

The field of embryology is a proof that organisms share an ancestral lineage (in keeping with theories of evolutionary theory). Theory of Evolution states that not every characteristic of the embryo of an ancestor’s is evident in its descendants. That is why embryos evolve into various species over time. Different characteristics are found in every embryo. When the embryo is fully developed it develops new embryos with similar characteristics.