Difference between homology and homoplasy


Homology and homoplasy are the two common scientific terms used in science evolution. Though they sound similar but actually they are different in their scientific meanings. These terms refer to the biological characteristics which are shared by two or more species, hence the prefix homo has been used. One term represents the shared characteristics from any common ancestor, and at the same time, another term refers to shared characteristics that have been evolved independently by each species.

What is homology

Homology refers to any biological structure or any characteristics that are the same in nature. Homological characteristics are found majorly in two or more different species. These characteristics can be traced to any common ancestor. To explain the homology, we can take the example of forelimbs of frogs, birds, and lizards. Though every species has a different limb appearance, even then they all have a similar bone structure. A similar arrangement of bones was identified in fossils of old extinct species. This species name was “Eusthenopteron” and this was inherited by rabbits and frogs.

What is homoplasy?

Homoplasy can be described as biological structure or characteristics which are common between two or more species. These species will not have anything in common and they were not inherited from a common ancestor. A homoplasy will always evolve independently. This is due to the natural selection of a similar environment or because of a similar type of niche. Other species will also have a similar trait.

Comparison of divergent and convergent evolution

The example of divergent evolution is homology. In homology, single ancestor species split or diverge into two or more types of species. The reason behind this type of evolution is natural selection or any environmental isolation.  This kind of isolation separates the new species from its ancestors. In this case, the shared ancestral characteristics are called “homologies

On the other hand, homoplasy is due to convergent evolution. In this type of evolution, different species develop, instead of inheriting similar kind of traits. An example of convergent evolution is when a species evolves with a mimic of the appearance of any other. We can take the example of a scarlet king snake and harmful coral snake; they both represent convergent evolution.

Homology vs. Homoplasy

Homology and homoplasy both have similar physical characteristics and it is often very difficult to identify them. We can take the example of bird and bat wings; both are a great example of homology and homoplasy. The bone structure of the wings is homologous. All the wings include the breast bone, upper arm bone, and forearm bones. This basic bone structure is common in many species like; humans, bats, and birds. Many of them share a common ancestor.

But wings are homoplasies and since many species with this shared bone design do not have the wings, we can take the example of humans. So, all the other divergent species developed fingers and other limbs to survive in their different niche or trait.