Convergent Evolution — Definition & Examples

What Is Convergent Evolution?

Convergent evolution is when two (or more) distantly related species independently evolve the same trait or gain a similar function. In math terms, convergence is when two things get really close to each other.

For example, bats, birds, and insects are very distantly related but all have evolved the ability to fly. In this case, you would say that these groups have converged in their evolution, independently gaining the same function over time. This type of evolution is often the result of species occupying similar niches (ecological roles). Over long periods of time, the species will experience a lot of the same environmental factors, which means that they experience similar selective pressures.

Here's an example:

Anoles are a family of lizard closely related to iguanas. There are many species of anole, found mainly in the Caribbean islands. What's so cool about anoles is that on every island they are found, they have separately evolved into six distinct forms, also called ecomorphs. These ecomorphs occupy a specific niche within each island.

This is convergent evolution because the same forms independently evolved to fill the same niches multiple times on different islands.

This type of evolution is different from what people typically are referring to when they talk about evolution. Usually when people talk about evolution they mean speciation. This is when one species adapts over time and splits off, forming new (closely related) species. This type of evolutionary development can be called divergent evolution since the species are diverging in different directions.

Example of Convergent Evolution

Convergent evolution is the independent evolution of similar trait(s) in unrelated species. This usually happens because the species are living in similar (or the same) environments, so they evolve similar adaptations to face the same selective pressures.

Notice how all of these organisms have similar body forms. They are all adapted for life underwater, where being able to move with minimal resistance is an advantage. But they don't all have this trait because of shared common ancestry. In fact, they are all in totally different biological classes. Even sharks and dolphins, which may seem similar, come from very different backgrounds.

This is convergent evolution because these unrelated species have separately evolved similar adaptions to the same niche.

Independently Developing Similar Traits

You might have noticed that many unrelated species around the world have similar features. This is caused by convergent evolution.

This form of evolution happens when two or more species which do not have a recent common ancestor occupy similar niches in different parts of the world. This causes the different species to face very similar pressures of natural selection.

Over time, each species will develop adaptations that help it survive and reproduce in its niche. These adaptations end up being similar even though they developed independently.

(Video) Convergent Evolution vs. Divergent Evolution: Shared Traits Explained

by 2 Minute Classroom

This quick video explains the differences between convergent and divergent evolution.

Coming from Different Places

Both birds and bugs have wings to fly, but birds and bugs are very distantly related. There are plenty of organisms between birds and bugs that don’t have wings and don’t fly. So, how did both of these groups end up with similar features? Enter convergence.

Convergent evolution is an evolutionary pattern that happens when distant relatives in the tree of life develop similar features or behaviors.

What Makes Organisms “Distant Relatives”?

All living things are related, so what’s so special about two different organisms evolving the same adaptations? What makes convergent evolution an interesting pattern is that it is distant relatives that develop the same adaptation. When biologists talk about groups of living things being distantly related, they mean the two groups split off from their most recent common ancestor a long, long time ago. Like, on the scale of a million years ago. Since then, the two groups have been evolving independently, and through those courses of independent evolution, somehow each group developed some similar feature.

If you look at a tree of life, a graph that biologists like to use when looking at taxonomy, you’ll see that the arthropods (bugs) and the chordates (birds, vertebrates, and a few other animals) split off from one another a very long time ago. Lots of creatures between them don’t have wings, yet both birds and bugs do have wings.

Analogous Structures

In the example we’ve been using, wings are an analogous structure. If you know what the word “analogy” means, you’ll understand what an analogous structure is. An analogy is a comparison of two things that aren't really alike. For example, you might say that the surface of Mars is like the desert or that learning biology is like learning to ride a bike (you never forget it).

So, what are analogous structures then? They are physical features of organisms that have the same or similar structures but different origins. In other words, they’re physical structures that evolve through convergence. Both bugs and birds adapted to have wings so that they could fly.

How Does Convergence Happen?

Like all forms of evolution, convergence happens as a result of natural selection. As genetic variations lead to new physical traits or behaviors in a species, some of the new features or behaviors help certain individuals survive and reproduce. The more fit individuals reproduce, and the species changes as more and more members look like those fit individuals because their genes were passed down to new species’ members. Evolution has occurred.

What’s special about convergent evolution is that the same structures or behaviors are selected for in different species. This usually happens because those species fill similar niches in their communities or live in similar parts of their habitats. If we’re talking about birds and bugs, these animals have a shared habitat: the air. Without wings, neither animal could live, eat, or reproduce in their high-up home.

Other Patterns of Evolution

There are two other types of evolution: parallel evolution and divergent evolution.

Parallel and convergent evolution are similar in that the two species involved evolve independently, but in parallel evolution, they don’t completely deviate from each other at any point. In this kind of evolution, the two species share some trait in their relatively recent history (maybe like a similar body plan). Basically, the two species that developed in parallel are just as similar to each other as their more recent ancestors were to one another. An example is two plants that have both evolved thick stems to survive dry desert climates.

Divergent evolution happens when species branch off from a common ancestor and develop different traits. This pattern of evolution happens when organisms have to fit into different, unrelated niches or habitats. An example of this is adaptive radiation. In this type of evolution, we see homologous structures. These are traits with the same basic structure but are used in different ways. They are derived from a common ancestor.