We have to start this post with the definition of convergence in biology.
In evolutionary biology, convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.
It is the opposite of divergent evolution, where related species evolve different traits.
On a molecular level, this can happen due to random mutation unrelated to adaptive changes; see long branch attraction. In cultural evolution, convergent evolution is the development of similar cultural adaptations to similar environmental conditions by different peoples with different ancestral cultures. An example of convergent evolution is the similar nature of the flight/wings of insects, birds, pterosaurs, and bats.
All four serve the same function and are similar in structure, but each evolved independently.
Eyes and wings are among the most stunning innovations evolution has created. Remarkably these features have evolved multiple times in different lineages of animals. For instance, the avian ancestors of birds and the mammalian ancestors of bats both evolved wings independently, in an example of convergent evolution. The same happened for the eyes of squid and humans. Exactly how such convergent evolution arises is not always clear.
In a new study, published in Nature Scientific Reports, researchers have found that, despite belonging to completely different lineages, humans and squid evolved through tweaks to the same gene.
Like all organs, the eye is the product of many genes working together. The majority of those genes provide information about how to make part of the eye. For example, one gene provides information to construct a light-sensitive pigment. Another gene provides information to make a lens.
Most of the genes involved in making the eye read like a parts list – this gene makes this, and that gene makes that. But some genes orchestrate the construction of the eye. Rather than providing instructions to make an eye part, these genes provide information about where and when parts need to be constructed and assembled. In keeping with their role in controlling the process of eye formation, these genes are called “master control genes”.
The most important of master control genes implicated in making eyes is called Pax6. The ancestral Pax6 gene probably orchestrated the formation of a very simple eye – merely a collection of light-sensing cells working together to inform a primitive organism of when it was out in the open versus in the dark, or in the shade.
Today the legacy of that early Pax6 gene lives on in an incredible diversity of organisms, from birds and bees, to shellfish and whales, from squid to you and me. This means the Pax6 gene predates the evolutionary diversification of these lineages – during the Cambrian period, some 500m years ago.
I asked Melissa if this was another example of “convergence”, and she said it was. That’s because the gene is present in animals that DO NOT SHARE A COMMON ANCESTOR. In short, this is exactly identical to the case where a computer programmer reuses the same library of functions in two completely different programs. For example, using the Apache CXF web service library to create two completely different REST-like web services with two completely different clients. (Which is what I am doing at work right now!).
This example of convergence makes no sense on naturalistic evolution – you can evolve the same gene so many times in animals with no common ancestry. It screams out design. See the related posts below for more examples of convergence, and remember that the more we know about science, the more difficult the problem becomes for a naturalist.
- Convergence detected in the genetic structure of bats and dolphins
- How biological convergence falsifies Darwinian evolution
- Science Daily reports on genetic convergence in bats and whales
- What kinds of predictions does intelligent design make?
- Is universal common ancestry based on established facts?