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.
Jonathan Wells explains the problem that convergence poses for naturalistic evolution:
Human designers reuse designs that work well. Life forms also reuse certain structures (the camera eye, for example, appears in humans and octopuses). How well does this evidence support Darwinian evolution? Does it support intelligent design more strongly?
Evolutionary biologists attribute similar biological structures to either common descent or convergence. Structures are said to result from convergence if they evolved independently from distinct lines of organisms. Darwinian explanations of convergence strain credulity because they must account for how trial-and-error tinkering (natural selection acting on random variations) could produce strikingly similar structures in widely different organisms and environments. It’s one thing for evolution to explain similarity by common descent—the same structure is then just carried along in different lineages. It’s another to explain it as the result of blind tinkering that happened to hit on the same structure multiple times. Design proponents attribute such similar structures to common design (just as an engineer may use the same parts in different machines). If human designers frequently reuse successful designs, the designer of nature can surely do the same.
I’m a software engineer, and we re-use components all the time for different programs that have no “common ancestor”. E.g. – I can develop my String function library and use it in my web application and my Eclipse IDE plug-in, and those two Java programs have nothing in common. So you find the same bits in two different programs because I am the developer of both programs. But the two programs don’t extend from a common program that was used for some other purpose – they have no “common ancestor” program.
Now with that in mind, take a look at this recent article from Science Daily, which Mysterious Micah sent me.
The evolution of similar traits in different species, a process known as convergent evolution, is widespread not only at the physical level, but also at the genetic level, according to new research led by scientists at Queen Mary University of London and published in Nature this week.
The scientists investigated the genomic basis for echolocation, one of the most well-known examples of convergent evolution to examine the frequency of the process at a genomic level.
Echolocation is a complex physical trait that involves the production, reception and auditory processing of ultrasonic pulses for detecting unseen obstacles or tracking down prey, and has evolved separately in different groups of bats and cetaceans (including dolphins).
The scientists carried out one of the largest genome-wide surveys of its type to discover the extent to which convergent evolution of a physical feature involves the same genes.
They compared genomic sequences of 22 mammals, including the genomes of bats and dolphins, which independently evolved echolocation, and found genetic signatures consistent with convergence in nearly 200 different genomic regions concentrated in several ‘hearing genes’.
[...]Consistent with an involvement in echolocation, signs of convergence among bats and the bottlenose dolphin were seen in many genes previously implicated in hearing or deafness.
“We had expected to find identical changes in maybe a dozen or so genes but to see nearly 200 is incredible,” explains Dr Joe Parker, from Queen Mary’s School of Biological and Chemical Sciences and first author on the paper.
“We know natural selection is a potent driver of gene sequence evolution, but identifying so many examples where it produces nearly identical results in the genetic sequences of totally unrelated animals is astonishing.”
Nature is the most prestigious peer-reviewed science journal. This is solid material.
There is an earlier article from 2010 in New Scientist that talked about one of the previous genes that matched for hearing capability.
Bats and dolphins trod an identical genetic path to evolve a vital component of the complex sonar systems they use to pursue and catch prey.
The finding is unusual, because although many creatures have independently evolved characteristics such as eyes, tusks or wings, they usually took diverse genetic routes to get there.
Analysis of a specific gene has now demonstrated that although bats live in air and dolphins in water, where sound travels five times faster, they independently evolved a near-identical gene that allows them to accept high-frequency sound in the ear – vital for sonar.
The gene makes prestin, a protein in hair cells of the cochlea, which is the organ in the inner ear where sonar signals are accepted and amplified. Prestin changes shape when exposed to high-frequency sound, and this in turn deforms the fine hair cells, setting off an electrical impulse to the brain. So the protein has the important jobs of detecting and selecting high-frequency sounds for amplification.
When researchers examined the molecular structure of the prestin gene from a range of animals, they found that the variants in echolocating bats and dolphins were virtually indistinguishable.
Indistinguishable genes in animals that don’t share a common ancestor? Maybe a better explanation for the evidence we have is – common designer.