Tag Archives: Convergence

News

Study: biological convergence found in human and squid eye genes

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Christianity and the progress of science
Christianity and the progress of science

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.

With that being said, here is an article from Real Clear Science with me.

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.

This is an example of convergence because the same gene is present in animals that DO NOT SHARE A RECENT 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. Software engineers re-use libraries all the time in different programs. It makes sense in an software engineering paradigm.

But this example of convergence makes no sense on naturalistic evolution – random mutation and selection does not create the same design in two animals with no common ancestry. It screams out design.

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Polemics

Convergence detected in the genetic structure of bats and dolphins

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Apologetics and the progress of science
Apologetics and the progress of science

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.

Excerpt:

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.

Excerpt:

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.

News

New study: another example of convergence, this time for geomagnetic navigation

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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.

And now, Evolution News has a story about a new discovery.

Turtles have the ability to navigate by sensing magnetic isolines:

Science Magazine gives a brief review of the findings:

Much like shifting sand, magnetic fields slide slightly over time, and their strength also increases as one moves away from the equator, akin to latitude.This property gives each stretch of coast a unique geographic marker, known as an isoline. The team found that in years when these magnetic isolines moved apart, the turtle nests spread out over a larger area — by 1 or 2 kilometers. Conversely, when isolines converged, the nests squeezed into a smaller patch of beach, suggesting the turtles follow shifting magnetic tracks to their favorite nests. The findings also argue that a magnetic address is imprinted on loggerhead turtles at birth to point the way home.

But so do salmon, and other birds, fishes and mammals:

Remarkably, salmon show this same ability. Brothers and Lohman write:

In a previous study, the migratory route of salmon approaching their natal river was shown to vary with subtle changes in the Earth’s field. Whereas the endpoint of the salmon spawning migration was presumably the same regardless of route, our findings demonstrate for the first time a relationship between changes in Earth’s magnetic field and the locations where long-distance migrants return to reproduce.

Joining the contenders for this skill set are more unrelated animal types:

… our results provide the strongest evidence to date that sea turtles find their nesting areas at least in part by navigating to unique magnetic signatures along the coast. In addition, our results are consistent with the hypothesis that turtles accomplish natal homing largely on the basis of magnetic navigation and geomagnetic imprinting. These findings, in combination with recent studies on Pacific salmon, suggest that similar mechanisms might underlie natal homing in diverse long-distance migrants such as fishes, birds, and mammals.

So here we have a highly-precise navigational ability, able to cue on very faint properties in the earth’s magnetic field, then on olfaction, and possibly on “other supplemental local cues” to find home across thousands of miles. The sensory “instruments” involved are integrated so that they are able to coordinate their functions for the same goal. Furthermore, the baby turtles, with their tiny brains, must have the ability to memorize the natal signatures of odors and magnetic field properties at birth, then recall those memories years later as large adults. (Sea turtles return about every two years to lay eggs.)

That would be a conundrum enough to explain by unguided processes like natural selection. But then, adding to the difficulty for Darwinism, similar abilities are found in distantly related animals like fish, birds, and mammals. Even if a Darwinian could show a possible line of descent from fish to mammal, the abilities involved would have been lost and regained multiple times, because not all fish, birds, and mammals use magnetic navigation. Given the complexities of the sensory systems involved, this would represent a case of “convergent evolution” on steroids. If the origin of this capability in one type of animal is highly implausible by mutation and selection, how about four times or more?

A design perspective, by contrast, would expect that unrelated animals on a common planet would share similar capabilities for their needs. The earth’s magnetic field is global. It isn’t surprising that very different animals would be designed to use that feature of the earth.

How can it be that animals that have no recent common ancestor can have evolved this remarkable ability independently? The best explanation of this convergence is common design, not common descent.

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