Tag Archives: Design

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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

Target acquisition and interception in dragonflies

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

Here is a fascinating post about some of the capabilities of dragonflies from Evolution News.

Selective attention

First, dragonflies have “selective attention” – the ability to focus on a single prey and ignore other distractions:

Dragonflies are among the best flyers in the insect world. Their twin pairs of paper-thin wings allow them to hover and move in all directions, even in mating. When the time comes to dart after prey at high speed, they rarely miss.

What’s their secret? One is “selective attention” — a trait previously known only in primates, according to new research from the University of Adelaide, Australia. Selective attention is the ability to focus on one object and exclude others. Just as a tennis player must focus on the ball and ignore the cheers of the crowd, a dragonfly must pick out one target from a swarm of insects and avoid being distracted by all the others.

Here’s a snip from the research paper:

Our data make a compelling case that CSTMD1 reflects competitive selection of one target. We emphasize “competitive,” because the attended target is not always the same between trials or even within a trial, as seen in strikingly perfect switches from one to the other…. Competition is further suggested by rare examples where the activity observed under Pair stimulation initially lags both T1and T2 responses… suggesting initial conflict in the underlying neural network before resolution of competition by a “winning” target.

We previously showed that CSTMD1 still responds robustly to a target even when it is embedded within a high-contrast natural scene containing numerous potential distracters. Taken together with recent evidence that the behavioral state of insects strongly modulates responses of neurons involved in visuomotor control, our new data thus suggest a hitherto unexpected sophistication in higher-order control of insect visual processing, akin to selective attention in primates.Perhaps the most remarkable feature of our data is that once the response “locks” onto a target (or following a switch), the second target exerts no influence on the neuron’s response: the distracter is ignored completely.

In order to succeed at the task of catching its prey, the dragonfly has to tune out all other distractions.

Target selection

In addition, dragonflies have the ability to intercept a target in mid-air – similar missile defense systems on AEGIS cruisers and destroyers.

The Evolution News article explains:

Another paper on dragonflies shows that these marvels of the insect world are equipped with navigational equipment that can do vector calculus. In the Proceedings of the National Academy of Sciences, Gonzalez-Bellido and a team at the Howard Hughes Medical Institute discerned “Eight pairs of descending visual neurons in the dragonfly [that] give wing motor centers accurate population vector of prey direction.”

Intercepting a moving object requires prediction of its future location. This complex task has been solved by dragonflies, who intercept their prey in midair with a 95% success rate. In this study, we show that a group of 16 neurons, called target-selective descending neurons (TSDNs), code a population vector that reflects the direction of the target with high accuracy and reliability across 360°. The TSDN spatial (receptive field) and temporal (latency) properties matched the area of the retina where the prey is focused and the reaction time, respectively, during predatory flights. The directional tuning curves and morphological traits (3D tracings) for each TSDN type were consistent among animals, but spike rates were not. Our results emphasize that a successful neural circuit for target tracking and interception can be achieved with few neurons and that in dragonflies this information is relayed from the brain to the wing motor centers in population vector form.

What did I make of this? Well, evidence like this always causes me to think aboutthe reality of God, and the disturbing thought that we do not live in an accidental universe where I can do whatever I want and be accountable to no one. It’s easier to believe that – it requires less work and it frees us to be our own boss and make our happiness the first priority. As individuals, it’s very tempting for us to think that we are number one, and to resent our obligations to anyone else. The problem is that the scientific data doesn’t support that worldview. The facts are what they are and it is up to us, now, to try to find out who the designer is and what he wants from us.

News

Biomimetics again: scientists reverse engineer the design of snake scales

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

Today, I have an example of biomimetics.

But first, here’s what that is:

Biomimetic refers to human-made processes, substances, devices, or systems that imitate nature. The art and science of designing and building biomimetic apparatus is called biomimetics, and is of special interest to researchers in nanotechnology, robotics, artificial intelligence (AI), the medical industry, and the military.

This is from Science Daily. (H/T Fuz Rana)

It says:

A snake moves without legs by the scales on its belly gripping the ground. It generates friction at the points needed to move forwards only and prevents its scales from being worn off by too much friction. Researchers of KIT have found a way to transfer this feature to components of movable systems. In this way, durability of hip prostheses, computer hard disks or smartphones might be enhanced.

“Friction and wear are two of the biggest challenges in systems of several individual components,” Christian Greiner of the Institute for Applied Materials says. A solution is found in nature: Snakes, such as the ball python, or lizards, such as the sandfish skink, use friction to move forwards, but can reduce it to a minimum thanks to their scales. Together with Michael Schäfer, Greiner developed a process to transfer the scale structure of reptiles to components of electromechanical systems: With a fiber laser, they milled scales into a steel bolt of 8 mm in diameter.

With the help of two different structures, the materials researchers tested whether the distance of the scales influences friction behavior. In the first structure, the scales overlap and are located very closely to each other, such as the scales on the belly of a ball python. The second structure consists of scales arranged in vertical rows at a larger distance, such as the skin of a sandfish skink. “The distance between the rows in our experiment was the smallest possible distance we could produce with the laser. The structure, hence, does not entirely correspond to that of the sandfish skink,” Greiner says. In the future, however, the researchers plan to produce structures that are closer to the original in nature.

[…]To find out whether scales reduce friction, Greiner and Schäfer fixed the structured surface of the bolts to a rotating plate. The experiments were carried out without and with a lubricant (1 ml of mineral oil). For the experiments with oil as lubricant, the scientists used steel disks. Under dry sliding conditions, sapphire disks were applied. The disk diameter was 50 mm.

Experiments under lubricated conditions revealed that both narrow and wide arrangements of the scales increase friction compared to the unstructured bolt: By the wide scales, friction is increased by a factor of 1.6. The narrow scales increase friction by a factor of 3. In the non-lubricated state, the wide scale structure reduced friction by more than 40 percent, while friction was reduced by 22 percent in case of a narrow scale structure.

The finding that the narrow scale structure increases friction under both lubricated and non-lubricated conditions had not been expected by the researchers: “We assumed that the narrow structure is more effective, as it is closer to nature,” Greiner says.

See the related posts for more examples of humans learning from the engineering designs in nature.

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