Darwin, Darwinism & Evolution / Natural Selection

eburacum

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To hasten the process, you may favour mutations through a bombardment of X rays, and witness "evolution in action". But that starts to get dangerous ! I wouldn't try this at home !
Atomic gardening is a technique used to encourage mutations using a radiation source.
This relatively crude method has had some useful results, especially in peppermint and grapefruit.
https://en.wikipedia.org/wiki/Atomic_gardening
 

Mythopoeika

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Atomic gardening is a technique used to encourage mutations using a radiation source.
This relatively crude method has had some useful results, especially in peppermint and grapefruit.
https://en.wikipedia.org/wiki/Atomic_gardening
I used to work at a place that had been a research establishment owned by Fisons.
At one end of the estate, there were some greenhouses left untouched. There were radioactivity signs everywhere.
They'd been doing a bit of this, using fissile material to spark off mutations.
It was a bit worrying that Fisons had never taken this away when they sold the place.
 

EnolaGaia

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The classic Darwinian answer has long been based on your second point - eyes represent a net disadvantage because they are surface features vulnerable to damage or infection.

More recent research results demonstrate that viable eyes continue to grow / develop during the organism's lifetime, and the cumulative metabolic / energy requirement for their maintenance and use is substantial.

Even more recent research seems to indicate some of the trade-offs pertain to the genetic and deep biochemical aspects of the organism. The seemingly eyeless Mexican blind cave fish actually begins developing eyes but this development stops and regresses owing to certain genetic / protein factors peculiar to the blind cave-dwelling version of this fish (as opposed to its sighted river-dwelling version). Some of the pathways involved in triggering eye regression are the same ones involved in enhancing chemo-receptors (e.g., taste buds).

Another factor that isn't often mentioned is that cave-dwelling species are typically small isolated populations. This fosters a high degree of inbreeding and accelerates the proliferation and persistence of locally novel genetic mutations regardless of selection effects per se.

This 2017 research paper provides a good overview of the multi-faceted situation based on research into the Mexican blind cave fish:

Krishnan, J., & Rohner, N. (2017).
Cavefish and the basis for eye loss.
Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 372(1713), 20150487.
https://doi.org/10.1098/rstb.2015.0487

FULL TEXT (and PDF access): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5182419/
 

Mikefule

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Evolution. The bacteria thing you mentioned, they must have already had that potency to start with otherwise they'd all be dead, if that's the right word. (Somehow 'dead bacteria' doesn't sound right.)

@kesavaross The theory of evolution by natural selection is not perfect (although, like all scientific theories, it is evolving) but it is demonstrably true in general terms because it is an ongoing process. We can find evidence of evolution in, amongst other things:
  • Tracing the various stages of evolution of prehistoric species through similarities and differences in fossils from different dates.
  • DNA analysis of present populations, and ancient remains that have been well enough preserved.
  • Observation of what happens to populations of a known species when its environment changes.
  • Topically: evidence of how a virus develops variants, some of which flourish more successfully than others.

We can also apply basic maths to the theory. Any genetic characteristic that increases the probability of an organism successfully reaching breeding age, breeding, and raising its young, will inevitably be more likely to remain in the population than a genetic characteristic that decreases the probability of these things happening. Over time, that genetic characteristic will become prevalent.

We can also identify and describe specific mechanisms that are part of evolution, we can observe them operating, and we can even tinker with them with reasonably predictable outcomes. Every species of farm animal, every breed of working dog, or show dog (etc.) is the result of selective breeding. In these cases, the farmer or dog enthusiast is the aspect of the environment which selects one set of genetic traits over another.

I acknowledge that there are gaps in the theory, not least that it does not explain adequately how life arose in the first place. However, it is a good theory, well supported by evidence, and is continually being refined in the light of new evidence.
 
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Tunn11

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Thanks EnolaGaia :hoff:
 

Mikefule

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Excellent response from @EnolaGaia . Thank you.

Evolution is a mathematical process, not an intelligent one. On the basis of probabilities, evolution "selects in" things that aid reproduction, and it "selects out" things that hamper reproduction.

In a lightless cave, eyes no longer aid a creature in reaching sexual maturity, breeding, and successfully raising its young. There is no probability pressure in favour of eyes.

Eyes are complex, and require a substantial energy budget to grow and maintain. They are also vulnerable to injury or infection. In a closed cave system, where the energy supply is limited, wasting energy on growing and maintaining eyes reduces a creature's chance of reaching sexual maturity, breeding, and successfully raising its young. The probability pressure is therefore in the direction of no eyes.

In a small closed population, the rate of change will be greater because a small number of mutant genes is less diluted.
 

Coal

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Excellent response from @EnolaGaia . Thank you.

Evolution is a mathematical process, not an intelligent one. On the basis of probabilities, evolution "selects in" things that aid reproduction, and it "selects out" things that hamper reproduction.

In a lightless cave, eyes no longer aid a creature in reaching sexual maturity, breeding, and successfully raising its young. There is no probability pressure in favour of eyes.

Eyes are complex, and require a substantial energy budget to grow and maintain. They are also vulnerable to injury or infection. In a closed cave system, where the energy supply is limited, wasting energy on growing and maintaining eyes reduces a creature's chance of reaching sexual maturity, breeding, and successfully raising its young. The probability pressure is therefore in the direction of no eyes.

In a small closed population, the rate of change will be greater because a small number of mutant genes is less diluted.
I've been involved in small fishery management for some years and it's not unusual to occasionally come across fish born without eyes in the general population of some breeds, for example tench. Such tench are usually black (not green) and there is just a layer of skin across the eye socket.
 
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