Random Mutation and Natural Selection – An Example

Posted by on August 8, 2010 in Thoughts | 5 comments

In biology, most random mutations take place on a level that is either unnoticeable or of a nature as to be trivial to a species. Many evolutionary naysayers claim that evolution is false because of their lack of understanding of what mutations are, and how they could possibly be of any benefit to the plant or animal to which it occurs. They tend to see mutations like they happened in the X-Men comic book, granting special powers to the mutant, or like the Elephant Man, rendering the mutant disfigured and deformed. And there are some who even claim that mutations do not exist at all. And because most mutations happen gradually over time, and humans are blinkered to only truly understand timeframes as they relate to a human lifespan, most mutations are imperceptible to the average person, and occur unnoticed.

Enter the picture Acacia Leprosa.

Acacia Leprosa - Scarlet Blaze

Acacia Leprosa - Scarlet Blaze

I love late winter in Melbourne, the garden seems to come back to life after the winter dormancy. It’s still cold, but it’s mild enough that we would probably only get the occasional frost, and snow is almost unheard of in these parts. And at this time of year, all the trees start to bloom and blossom.

The above photo was taken in my back yard yesterday afternoon. It is of Acacia Leprosa or “Cinnamon Wattle” which in itself is a very common tree which puts on a spectacular show of golden blossoms in late winter all across the state. In 1995 some bushwalkers in eastern Melbourne stumbled upon a remarkable find. In amongst the hectares of Acacia Leprosa which were in flower that year, they stumbled upon a specimen that had bright red flowers instead of the standard bright yellow. This was the only time ever this has been documented, and at first the bushwalkers thought they had discovered a new species altogether. They took some cuttings back to Melbourne’s Royal Botanic Gardens, where they were able to propagate these cuttings. This plant is now in wide distribution, and I think you’ll agree it is quite spectacular when in bloom. It has since been named Acacia Leprosa “Scarlet Blaze”.

Being a relatively short-lived tree, maybe only 10 years or so, the original tree is now long dead. But the cuttings, of which I have one in my back yard, have spread far across the country with the help of mankind. The only way they were able to cultivate this tree was with cuttings, as seed propagation caused the blooms to return to the normal golden-yellow state.

This find is remarkable for several reasons. This is the only time this kind of mutation has been documented in this species, and the only time a wattle has been seen with a red colouration. The tree, whose DNA is identical to those around it except for the mutation which caused the red colouration. But most importantly, this mutation is a perfect example of how mutations can prove to be beneficial to a species. And through human intervention, we have a brilliant example of natural selection. An important thing to note here is that the “Scarlet Blaze”, unlike most plants which reproduce by the fertilization and germination of seeds, is actually a clone of the original plant, so it retains all the characteristics of the original plant. And in a way, all the commercially bought examples of this plant are actually the same plant, much like commercial apple trees or grafted roses. By human intervention, we have extended the lifespan of this particular tree to more than double what it would have been in the wild, and there’s no reason why it couldn’t continue indefinitely with human intervention.

In earlier articles I have written, I proposed the idea that nothing is unnatural, that everything that happens does so because that is the way the laws of physics and chemistry work. So the idea that just because humans have intervened to propagate this flowering wattle makes it no less of a natural selection than the evolution of a slightly superior eye on a flatworm over its predecessors. The benefit here is that we as a species find the red-flowers to be appealing, and that the novelty value of such a mutation is desirable.

In the same way, humans have taken random mutations of plants and animals and propagated them to perpetuate the trait in later generations of the species. Almost all plants and animals we use for our domestic purposes have been selectively bred to enhance their usefulness to us and our societies. Dogs, cats, cattle, roses, apples, tulips, marijuana, tea, wheat, bananas, you name it, we have altered it to suit us. And we have taken a random mutation in Acacia Leprosa, which is useful to us on a more cerebral level, and have captured it for our own use

Another thing to keep in mind is the fact that this mutation has only changed the colouration of the flowers. The rest of the tree is indistinguishable from any other Acacia Leprosa, so the mutation appears to be only an aesthetic one. So humans notice this mutation easily, but to a bee the mutation may seem minor or imperceptible. So this mutation may only be beneficial to the one single tree because of humans and out ability to see colour the way we do, our ability to clone and propagate cuttings of the living organisms, and our ability to distribute these around the country. Had it not been for human intervention, this specimen would have simply died when it reached the end of its lifespan.

In the same way that this plant has managed to  continue its lifespan through being mildly beneficial to another species, many plants and animals, through random mutations and slight changes over a long period of time, have increased their chances of survival by being beneficial to another species. Orchids are a great example of this, and there are many species of orchids which mimic their pollinators to lure them into believing that they are mating with one of their own kind, when in fact they are actually acting as carriers of pollen. This video from a David Attenborough documentary shows this in action.

So natural selection is not only talking about beneficial mutations to the organism itself, as in a kangaroo that can hop faster than others around it, or a bird which has a better knack for collecting coloured baubles to attract a mate. Natural selection also speaks of mutations to a species that benefits it by its effect on other species which interact with it as well. And remembering that most mutations are not as striking as the colour mutation of Acacia Leprosa, they can take millions of generations to occur.

To think that evolution has stopped at us, and with humans and human society as some sort of goal reached, is folly. Evolution is occurring around us all the time, and within us as a species. Evolution continues, and will continue forever, as long as there is a species alive which has an evolutionary past.

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5 Comments

  1. As a scientist and molecular geneticist with 20 years research experience, I would note that the idea that mutations are random is speculation in the absence of theory.

    I know how I change My genetic composition. I have the theory that explains it. And I do it quite deliberately, not randomly.

    Peace,

    Ik

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  2. Likewise, the coevolution of Euglossine bees and orchids is fantastic. The bees evolve to pollinate a single species of orchid, who rewards its helper by providing chemicals that help the bee’s longevity and making sure no other types of bees get the pollen by evolving a unique structure. Fascinating behavior.

    Or what about the fig wasps. Fig synconiums are clusters of flowers in a tough coating. There are three kinds of flowers in the synconium: male, female, and sterile (gall flowers). They mature at different rates. The females develop first, followed by the males, who cannot pollinate the females as a result. So, fig wasps, who lay eggs in the gall flowers, come into the picture. The fig wasp males develop first and impregnate the unhatched females. The females then hatch and climb over the recently developed male flowers. They then burst out of the synconium, and fly to another where they lay their eggs in the gall flowers, but not before climbing over female flowers and fertilizing them. Crazy. Evolution is absolutely crazy. I love it!

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  3. I have often thought that artificial selection is only meaningful to humans and thus an entirely human distinction. Sure without human intervention, it is doubtful that cows, orchids, and dogs would have been naturally selected to produce the outcomes we see today. But from a certain point of view that accepts human impact on the natural world as part of the natural world, artificial selection does seem kind of a strange distinction to make.

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  4. Marty,

    An interesting spin on natural selection. Darwin argued by analogy from breeding by farmers etc to explain natural selection. And you’re arguing that there is no non-natural selection, it’s all natural, we’re all part of one system. Fascinating.

    Can we take this line of thinking one step further?

    Global warming: doesn’t this line of thinking absolve humanity of any culpability in (the growing consensus that human activity is) causing climate change? It’s all natural, we’re all part of one system. How do you distinguish human decisions that are natural, explicable, excusable, from those that are monstrous? (in a rational way, not one that relies on my preferences)

    Thanks for the interesting post,
    Ken

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    • Glad you brought this up Ken. Just because I imply that human action is part of natural process doesn’t even come close to absolving humans of bad decision making. We are but one species in the world, and what we do is a byproduct of our own evolution. At least this is my take on it. We can’t escape what we are as a species, but by our ability to make changes to our environment and planet is something we can control. I see that we can recognise this and make educated changes to our environment rather than the haphazard changes we have made in the past.

      I was actually picked up on this by a biologist who took issue with my ultra-reductionist viewpoint, but he conceded that on a universal scale this is correct.

      I am a humanist, but sometimes the truth about humans is that we are very good at making short range decisions with far reaching consequences. We can learn to avoid this by learning from our errors from the past.

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