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Humans and squid evolved same eyes using same genes

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…

I see how you see. actor212, CC BY-NC-ND

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.

Eyes are the prize

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.

The Pax6 gene now directs the formation of an amazing diversity of eye types. Beyond the simple eye, it is responsible for insects' compound eye, which uses a group of many light-sensing parts to construct a full image. It is also responsible for the type of eye we share with our vertebrate kin: camera eye, an enclosed structure with its iris and lens, liquid interior, and image-sensing retina.

In order to create such an elaborate structure, the activities Pax6 controlled became more complex. To accommodate this, evolution increased the number of instructions that arose from a single Pax6 gene.

Complex beauty. pacificklaus, CC BY-NC

Making the cut

Like all genes, the Pax6 gene is an instruction written in DNA code. In order for the code to work, the DNA needs to be read and then copied into a different kind of code. The other code is called RNA.

RNA code is interesting in that it can be edited. One kind of editing, called splicing, removes a piece from the middle of the code, and stitches the two ends together. The marvel of splicing is that it can be used to produce two different kinds of instructions from the same piece of RNA code. RNA made from the Pax6 can be spliced in just such a manner. As a consequence, two different kinds of instructions can be generated from the same Pax6 RNA.

In the new study, Atsushi Ogura at the Nagahama Institute of Bio-Science and Technology and colleagues found that Pax6 RNA splicing has been used to create a camera eye in a surprising lineage. It occurs in the lineage that includes squid, cuttlefish, and octopus – the cephalopods.

Cephalopods have a camera eye with the same features as the vertebrate camera eye. Importantly, the cephalopod camera eye arose completely independently from ours. The last common ancestor of cephalopods and vertebrates existed more than 500m years ago.

Pax6 RNA splicing in cepahlopods is a wonderful demonstration of how evolution fashions equivalent solutions via entirely different routes. Using analogous structures, evolution can provide remarkable innovations.

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50 Comments sorted by

  1. Theo Tsourdalakis

    logged in via Facebook

    This article is full of ASSUMPTIONS and INTERPRETATIONS masqaurading as scientific facts.
    The first line is an example of this. "Eyes and wings are amongst the most stunning innovations evolution has created."

    NO-ONE has observed eyes or wings forming - the authors inveference that it definitely occured and is a "stunning innovation of evolution" is fantasy and poor science.

    This article PRESUMES molecules to man evolution (=Darwinian/Macro evolution)is a scientific fact - but is it?
    Consider…

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    1. Theo Tsourdalakis

      logged in via Facebook

      In reply to Delma Clifton

      woohooo - a new version of reason denial on The Conversation.

      If you can provide a reasoned rebuttal - lets hear it; but your casual scoffing is silly.

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    2. David Maddern

      logged in via Facebook

      In reply to Theo Tsourdalakis

      Let's put one of those to bed.
      what came first the chicken or the egg? You ask
      The egg, clearly
      Back when a distant flying dinosoar ancestor of the chicken laid an egg to carry on the line the egg existed, the chicken didn't.
      The egg came first. Amen.

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    3. Paul Miller

      logged in via LinkedIn

      In reply to David Maddern

      The conundrum is really about which came first, the creature that lays the egg or the egg from which the egg laying creature hatches.

      Unless we mangle our definition as to what constitutes an 'egg' the answer would surely be that the creature came first, having been created from something that was not an egg.

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    4. Paul Miller

      logged in via LinkedIn

      In reply to Theo Tsourdalakis

      1) Where did the information come from to build the DNA molecule?

      DNA could have evolved gradually from a simpler replicator; RNA is a likely candidate, since it can catalyze its own duplication. The RNA itself could have had simpler precursors, such as peptide nucleic acids. A deoxyribozyme can both catalyze its own replication and function to cleave RNA.

      2) How did genders "evolve" from asexual organisms?

      The variety of life cycles is very great. It is not simply a matter of being sexual…

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    5. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Paul Miller

      Personally I think just from the "logistics" of reproduction, hermaphrodite creatures that have both "male" and "female" parts capable of fertilising themselves must have evolved first, and then broken into creatures that fertilised each other.

      See Dr John Long's book "Hung Like An Argentine Duck" - "A journey back in time to the origins of sexual intimacy". Great explanation of the fossil record going back more than 350 million years proving that sexual reproduction started a very long time ago.

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    6. David Maddern

      logged in via Facebook

      In reply to Paul Miller

      The fact is the egg is a more general object than the chicken (crocodiles, echinus, all birds) it follows in the string of egg laying that occurred before the chicken evolved, one of the eggs was laid by chicken progenitors, so the egg came first.
      I think it is only a conundrum if you write an god and a creation event into it, although there's nothing for a god to do. The chicken only came from the Indian Jungle Fowl because at least some of every generation the egg laying and hatching worked. We wouldn't know it if it didn't.

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    7. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to David Maddern

      It depends what you mean by "egg". An embryo can exist / develop / evolve within the mother's body. This always comes first. The evolution of a shell / protective case is only necessary when the embryo is ejected by the mother (for some reason) and there are different variations (hard bird shell, leathery reptile shellm soft amphibian shell and so on).

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    8. Lucas Lock

      logged in via Facebook

      In reply to Theo Tsourdalakis

      Ill be honest I certainly did not read your entire post ;)... but why?

      its simple for me, for many readers too. The reason I did not fully finish your post is because even though you touched my heart with all of this evidence shit... you seriously forgot one simple factor.

      science is more than okay and even very happy with changing opinions. the best part about science is its ability to change its mind and even more so its lack of ability to stay on course with opinions and I fully agree…

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    9. Paul Prociv

      ex medical academic; botanical engineer at University of Queensland

      In reply to Theo Tsourdalakis

      Theo, your post, and that little video to which you refer, are so riddled with errors and ignorance that it's impossible for me to know where to begin -- and I don't want to waste my time by addressing all your ignorant quibbles. But one thing I must address is an item right at the beginning of the video, also featured in most (all?) of the responses to your post, which highlight a widespread and fundamental ignorance of the evolution of sex in vertebrates. Even Darwin got it wrong, but he could…

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    10. Lucas Lock

      logged in via Facebook

      In reply to Lucas Lock

      I will however add to my original post that the original commentator is looking at this like one thing has to come before the other, nature does not work in those conditions when you consider that the penis and vagina evolved together and even followed obscure things like weather.

      its a duet my friend... nature tries to select qualities that hold desire, sometimes it is wrong, sometimes it is not. what works is what makes babies... so we get babies.

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    11. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Paul Prociv

      Paul, I am repeating myself, but get John Long's book "Hung Like An Argentine Duck" where he discusses discovering fossilised fish dating back 350 million years that contain fossilised embryos in situ - that is, full sexual reproduction back then.
      See http://en.wikipedia.org/wiki/John_A._Long

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    12. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Theo Tsourdalakis

      "You can't create information with misspellings, not even if you use natural selection.” What about the dyselexic Dog that thought it had unusual powers?

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    13. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Theo Tsourdalakis

      Sorry Theo, I notice you have just joined in. "Casual scoffing" is our way of saying "Welcome".

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    14. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Lucas Lock

      Some people have navels that go in, some have navels that poke out. Next time you are having sex, try "docking" your navels.

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    15. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Theo Tsourdalakis

      "- Consider some of the challenges, have a look at this video http://youtu.be/Ab1VWQEnnwM";
      I just wasted 11 minutes of my life on this tripe! However, I like the way he tells children less than 13 (unlucky number? puberty? impressionability?) to go away.

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    16. Paul Prociv

      ex medical academic; botanical engineer at University of Queensland

      In reply to Robert Molyneux

      Robert, I was familiar with that story, but miss its relevance to my comment. I'm saying that sexual reproduction was already established in the ancestral lineage of all metazoa, even before the first chordates appeared, so it would have been there already in the pre-Cambrian explosion. It's no surprise at all that some early fish were viviparous.

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    17. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Paul Prociv

      Paul, thanks for your information.
      I think Long's discoveries showed that the gadgets, processes and mechanisms for viviparous reproduction were developed many moons ago.
      As to the idea that "sexual reproduction was already established in the ancestral lineage of all metazoa", I bow to your superior knowledge. I find the whole thing intriguing, including the idea that hermaphroditic and parthenogenic reproduction came AFTER sexual reproduction. I read somewhere (Long?) that (some) sharks are capable of parthenogenic reproduction.
      Any pointers to this topic gratefully received.

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    18. Theo Tsourdalakis

      logged in via Facebook

      In reply to Paul Miller

      Paul; thanks for your galant attempt at answers to these fundumental questions but frankly I find your answers very unsatisfying.

      I think they have very little scientific credibility; and would satisfy only those who are believers in Evolution and are not inclined to scrutinize the evidence.

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    19. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Theo Tsourdalakis

      Theo, I think the real challenge for Creationists / Designers / Evolutionsist is parasitism.
      See http://en.wikipedia.org/wiki/Parasitoid_wasp
      I will look for links for parasites that have sequential multiple hosts - eg Water - Pigs - Humans.
      The challenge is on the one hand, how did these creatures and their habits evolve, and on the other hand, if God designed them, she is an evil bitch and is probably related to parasitic wasps.
      See also the various creatures that parasitise us, such as worms that get into our eyes and blind us (see River Blindness).

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    20. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Theo Tsourdalakis

      "Which "evolved" first, the vagina or the penis?"
      1. All sexual creatures have passage(s) from the interior to the exterior of their bodies. The passages are needed for excretion and are handy for sexual reproduction.
      2. They may simply pump their gametes into surrounding water through water (fish) or they may oppose their orifices (birds) or they may use ovipositors (wasp egg positioners) or they may have a penis like a spear that is rammed into the female's body (an Israeli spider).
      3. The cloaca…

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    21. Paul Miller

      logged in via LinkedIn

      In reply to Theo Tsourdalakis

      Thank you Theo, but, to be honest, I don't actually care what you believe or find unsatisfying.

      Your anti-evolution stance and the questions you raise are fairly typical of a lazy thinker who would much rather seek out pseudo-scientific babble to buttress their fragile ideology than actually seek out evidence that would reveal how we developed on this planet.

      From a scientific standpoint, evolution through natural selection ticks pretty much all the boxes when it comes to explaining the development…

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    22. Yoron Hamber

      Thinking

      In reply to Paul Miller

      I would say cells of some sort came first, then came trial and error, with some system to catalogue them. Added with some principle leading from simplicity to complexity I would guess.

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    23. Theo Tsourdalakis

      logged in via Facebook

      In reply to Yoron Hamber

      I appreciate your honesty that what you are putting forward is a guess. What I find disturbing is that other authors make similar guesses in textbooks but represent them as scientific facts - this is deceptive and should be abhored.

      I have a problem with the core evolution assertion that from simplicity and chaos emerged complexity and order by the application of natural forces plus "millions of years". This goes against our observations and common sense.

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    24. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Theo Tsourdalakis

      Theo,
      We are talking about more than 350,000,000 years:
      17,500,000 of our generations (20 years)
      35,000,000 of a wild animal generation (say 10 years)
      350,000,000 of a smaller creature (say 1 year)
      3,500,000,000 of a primitive creature (say 1 month or so)
      So, you can look around at the variety of cattle, sheep, goats, cats, and dogs, and the variety of human beings around the world that have developed over the last 150,000 years or so, and claim that evolution "goes against our observations and common sense".

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    25. Theo Tsourdalakis

      logged in via Facebook

      In reply to Robert Molyneux

      Robert,
      with all due respect, the numbers you put forward are big numbers - but what do they proove or indicate?

      We observe things decaying, going from order to disorder unless an intelligent being gets involved. Molecules to man evolution believes the opposite. On what basis should we believe this to be true?

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    26. Paul Prociv

      ex medical academic; botanical engineer at University of Queensland

      In reply to Robert Molyneux

      Robert, I'm afraid that what I've written is purely my own ideas, based on decades of working with protozoan and metazoan parasites, amongst other things. It has always intrigued, and disappointed, me that zoologists generally (without exception, in my limited experience) assume that sex appeared de novo in the "higher animals", often thus betraying their ignorance (as I said, Darwin can be forgiven, but not modern scientists) of what the protozoa have been doing for billions of years (possibly…

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    27. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Theo Tsourdalakis

      Theo,
      Virtually all the creatures in the world are exposed to sunlight and certain chemicals that cause genetic changes. There are (known) probabilities of these occurring. Some help the organism survive, some don't.
      Organisms and parasites that kill use (thanks to the Great Designer) have very short lifetimes, and very quickly evolve - hence the new variations on diseases that are gradually defeating the drugs we use to save outselves.
      The more time passes, the more these sorts of evolutionary…

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    28. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Paul Prociv

      Paul, I think all this boils down to a simple question. Assume a flash of lighting. Given a blob of chemical compounds of DNA / RNA floating in a pond, and given the blob has a randomly created thin arm-like extension / flagella, what caused the flagella to start thrashing around and rowing the blob to somewhere useful - another blob, a patch of sunlight...
      As to molluscs and clams, I want to know why the Designer - Wasp spent so much time blowing Her nose into those neat little shell things.

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    29. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Theo Tsourdalakis

      Theo, it is a pleasure to speak to someone who accepts that living creatures have been around for about 500 million years.

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    30. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Paul Prociv

      Hi Paul,
      I would think that reproduction by parthenogensis (only one involved, no sex) hermaphrodites (one involved, potentially sex with oneself, potentially changing sex depending on circumstances)) and dioecious (our style, separate sexes) was the pathway followed.
      But you said that both parthenogenesis and hermaphroditism evolved AFTER dioecious. Any pointers / proof?
      Anyone know how to get my spell checker working?

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    31. David Maddern

      logged in via Facebook

      In reply to Robert Molyneux

      It doesn't depend on how the egg is defined. I can take the meaning to be calcareous shelled like a chickens egg or the female progenitor of the zygote, it came before the chicken, and I can define that chicken as a commercial 8 week old killer or the dinosoar with primordial feathers on its tail and wing tips, and the egg in time terms came before them.
      Paul Millar's conundrum is time independent and purely conceptual.
      I still maintain the egg wins it.

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    32. David Maddern

      logged in via Facebook

      In reply to Theo Tsourdalakis

      Look at in the business sense.
      A business with 10 employees and a business of five employees in a neighbouring town, both produce the same product for years. Transportation developments bring them into competition. Which one is better able to survive that?
      But the 10 employee firm gets a patented product line (advantageous mutation) and supplies the whole area and prospers.

      This is how natural selection works and in a Biological world we have a diversity in our society such that some people have lower oxygen saturation in their blood, by consequence of having a sickle cell gene or the Thallasaemia gene. If for instance a malarial parasite gains the ability to infect all mosquitos, these people will have an advantage.
      Or the walking dead scenario those normals that can get to an island, by operating a boat, a function the walkers can't perform, that Island big enough to defend and grow stuff, might be the ones that carry normal functioning into the future.

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    33. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Robert Molyneux

      BTW: The physics is that disorder is increasing - see Entropy. However, that is the average. There can be parts of the universe where entropy is decreasing (more order) surrounded by parts where entropy is increasing (less order). Absorption of energy (sunlight) allows an organism to "organise" itself for less entropy. And in due course we all decompose.

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  2. Paul Rogers

    Manager

    And of course, as our ancestors knew, that's the derivation of the word "squint" . . .

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  3. David Maddern

    logged in via Facebook

    You haven't explained how the squid got a better eye than us, although attacking a potato doesn't seem like good use of it. It has it's optic nerves running out the back of the eye, we have the nerves running across the front of the light gathering cells. We have a rather large brain to fill in the visual field we think we see, whereas the squid has four brains, doesn't he? I suspect his vision is not processed extensively like in us.

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    1. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to David Maddern

      David, you need to blame the Grand Designer for these sorts of strangenesses.

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    2. David Maddern

      logged in via Facebook

      In reply to Robert Molyneux

      I don't he's blameless, a shadow, or mirror, it just indicates divergent evolution, where both systems work for the beasts.

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  4. Mike Nelson

    Geoscience Manager

    The author says "evolution fashions equivalent solutions via entirely different routes." Evolution does not "fashion" anything. It has no design objective. The professor is letting his ID bias show. Evolution is purposeless. It has no objective! It does not innovate anything. It is purposeless and unguided. It does not "achieve" anything. Those are design termes. There is no design in evolution. Why do the academics have such a hard time with this concept?

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    1. Malcolm Campbell

      Professor & Vice-Principal Research at University of Toronto

      In reply to Mike Nelson

      The use of the word "fashion" implies no objective. It can be used synonymously for "make", which is the intent in the piece. In this regard, evolution fashions new innovations through the blind processes of random mutation and natural selection. It does not imply intelligent design at all. No other meaning should be read into the use of the word "fashion" in the piece. Plenty of other authors with no ID bias have used the word in an equivalent manner, including Dennett, Dawkins, and Wilson. Rest assured that the author of this particular piece similarly has no difficult with the concept of evolution, and certainly no ID bias.

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    2. David Maddern

      logged in via Facebook

      In reply to Mike Nelson

      Of course there is a design of something (a noun ) and to design. ( a verb)

      The pile where the World Trade Centre fell has a feature called a design in three dimensional space.
      Was it designed by Osama?
      Was it designed by war?
      No one was interested in that design.

      I design a compost heap but don't effect it, microbes do.
      You could say the microbes designed it, but no one is suggesting there was a designer, it was entropy, because plants take in CO 2 from the air and build structure, using the energy of the sun and that is the key self-organising organisms. That is the key to your entropy or designer statement. That is nature, that is social structures, that is built up techniques, materials, and made objects

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  5. Don Johnson

    Thinker

    Actually I've just recently solved the age-old question of the chicken and the egg.

    Well ... actually what I have solved is the question, and not the answer. You see the question is the wrong question "which came first, the chicken or the egg?"

    The proper question is "what came first, the male-female chicken pair or the egg?"
    The answer then is obvious - the first male and female chicken pair came before the first egg produced by that pair of chickens.

    Easy ... next question please.

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    1. Robert Molyneux

      Citizen at Drehmex Sales and Services

      In reply to Don Johnson

      Q. Why did the chicken cross the road?
      A. To increase its genetic variability.

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