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The amoeba is one cell of a guy – especially when a bunch of them get together

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File:Slime mold stemonitis fusca.jpg
Slime mold stemonitis fusca/Farnishk
At the New York Times, Carl Zimmer asks, Can Answers to Evolution Be Found in Slime? (October 3, 2011). The short answer is yes, certainly, but if you really must insist that all the answers be Darwinian, well then no, not really. Of course not. Here’s Zimmer on how slime molds (colonies of amoebas) can act like a multi-celled animal:

Today, biologists no longer think of Dictyostelium as an embryo: It is more like a society of amoebas that come together for a common cause, for which some will sacrifice themselves.

The organisms respond to starvation by rushing together by the thousands into a single blob. The blob stretches out into a slug-shaped mass about one millimeter long (one twenty-fifth of an inch), which then crawls like a worm toward light.

You could actually see it. It’s somewhat like this: –

Once it reaches the surface of the soil, the slug undergoes another transformation: Some of the cells turn into a stiff stalk, while the others crawl to the top and form a sticky ball of spores. They stick to the foot of an animal and travel to a hospitable place.

Inside the slug, about 1 percent of the amoebas turn into police. They crawl through the slug in search of infectious bacteria. When the amoebas find a pathogen, they devour it. These sentinels then drop away from the slug, taking the pathogen with it. They then die of the infection, while the slug remains healthy.

More amazing stuff. What it all demonstrates is that life forms need not become official multicellular animals in order to achieve some of the benefits – provided, of course, that they aim no higher than, say, the slug. (It could get testy if they needed a Parliament … )

2 Replies to “The amoeba is one cell of a guy – especially when a bunch of them get together

  1. 1
    englishmaninistanbul says:

    I don’t know about anyone else but I find this kind of superorganism even more incredible than ants, because the inherent “altruism” is so much harder to explain.

    In an ant colony the members are not independently functioning and reproducing animals. They are programmed at birth for a specific role. So any “altruism” on their part is not really altruism because they are drones, effectively extensions of the queen.

    However in slime moulds you have a society of truly independent, functionally identical individuals. How on earth could they have developed these behaviours in a step-wise fashion?

    If slime molds arrived on land close to a billion years ago, they may well have colonized continents that were home only to films of bacteria.

    So we’re saying that first there was bacteria, and then some bacteria evolved into slime moulds, and then they conquered the world. Right. How does a lone-wolf bacteria, that basically just eats, fends for itself, and reproduces, produce offspring that knows how to be a responsible member of a society, with all the mechanisms necessary to know where it is in the mould, what it should be doing, what it passes to who, and if when and how it should end its own life for the greater good?

    Added to which, what use is a bacteria that knows how to function in even the most basic society when it’s the first of its kind, ie. said society does not yet exist?

    Here’s a question: Could an inherited behaviour set be viewed as irreducibly complex?

  2. 2
    ScottAndrews says:

    Behaviors are at least as interesting as physical variations, and almost always work hand-in-hand with them. No one ever wants to explain how they evolve.

    Take the bird that pretends to be wounded to lure a predator away from its nest. What genetic or regulatory change was the first step toward that behavior, and why was it beneficial – so beneficial that it resulted in differential reproduction?

    Or bees that discover a food source and somehow have the foresight to know that the knowledge should be shared. At what point does a bee return to the hive and begin to make movements that correspond to the distance and direction it traveled? How many steps does it take for such behavior to evolve? What is the first step? Why does that first step result in differential reproduction? And what is the next step?

    I’m reasonable and I know that accurate historical detail would be impossible to obtain. But I’d settle for some really good imagination that incorporates the genetic or regulatory variation, the specific change in behavior, and how it resulted in differential reproduction.

    In these two cases I’d be curious to hear a narrative, any narrative, even if it omits the variation, provided that the behavioral change can be reasonably attributed to a single one.

    The truth is that darwinists literally cannot imagine how their own theory might work.

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