Originally Posted by
KissingCommies
I suppose I could ask, why is your skin cell not considered an organism, whereas an amoeba is? They're both cells. But a skin cell doesn't have independent reproduction capabilities, and thus does not evolve for the sake of itself, and thus does not serve itself. It is a cell that, over time, has been reduced to simply being created and used, not for itself, not for for another organism, but to a mass of other cells that are all similarly simple tools of the whole. At one point evolutionary history, the ancestors of your cells were indeed independent organisms. They probably started out as a moss, or some other mat of cells tightly bundled together, becoming more and more interdependent until they lost individuality and even an independent genetic code - and then they were one organism, instead of many. If an amoeba has a trait that doesn't contribute to it's own survival, that trait will die out. In contrast, a trait that leads to the death of an individual skin cell may very well survive if it leads to greater survivability of the whole. You see similar patterns in social insects, where reproduction is centralized at the colony level, since everything but the queen is sterile (the queen essentially being the ovaries of the organism).
A suborganism, such as a skin cell, an ant, or a liver, only really wants to survive because doing so furthers the needs of the organism. The organism itself only really wants to survive because doing so serves the purpose of propagating the genes (or, at least, this is the tendency; an organism may very well have no desire to survive, however, in the long run there will tend to be less of such creatures). A bee sustains itself and survives because the hive needs workers for honey, but it will gladly kill itself stinging an intruder in order to defend the hive. And a mother will provide sustenance for the fetus at the cost of her own livelihood, and will even protect a child at the cost of her own life. Why? The genes make a rational calculation, and they have more to gain from the creation of a new organism with 50% of their genetic content than they do from the remaining childbearing years and life expectancy of an organism with 100%.
Also, you are completely wrong on one point. The fetus does has all of the capabilities necessary to carry on the processes of life. The fact that it has strict environmental requirements - the womb of a mother - at best would make it parasitic (which would really be a rather silly way to describe something necessary to sustain the species, but whatever). If there were a creature that somehow evolved to convince another creature to utterly sustain it in some way, without even having to contribute anything, utterly bypassing any defense mechanisms, that would simply be a successful evolutionary strategy. It wouldn't mean it was no longer an organism - it would mean that it's a smart organism. Let's imagine, for the hell of it, that the parasitic species somehow convinced host species to develop a special organ inside it's body for the parasite to be comfortable in, where the host provided the parasite with nutrition, oxygen, and waste disposal. Let's also imagine the the host species started trading the sperm and eggs of the parasite between each other, so that the parasite would literally have all of its needs taken care of. Eventually, I suppose, the parasite would lost the ability to leave the host organism, since there would be no need. It would simply sit inside of the host organism its entire life, having all its needs taken care of - certainly an even more extreme example than the fetus, which at least leaves the host at some point. Would the parasite then somehow be part of the host? I'd honestly say it's more the other way around - the host would be more like an organ of the parasite. Of course, this is an evolutionary absurdity, but that's not really the point.
Of course, the fetus only gets a sweet deal because the genes want the fetus. Since the organism ultimately serves the genes, even to its own detriment, it is designed to pop out the fetus. The subunits of the organism, such as the womb, the digestive system, the ventilation system, and the waste disposal system, similarly fall in line, reworking themselves so that they support it's life functions as well as the mothers. You can't compare to an internal organ like a liver. Sure, they both require an environment that their host provides. But there is reciprocity in your relationship with your liver - the liver pulls its own weight, and gets the sustenance it needs in order to sustain the organism. In contrast, a fetus doesn't do anything to sustain the host organism, it simply takes. I think the confusion here is caused by the fact that you think that, because the organism takes care of the fetus, the fetus is somehow subservient to the organism. It is true that we take care of things we own. However, we also take care of things that own us, and to a much greater degree. And that would be a better description of the parent-child relationship in most of nature.
With humans, of course it's somewhat different, because we're not totally driven by instinct, so we're more inclined to think of our own happiness that to obey instinctual commands our genes give us. We also have social obligations (like avoiding overpopulation) that don't concern most species. However, the relationship of a fetus to a mother could still not be considered like that of a organism to one of its suborganisms.
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