You also said "size of the human brain has been shrinking". It's one thing to say that small-brained people walk among us and live out their lives: all kinds of people do. Do I need some evolutionary "explanation" for that? No.
I said nothing about variable sizes of brains of existing people. Since I said nothing about that, why do you bring that up? (You give a perfect example of a straw man argument: bring up something that was not said, and then argue against that instead of what the other person actually said.)
Once again, what I said was that the size of the human brain has been shrinking. Over the last 10,000 years, the human brain has shrunk about 10% in size.
Come now, if women didn't prefer small-headed men then how do you imagine human noggins are shrinking? So it must be that they do prefer them. But despite the assurances of science, I find it hard to believe that there is a general preference for small-headed men among women, even if it is subconscious. As far as I know, Zip the Pinhead wasn't successful with the ladies. But no doubt an evolutionist could argue that Zip was an isolated case and provide numerous examples of pinheads who are reproductively successful and have pinheaded children and so on, etc., etc.
Selective pressures consist of many more factors than merely which mates the opposite sex finds more attractive. Some traits may be extremely attractive to a mate, but carry with them a distinct survival disadvantage. Go back and reread my previous post, #59--my example there contained both positive and negative effects.
As a dramatic example of the difference between mate preference and survival advantage, consider this: many male birds put on elaborate displays of plumage to attract females. They have very bright and large feathers, and they puff themselves up to look very pretty for the females. Unfortunately, the more puffy and colorful they look, the more they capture the attention of predators. So the males who are the most attractive to females rarely get a chance to reproduce and the males that reproduce are those that are balanced between being just attractive enough for the ladies, but not so much that they draw the predators.
BTW, quit bringing up things I never said.
Indeed, as we all know, smart people are the first to starve when times get tough.
Under normal circumstances, the brain uses ~20% of the body's total energy intake. Under periods of starvation, the brain's energy needs do not decrease. In a situation of a limited food supply, people with higher energy needs--those with the largest brains and those with the most rapid metabolisms--have a distinct survival disadvantage.
You started out by saying that small brains are "not a disadvantage" and this assertion slowly but surely evolved into small brains are an advantage. Such is the nature of these Darwinistic explanations, it makes no difference if a trait is advantageous, disadvantageous, or neither: the fantastical natural selection narratives people fantasize about simply must be true no matter what the case.
I seriously doubt you've ever taken vector physics, but the progress of evolution over time is very analogous to the movement of an object subjected to many forces, whose trajectory and speed is determined by the vector total of the applied forces. Many selective pressures act on a species, and the characteristics of that species reflect the vector total effect of all the selective pressures. Also, as illustrated in the bird example above, traits are rarely purely positive or purely negative in their effect on survival. If higher intelligence, roughly correlated with larger brain size, confers a distinct survival advantage, then larger brain size also confers a distinct survival disadvantage for the large-headed baby trying to exit its mother's birth canal.
BTW, your use of the word "Darwinistic" rather than the correct term "evolutionary" tells me that you are making the mistake of trying to dismiss science as just another religion, equivalent to Christianity, Creationism, Buddhism, Islam, etc. I know that the creationist websites constantly try to denigrate science in this manner. The fact that they compare science to religion in order to "bring down" science tells me that they have a very low opinion of religion, most specifically Christianity. My advice is to stay away from those websites; they have *nothing* of value to offer. They lie about science *and* Christianity.
You said: "a smaller brain is not a disadvantage for survival". We can see that all kinds of people live around us. It isn't an Darwinian revelation.
Over the last 10,000 years, the human brain has shrunk about 10% in size.
I see. Those cave men needed big brains for spear-chucking, while small brains are the order of the day in our modern world full of modern medicine, high literacy, mathematics, astonishing engineering feats, etc etc.
Previously you said that a larger brain "little as a century or so ago was a death sentence for both mother and child" and now you say that 10,000 years ago people had larger brains. Did they also have advanced medicine? Maybe they worked on elliptic curves and classifying finite simple groups when they weren't using their big brains to chuck spears.
Or rather than postulate more tiresome Darwinian stories in an attempt to reconcile this contradiction, we can instead conclude that Darwinism is false, and your stories are not true.
the brain uses ~20% of the body's total energy intake. Under periods of starvation... a distinct survival disadvantage.
You're talking about a 10 percent difference in brain size, which amounts to 2% of energy intake. And this 2% is spread out over, as you say, 10,000 years, which at any time amounts to an imperceptible fraction of a percent. And you say it's a "distinct survival disadvantage". I don't believe your story.
I seriously doubt you've ever taken vector physics,
You may be right, I've long been hampered with the evolutionary disadvantage of not having a small brain. If only it were smaller, whole vistas of modern intellectual fields would become accessible to me: mathematics, medicine, computer programming... Maybe I would even do my own taxes too and not have to hire a small-brained accountant to help me.
the progress of evolution over time is very analogous to the movement of an object subjected to many forces, whose trajectory and speed is determined by the vector total of the applied forces. Many selective pressures act on a species, and the characteristics of that species reflect the vector total effect of all the selective pressures.
That's a really beautiful story. I can sit down and imagine all those pointy vectors. It reminds me of another really beautiful picture: Ptolemy's solar system, with all those lovely epicycles and the equant point and all that. Except for this very important difference: there were, at least back then, some good reasons to believe what Ptolemy was saying.
they compare science to religion in order to "bring down" science tells me that they have a very low opinion of religion,
How about comparing Darwinism to Marxism or some other psychotic 19th century ideology? Would you have less of a problem with that?