That said, we do need to distinguish between fields. Phil argues that "Adjusted for IQ, quantitative skills, and working hours, jobs in science are the lowest paid in the United States." Would you make the same statement for jobs in literature? Are Lit professors as capable of pursuing these highly paid alternative career paths as the Math/Hard Sci/Engineering Ph.D's? It's a highly contentious question, I know.
I'd say that most lit Ph.D's probably don't have strong quant skills, nor do they have much of a science background. So they clearly are not choosing lit over a career in high finance or medicine. However, law is probably an option, so the women who pursue a lit Ph.D may be exhibiting at least some of the "irrationality" that the men are.
I guess it comes down to how you feel about the Science Ph.D vs Medicine, Finance or Law relative to the Humanities Ph.D vs Law only. If the situations are analagous (which is open to debate), I'd say you've uncovered a major flaw in Greenspun's "men are more irrational" argument.
I think Greenspun is off the mark on his reasons why people choose science, literature, or any relatively low-paying field. They get compensation in other ways, like being able to use their mind in creative ways. I consciously choose not to continue in Medicine because it's boring to me compared to building things. I've traded money and stability for more chaos and the ability to work more on my terms. If you talk to docs, you'll get another set of complaints -- malpractice insurance, hours (for some), paperwork.
Greenspun's points are well worth thinking about (as a grad student, I ponder them frequently), but the rant is a complete non sequitur. It offers nothing to explain the gender difference.
But he certainly doesn't show it. If that were the difference, women would avoid academic humanities and biology jobs, which they don't. And they wouldn't avoid programming and engineering jobs, but they do.
English Literature PhD programs are usually quite a bit smaller than those in just about any scientific field, and 100% of five people is still only five people.
Put another way: the "scientific careers suck and men are irrational" argument is perfectly consistent with a universe where out of every 100 women, 80 go to professional school (business/medicine/law), 15 go into science PhD programs, and 5 go into humanities PhD programs -- even if those 5 women represent nearly all of the humanities' enrollment. It just means that the few "irrational" women are disproportionately attracted to the humanities.