Today's post is from Hanne Blank, author of Straight: The Surprisingly Short History of Heterosexuality. Blank is a writer, historian, and public speaker whose work has been featured everywhere from Out to Penthouse. An independent scholar, she is the author of Virgin: The Untouched History and seven other books that explore the intersections of sexuality, gender, the body, and culture. 

This post originally appeared at Huffington Post. 

When I began work on my book Straight: The Surprisingly Short History of Heterosexuality, I often got teased by friends who wondered whether, in working on the history of something so commonplace, I was going to come across anything that wasn't already common knowledge. Surely, they thought, it would all be very straightforward, very vanilla, very Leave It to Beaver, and if there were anything in there they didn't already know about, they'd be surprised.

As it turned out, this was far from true. The history of heterosexuality is actually a motherlode of remarkable and sometimes deeply strange stuff, from the broad-brush conceptual to the kinds of tidbits you add to your cocktail-party repertoire. Not only does the history of heterosexuality offer up surprises that make you rethink what "heterosexual" is and means, it also makes you realize how little we really know about this thing about which most of us assume we already know everything we need to. The following are 10 of my personal favorites.

1. May 6, 1868

The words "heterosexual" and "homosexual" were coined on this day in a letter written by Austro-Hungarian journalist Karl-Maria Kertbeny to the German legal eagle and proto-gay rights crusader Karl Ulrichs.

Technically speaking, before that fateful Wednesday, it was impossible for anyone in the world to be either a heterosexual or a homosexual, because the words didn't exist yet. [Image: First mention of the word "homosexual" and "heterosexual" (in a letter from the Austro-Hungarianwriter / from) Karl Maria Kertbeny in 1868 Photo: Hungarian National Library.]

Not Kirchberg and Feenstra. [Photo: NBC Universal]

2. Kirchberg vs Feenstra

Married American women didn't gain full legal control over their own financial assets until after this landmark U.S. Supreme Court case in 1981. In overturning "head and master" laws that gave husbands a legal upper hand over financial decision making within marriages, this decision finally made it illegal for a husband like Louisianan Joan Feenstra's, awaiting trial for sexually molesting his daughter, to decide to do something classy like mortgage the house for which his wife had paid in order to pay his legal bills. (And no, that date's not a typo: 1981.)

3. The "Science" of Mutual Heterosexual Orgasm

The ideal that men and women should have mutually orgasmic sex developed during the same time period as the idea of "heterosexuality" did, in the late 1800s and early 1900s. This novel notion helped establish the new notion of distinctively "heterosexual" desire and pleasure as scientific and medically proper.

By 1922, Dr. Walter Robie would write that married coitus had to be "mutually pleasurable and simultaneously climactic... if it is to be scientifically correct."

4. Science Has Never Defined "Heterosexual"

Never mind the question of whether there's such a thing as distinctively "gay genes" or "gay brains"; we don't even know if there's such a thing as straight ones. Physical and biomedical science have yet to define or even confirm the empirical existence of heterosexuality... no one's ever even tried.

This means that scientific research being conducted on the question of what makes people gay is being done without a properly characterized control to compare with. That's bad science. 

5. Survey Says... We Lie a Lot About Sex

If you think you're better off trusting the statistics in sex surveys than what your friends say about their sex lives for an idea of what "normal heterosexuality" looks like, think again.

Research done on the accuracy of self-reporting in sexuality surveys, including a 2009 study in the Journal of Sex Research, demonstrates that in sex research as in life, what people claim about their sex lives often doesn't match up to reality. A better bet is to consider sex research stats as a representation of what's possible, not what's typical. 

6. Freud, Father of Foreplay

Though men and women have engaged in various forms of non-intercourse sexual activity since time immemorial, the idea that there was a necessary opening act to sexual intercourse called "foreplay" is something we owe to Sigmund Freud and a handful of other psychologists and medical types around the turn of the 20th century.

7. When Going Down Meant Going... Down

Some late 19th-century authorities and physicians believed very sincerely that any woman who was interested in having a man perform oral sex on her was a sadist, and any man who complied was dangerously passive and submissive. Performing oral sex on women, they believed, was a "gateway drug" that led inevitably to ever more depraved acts of submission, and could possibly drag men all the way down to what they saw as the bottom of the heap, making them into the kind of men who provided oral sex to other men.

8. What's Love Got to Do With It

For most of Western history, it was considered shameful to feel or display too much romantic emotion toward a spouse. Treating one's wife "as one would a mistress" was excessive and unseemly; as the Lady's Magazine lectured its English readership in 1774, "the intent of matrimony is not for man and his wife to be always taken up with each other, but jointly to discharge the duties of civil society, to govern their families with prudence, and educate their children with discretion." Love, shmove, marriage was a job -- not an adventure. 

9. Great-Great Grandma Used Birth Control

A passionate commitment to contraception was a part of many male-female relationships long before the Pill or even commercial condoms came on the scene. Statistical research shows that men and women began to limit their fertility during the 19th century, with birthrates among American white women declining from an average of seven babies per woman in 1800 to only about three and a half in 1900... not the sort of drop that happens spontaneously.

What were great-great grandma and grandpa using? Probably withdrawal.

10. Heterosexual? Thank a Gay Rights Activist

"Heterosexual" is not, and never was, a scientific term. Nor is "homosexual." Both were coined in the context of what we'd now call gay rights activism, during a campaign of pamphleteering and letter-writing in opposition to a mid-19th-century German sodomy law.

The idea behind the words "heterosexual" and "homosexual" was to demonstrate through language that these were merely two ways in which human beings could be sexual, distinct and equal, with the implication that sodomy laws should apply equally to everyone... or else to no one at all. 

Survey photo from Bigstock.

Watch Hanne Blank talk about her new book, Straight: The Surprisingly Short History of Heterosexuality