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The Physiology of Marriage
New studies showing how human physiology is designed for marriage, not multiple partners

This page is not an authoritative statement, but a collection of study sources about the physiology of marriage. The thesis is that both male and female bodies were specifically designed so that health is optimized by a monogamous relationship between husband and wife. Questions, comments, refutations or suggestions would be appreciated. Send to

Since virtually all higher education teaches that mankind evolved from single celled-life, and since many species of animals do not mate for life, then there would be no particular reason to believe that human physiology would favor marriage over multiple partners. And hence, biologists have rarely looked for it.

Economic concerns point researchers down a similar path. Monogamous marriage has resulted in the production of untold generations, nearly everyone believes it works, and there would be little economic benefits from proving it works. Whereas, promotion of sex for entertainment is a big business, and studies claiming to find ways to make it safer or better are likely to have financial backers.

Biologists and health practitioners certainly recognize the advantages of monogamy in reducing Sexually Transmissible Infections (STIs, formerly called STDs). Their answer, of course, is to reduce the risk of them through various prophylactic products and recommended procedures for sexual activity. The lack of effectiveness of these methods and STI epidemic have been well documented on other websites for years: 2014 2007 2006 2005 1993. This page will not focus on STDs, though they are very important, but on the other physiological effects of monogamous verses multi-partner sex.

Offsite Links on This Subject
What happens to Women with each Sex Partner?
11-minute video interview with Vicki Thorne.
Full 71-minute presentation is in three videos below. Biological information sources are documented in the link below them.
The Bio-Chemistry of Sex Part 1
with Vicky Thorn, 34 minute video
The Bio-Chemistry of Sex Part 2
with Vicky Thorn, 21 minute video
The Bio-Chemistry of Sex Part 3
with Vicky Thorn, 15 minute video
What They Didn't Teach You in Sex Ed
with Vicky Thorn, 90 minute video
Lecture summary: The Biochemistry of Sex, St. Therese Lecture, Thursday, February 19, 2009
Sources for above videos, 6 pages
Our Selves, Other Cells
Some of a baby's cells stay in its mother, her baby keeps some of hers.
Testosterone, Estradiol Levels Drop In New Dads During Partners' Pregnancies; Hormonal Changes Occur Earlier Than Once Thought

Traditional Beliefs, Apparently in Error


What New Science Appears To Be Discovering

The act of sexual intercourse has been considered a "one-time event". If people are properly protected, they will not get an STD and a pregnancy will not occur and that is the end of the matter. There are no long term effects. It is simply a mental decision for each of the two to decide whether they want to have sex together again, or move on to other partners.


Both men and women are forever changed by sexual intercourse. The woman retains genetic material from the man. Sex with multiple partners can harm the immune system of the woman. Both sexes imprint on the other and will associate sights, sounds and smells of previous partners with sex in the future.

Using birth control is like following the instructions for any other product. Once one has learned the procedure and is using it properly, it should offer reliable protection against pregnancy. This is especially true if one is using more than one type of birth control. If one or the other person fails to use birth control 5% of the time, then there is only a 5% greater risk of pregnancy.


Sexual intercourse is driven much more by emotions and hormones than thought and logic. Couples are much more likely to forget or fail to properly use birth control at the times that they can get pregnant. When emotions and hormones are at a high level, the human body is able to defeat certain kinds of birth control. On the other side, regular, prolonged use of birth control has negative health effects and can cause negative responses between couples.

Once a child is conceived, a mother has the choice to keep it and breast feed it, keep it and bottle feed it, have someone else feed it, put it up for adoption or abort it. This choice has no bearing on her future health or capacity to have more children.


Once a woman becomes pregnant, a set of chemical changes are begun in her body. If she is not able to deliver the baby and breast feed it, there are negative physiological consequences. Women who abort babies are plagued with devastating emotions from days after they do it to many years later.

A man's body does not change at all because his partner is pregnant. It doesn't matter if he lives with her or not.


A man living with a pregnant women will go through hormonal changes also, making him more suited to help take care of a baby. This allows him to enjoy the baby, not see the baby as a financial burden. Click references 1 2 3 4.

Once a woman has ended a pregnancy, that child is no longer a part of her. If she has a new partner and has children by him, there will be no lasting physiological effects of the previous children.


Women retain cells from their babies for decades, maybe their whole lives. Babies retain some cells from their mother, as well. We are just beginning to learn the interrelationships between all the children that a mother conceives.