Intercourse Technique and the Determination of Sex: A Historical Overview

Abstract

The belief that sexual technique—particularly penetration depth—may determine the sex of offspring has a long and varied history. From classical Greek natural philosophy to medieval Islamic medicine, from Daoist sexual manuals to twentieth-century reproductive theory, this idea has persisted across cultures. This article traces its intellectual lineage, culminating in the “Shettles Method” of the 1960s, which popularised the notion that penetration depth could favour either Y- or X-bearing sperm, thereby influencing the likelihood of conceiving a boy or a girl.

Introduction

Sex determination has historically fascinated human societies, inspiring theories that range from philosophical speculation to biological hypotheses. Among the most persistent is the claim that the manner of intercourse—particularly the depth of penetration—can sway the outcome. Although modern reproductive science rejects such claims as empirically unfounded, their historical trajectory reveals much about human attempts to control one of life’s most fundamental outcomes.

Classical Foundations

• Greek medical and philosophical traditions provided some of the earliest systematic reflections on sex determination.

• Aristotle (384–322 BCE), in Generation of Animals, posited that offspring sex was determined by the relative strength and heat of the male generative principle: “the male is generated when the principle is hot and strong; the female when it is weaker or cooler” (Generation of Animals, IV.767b).

• Hippocrates (c. 460–370 BCE), in On the Nature of the Child, advanced a spatial model, claiming that semen deposited on the right side of the uterus produced male children, while semen deposited on the left side yielded female children (On the Nature of the Child, §13–14).

• Galen (129–c. 216 CE) extended the humoral framework, asserting that strong, hot semen engendered male offspring, while cold, weak semen produced females (On the Usefulness of the Parts, XIV).

Medieval Islamic and Asian Contributions

In the medieval period, these ideas were transmitted and reinterpreted in both Islamic medicine and East Asian sexual culture.

• Avicenna (Ibn Sina, 980–1037 CE), in his Canon of Medicine, synthesised Aristotelian and Galenic doctrines, asserting that both the strength of semen and the place of its reception in the womb influenced the sex of the child.

• Chinese Daoist manuals, notably The Classic of the Simple Girl (Han–Tang dynasties), proposed that sexual position and penetration depth played decisive roles: deep penetration with the man above favoured the conception of boys, while shallow penetration or female-superior positions were believed to result in girls.

Chromosomal Biology and the Shettles Hypothesis

The discovery of sex chromosomes in the early twentieth century (Stevens, 1905) shifted the conversation from humoral qualities to genetic determinants. Yet older notions of sperm “strength” and deposition continued to resurface.

In the 1960s, Dr. Landrum B. Shettles reformulated these ancient ideas within a modern framework. In How to Choose the Sex of Your Baby (1970), Shettles proposed that:

• Y-bearing sperm are smaller, faster, but more fragile.

• X-bearing sperm are larger, slower, but more resilient.

He recommended specific intercourse techniques:

• For a boy: intercourse close to ovulation with deep penetration, to deposit semen near the cervix and advantage the fast but fragile Y-sperm.

• For a girl: intercourse several days before ovulation with shallow penetration, forcing Y-sperm to perish over distance and favouring the durable X-sperm.

The Modern “Tip”

Shettles’ work crystallised into a widely circulated maxim, often presented in simplified form:

• “To conceive a boy, the husband should ejaculate as deeply as possible within the vagina; to conceive a girl, penetration should be shallow.”

This statement, though couched in modern genetic terminology, resonates with themes already present in Aristotle, Avicenna, and Daoist tradition.

Conclusion

While modern medical science regards the Shettles Method and related practices as unreliable, their intellectual continuity is striking. From Aristotle’s theory of heat and strength, through Hippocratic geography of the womb, Avicenna’s refinements, and Daoist prescriptions on depth and position, to Shettles’ chromosomal reinterpretation, the idea of influencing offspring sex through intercourse technique reflects a persistent human desire to exert agency over biological destiny.

References

Aristotle. (1942). Generation of animals (A. L. Peck, Trans.). Loeb Classical Library. (Original work published ca. 350 BCE)

Avicenna. (1999). The canon of medicine (Al-Qanun fi al-Tibb) (L. Bakhtiar, Trans.). Great Books of the Islamic World. (Original work published ca. 1025)

Dongxuanzi. (2002). The classic of the simple girl (Nvzi jing). In P. R. Goldin, The culture of sex in ancient China (pp. 41–56). University of Hawai‘i Press. (Original text compiled ca. Han–Tang dynasties)

Galen. (1968). On the usefulness of the parts of the body (De usu partium) (M. T. May, Trans.). Cornell University Press. (Original work published ca. 200 CE)

Hippocrates. (2012). On the nature of the child (De natura pueri) (P. Potter, Trans.). Loeb Classical Library. (Original work published ca. 400 BCE)

Shettles, L. B., & Rorvik, D. M. (1970). How to choose the sex of your baby. Doubleday.

Stevens, N. M. (1905). Studies in spermatogenesis. Carnegie Institution of Washington.