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Refutations

The Hadith on Gender Determination — A Scientific Analysis

4 min read 817 words

The hadith on gender determination is raised as a scientific objection to the Prophet ﷺ only by those who read it without understanding the Arabic or the science. The doubt evaporates the moment either of its two valid interpretations is examined against what modern biology actually says.

Sahih al-Bukhari 3329 Grade: Sahih · Bukhari

A man came to the Prophet ﷺ and said: “I came to ask you about something that no one on earth knows except a prophet.” He said: “It will benefit you if I tell you.” The man said: “I will listen with my ears.” He said: “I came to ask you about a child.” He said: “The man’s fluid is white and the woman’s fluid is yellow. When they come together and the man’s fluid overtakes the woman’s fluid, they produce a boy by Allah’s will. And if the woman’s fluid overtakes the man’s fluid, they produce a girl by Allah’s will.” The Jew said: “You have spoken the truth, and you are indeed a prophet.” Then he turned and left. The Messenger of Allah ﷺ said: “This man asked me about what he asked, and I had no knowledge of any of it until Allah brought it to me.”

The Objection

The Claimed Scientific Errors
  1. The hadith attributes a reproductive “fluid” to the woman — but the woman’s egg, not any fluid, provides her genetic contribution.
  2. The only fluid women produce during intercourse is vaginal secretion, whose sole purpose is lubrication — it plays no role in fertilization.

First Interpretation — Vaginal Secretions

Some scholars suggested the woman’s “fluid” in the hadith refers to vaginal secretions, and that the mechanism involves pH levels: if the woman’s acidic secretions dominate, sperm carrying the Y chromosome (male) weaken and X-bearing sperm (female) succeed, producing a girl — and vice versa.

This interpretation is weak for two clear reasons.

Reason 1 — The hadith describes the woman’s fluid as yellow and thin. Vaginal secretions produced during intercourse are white or transparent — not yellow. This is both a matter of sensory observation known to every adult, and confirmed by medical sources. The description does not match.

Reason 2 — The word “preceded” (سبق) in a parallel narration requires a common origin and a common destination. If Ahmed precedes Mohammed in a race, both must have started from the same point heading toward the same goal. Vaginal secretion and male semen come from entirely different sources. The “preceding” language makes no sense applied to them.

Second Interpretation — The Egg and the Sperm

The preferred interpretation: the man’s “fluid” is seminal fluid, and the woman’s “fluid” is the egg (ovum). The phrase “man’s fluid overtakes woman’s fluid” and its parallel “man’s sperm precedes woman’s sperm” refer to which type of sperm — X-bearing or Y-bearing — reaches and fertilizes the egg first.

The Man’s Fluid

Seminal fluid is described as “water” because it is composed of approximately 92–96% water. Sperm cells themselves constitute no more than 2% of ejaculate volume. Calling it “water” (ماء) is scientifically precise.

The Woman’s Fluid — The Egg

The hadith describes the woman’s fluid as yellow and thin (so sperm can penetrate it). These characteristics match the ovum exactly and do not match vaginal secretions at all.

The human egg (ovum) is the largest cell in the human body and is composed primarily of water. It emerges from the Graafian follicle in the ovary surrounded by yellow follicular cells, giving it a distinctly yellow appearance. The zona pellucida — its outer layer — is thin enough for sperm to penetrate.

— Keck Medical Center of USC; eggfreezing.com

The “Preceding” — X and Y Sperm

The parallel narration uses the word سَبَقَ (preceded/overtook). Both X-bearing sperm (producing females) and Y-bearing sperm (producing males) originate from the same source — the man — and race toward the same destination — the egg. The “preceding” language is perfectly accurate.

Sex determination in humans occurs at fertilization. If a Y-chromosome-bearing sperm fertilizes the egg, the child is male. If an X-chromosome-bearing sperm fertilizes the egg, the child is female. The sex of the child depends entirely on which type of sperm reaches the egg first.

This is exactly what the hadith describes — using the word “preceded” — fourteen centuries before the discovery of chromosomes.

Conclusion The Prophet ﷺ described gender determination using two key terms: the color and consistency of the woman’s “fluid” — matching the egg — and the language of racing and preceding — matching X/Y sperm competition. Far from containing scientific errors, the hadith aligns with two distinct facts of modern reproductive biology that were entirely unknown in the 7th century. Allah spoke truthfully: “Nor does he speak from [his own] inclination.” (An-Najm 53:3)
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