Up until the last few seconds of human history, it was collectively accepted that sex is binary. People are born either male or female. Not so today. Many biologists and psychologists tell us sex is on a spectrum or there are more than two sexes. As a result, popular-level publications push this new narrative. USA Today, for example, tweeted that there are “three different types of sexes.” Egale, a Canadian LGBT advocacy group, teaches kids in clever rhyme that, when it comes to men and women, “you can be both or a mix of the two, or you can be neither if that’s what suits you.”
To most people, however, these new claims are at odds with common sense. Still, many wonder if they’re missing something. Has there been a new discovery that tosses out what we know about human sexuality? No.
Though it seems that pockets of our culture are confused about what we are, there’s no excuse for Christians to be bewildered. Our Maker tells us through Scripture (special revelation) and creation (general revelation) how he made humanity.
Scripture tells us that our Maker made humans male or female. In his defining creative work of humanity, “God created man in His own image, in the image of God He created him; male and female He created them” (Gen. 1:27). Notice that when God begins the human race, he creates only two sexes. Jesus also attests to this truth when he cites this Genesis account of creation: “Have you not read that He who created them from the beginning made them male and female…?” (Matt. 19:4). Scripture teaches that our Maker made only males and females, and it never acknowledges the existence of any other sex. This has been theologically univocal for thousands of years. God tells us how he made us through another source, though.
The created world (studied through science or other means) also tells us that humans are only male or female. While pursuing my degree in physical therapy during the 1990s, my professors taught me that human sexuality is binary. Though they weren’t Christians (one was an outspoken atheist), they taught what they observed to be true from nature. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). The Y chromosome contains a “male-determining” gene called an SRY gene. It signals to the developing human embryo to create a penis and testicles. Without an SRY gene, the embryo develops a vagina and ovaries. This has been understood since its discovery by biologist Nettie Stevens in 1905.
Gender ideology advocates interrupt at this point. Not all males are XY, and not all females are XX, they say. Some people are born intersex, a term that covers a broad range of chromosomal or anatomical variations that affect a person’s sex characteristics. Some people are born XXY, XXYY, or XYY. Sometimes, the SRY gene isn’t on the Y chromosome. Sometimes, physical differences in a person’s sexual anatomy preclude them from fitting neatly in a male or female category. There’s an endless list of examples. Here’s their point: the many chromosomal and anatomical variations are evidence that sex is not binary—it’s not as simple as male or female. Though there are many mistakes with this thinking, here are four reasons why we know sex is binary.
First, while it’s true that intersex people are born with chromosomal or anatomical variations, the vast majority of them are obviously male or female. According to the Intersex Society of North America (ISNA) only around 0.05% of people are born with ambiguous genitalia, requiring a specialist to intervene. Most intersex people appear and function as either male or female. There’s no ambiguity. Furthermore, just because a person is intersex, that does not mean they identify as transgender. These are two different things. Even the ISNA admits that “the vast majority of people with intersex conditions identify as male or female rather than transgender.”
Second, variations in sex characteristics don’t nullify the norm. While it’s true that there are many possible chromosomal and anatomical differences, it doesn’t follow that sex is not binary. Intersex people don’t represent a third sex or prove sex is on a spectrum. A nickel, for example, only has two sides. According to some research, though, it will land on its edge 1 out of 6000 times when tossed. Does that mean a nickel doesn’t have only two sides? No, because exceptions don’t invalidate the rule. Humans have two arms, though some are born without one or both. That, however, doesn’t negate the fact that humans are two-armed beings. Some people are born with three copies (instead of two) of chromosome 21 (trisomy 21, AKA Down syndrome). That doesn’t negate the fact that humans should only have two copies of chromosome 21. In the same way, humans can be born with different anatomical or chromosomal variations (XXY, XXXY, etc.) that affect their sexual anatomy and physiology, but these represent natural variations within the male and female sexes.
Third, we know there are only two sexes because there are only two possible sex cells (sperm or egg). Human males are those whose sexual anatomy is organized around the production (and delivery) of sperm. Human females are those whose sexual anatomy is organized around the production of eggs. That’s it. There are no other possible sex cells in existence. That’s why we know there are only two sexes. There is no person on earth who can produce a sex cell that isn’t either a sperm or an egg. Furthermore, no one can produce both. Though some may be incapable of producing one or the other (due to prematurity, advanced age, or a developmental anomaly), that doesn’t disqualify the norm that human beings are made to produce either one of two sex cells: sperm or egg.
It's worth noting that every person who exists today—whether gay, straight, cis, trans, intersex, etc.—was created by the union of two sex cells: a sperm and an egg. There’s no other possible cell that can be involved in the production of a new human being. There are only two sexes because there are only two types of sex cells.
Fourth, we know there are only two sexes because human bodies are made for two-sex intercourse. Everything we know about the male and female sex organs tells us that these two body systems are complementary. They not only fit together, but they function together. It’s obvious that the parts fit because when brought together in a male-female sex act, everything is suitably sized and perfectly shaped for one another. That’s only half of the story, though.
These parts function together. The male and female reproductive organs are part of the only body system that requires a separate body of the opposite sex to fulfill its ultimate function. Sperm and egg, left within the testicles or ovaries, will never meet their full potential until they’re brought together in male-female sexual intercourse. This process requires exactly two (not one, three, or any other combination) different human sexes to complete.
Does this evidence mean we can immediately classify every human being as male or female when they’re born? No. It’s true that in rare circumstances it might be difficult to know because their chromosomes or anatomy might make it unclear. That, however, does not mean the person might be both, neither, or some third sex. Difficulty in classifying someone as male or female does not render our biological knowledge of the sexual binary suddenly invalid.
Does this mean we don’t value or care for a person with a chromosomal or anatomical variation? No. Children born with Down syndrome (a chromosomal anomaly), for example, are still made in God’s image, intrinsically valuable, and deserving of our love, care, and compassion. The same is true for every intersex person. They, too, are made in God’s image, intrinsically valuable, and deserving of our love, care, and compassion. Just because we don’t adopt a radical redefinition of sex classification, that doesn’t mean we don’t care about men and women—many of whom may be our friends and family—who have intersex conditions. Though that’s how the culture likes to paint Christians, in reality we deeply care for them.
We’re not denying that people with intersex conditions exist. Nor are we denying that transgender people identify as something other than their biological sex. We can affirm the reality of these people and their experience while simultaneously affirming there are only two sexes. These are not mutually exclusive.
What we can’t do, however, is deny what appears to be the reality regarding human sexuality: there are only two sexes—male and female. We know this from Scripture and creation. God has spoken clearly through both revelations. Let’s hold fast to this truth but make sure we also uphold the value and dignity of people born intersex or who identify as transgender.