As, therefore, the wisdom of this world is foolishness with God, it follows that we cannot be wise in the sight of God, unless we are fools in the view of the world. — John Calvin 
As we can see from the world around us, men and women are different. But how are we different? Our bodies have obvious differences, but what about our personalities and interests? Anyone who has spent time with children can tell you that boys and girls tend to play and interact in distinct ways. From comparing notes with friends, I can confirm that raising a household of boys is not the same as raising a household of girls.
From our observations, we can make generalizations about men and women, boys and girls. Men tend to be physically bigger and stronger. Women tend to be smaller and physically vulnerable. Boys may prefer playing with cars and tend to turn any household object into a weapon. Girls may like playing with baby dolls and pretending to be a mommy.
We are also aware of cultural expectations of how men and women, boys and girls, should behave and dress. These cultural guidelines differ over time and from culture to culture. What was appropriate for a 5th Century Chinese woman is not necessarily the same for a 21st Century American woman.
While we acknowledge such generalizations and cultural expectations for men and women, we must be careful how we apply them to our beliefs about gender. Size and strength vary among men and women, and so do our preferences, personalities, and interests. These generalizations and expectations are not essential to our being as men and women. A muscular woman is still a woman. A man who is shorter than his wife is still a man. A girl who plays with cars and stick swords is still a girl. And a boy who plays with dolls pretending to be a daddy is still a boy.
It’s also important to recognize the limitations of what we can learn from the world around us. We live in a fallen world that bears the scars of sin and death. The world is often harsh and cruel, where the strong dominate the weak and where self-preservation and self-advancement are the status quo. As Tennyson wrote , “nature red in tooth and claw.”
Our ability to understand and apply what the natural world teaches us is limited even where it displays the glory of God and of His creation. Not only is the world fallen, but so are we. Our bodies, our minds, our ability to reason, all are affected by sin. As Paul writes in Romans 1:18-25, all humanity sees the evidence of God in the things that are made and the call to worship Him, and yet, all reject Him and worship creation instead. Our foolish hearts are darkened. And we would have remained in our darkness, if not for His merciful intervention in our lives.
Thankfully He has not left us in our sin and darkness. He has redeemed us by the blood of the Son and opened our eyes and hearts through the work of the Spirit. He has also given us His word in the Scriptures so that we can understand who He is, who we are, how we are saved, and how we are to worship Him and serve each other. All of our observations from the natural world have to be read through the lens of Scripture.
Scripture tells us that God is eternal, without beginning or end. He is the Creator of all things. We are His creation, and we were created to worship Him. We are made in the image of God, as I wrote in Beyond Authority and Submission:
In our very nature, men and women are equally made in the image of God. This is who we are. There is a profound unity in humanity. You and I, and everyone else, come from the first man, Adam. Even Eve was created from Adam. We have the same human nature, no matter what country we’re from or what our bodies look like on the outside. That unity is what Adam emphasized when he first saw Eve: “This is now bone of my bones, and flesh of my flesh” (Gen. 2:23). 
Having the same human nature doesn’t mean that all humans are exactly the same. There is considerable diversity within humanity, but we are all made in His image. We are all human beings descended from Adam.
Because we are all descended from Adam, we have all inherited Adam’s fallen, sinful human nature. When Jesus was born, He took on our human nature in His incarnation. Jesus has both a human nature and a divine nature. As the confessions and catechisms teach, He had to be both God and man to be our Mediator and Savior. 
That’s why we must acknowledge that men and women have the same human nature. All humanity is united in Adam, and all believers (male and female) are united in Christ (1 Cor. 15:22). There are serious consequences of asserting that men and women have separate natures. If men and women don’t have the same human nature, then did Christ die as a human or as a male? If He died only as a male, then how are women saved? As Gregory of Nazianzus summarized , what is not assumed by Christ in His incarnation (in this discussion, a female nature), can’t be redeemed by His life, death, and resurrection.
Scripture makes a distinction between God and man, between Divine and human nature. It distinguishes between sinful human nature (according to the flesh) and redeemed human nature (according to the Spirit). But it does not divide human nature into a male nature and a female nature.
The world around us may show us that men and women are different. But Scripture teaches us who and what we are. Men and women made in the image of God and redeemed by the blood of the Lamb. We are the body of Christ and called to pursue Christian virtues: the fruit of the Spirit and the armor of God. We must serve God and each other, not as the world would have us to do, but out of brotherly love for each other:
Do nothing from selfishness or empty conceit, but with humility of mind regard one another as more important than yourselves; do not merely look out for your own personal interests, but also for the interests of others. (Phil. 2:3-4)
We, men and women, are more alike than we are different. While we celebrate the beauty of those differences, we should remember what unites us.
  Rachel Green Miller, Beyond Authority and Submission: Women and Men in Marriage, Church, and Society , 37.