This question, while amusing, is often asked by children. It’s a valid question. I don’t know the answer for sure for two reasons:
I’ve never met Adam and so this isn’t something I’ve seen for myself.
The Bible doesn’t answer this question directly.
But we can engage in some reasonable speculation. This is the story of Adam’s creation according to Genesis 2:7. “The LORD God formed the man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being.” And then God created Eve. “Then the LORD God made a woman from the rib he had taken out of the man…” (Genesis 2:22).
Our navels come from our time in the womb when we needed nourishment from our mothers through the umbilical cord. But God created Adam and Eve as full-grown adults. Therefore, I think it’s reasonable to conclude that Adam and Eve did not have bellybuttons because they didn’t need them. It makes me smile to imagine their children pointing at their own bellies and saying, “Dad, how come you don’t have one of these?” Then Adam would tell the story of his own creation, teaching his children where we all come from.
This question leads us to the more important one: “Who made me?” And the answer is quite clear. “Then God said, ‘Let us make man in our image, in our likeness, and let them rule…over all the earth, and over all the creatures that move along the ground.’ So God created man in his own image, in the image of God he created him; male and female he created them” (Genesis 1:26-27). Out of all God’s creatures, it is only human beings that were created in God’s image.
Human beings are the crown of God’s creation. When you think about the magnificence of God’s creation, that is a wondrous thought. “When I consider your heavens, the work of your fingers, the moon and the stars, which you have set in place, what is man that you are mindful of him, the son of man that you care for him? You made him a little lower than the heavenly beings and crowned him with glory and honor. You made him ruler over the works of your hands; you put everything under his feet…” (Psalm 8:3-6). God made us in his own image. He made us like him so that we reflect and represent him to the world. This is a great privilege and an awesome responsibility.
God made you, body and soul, exactly as he wanted you. David knew that. “For you created my inmost being; you knit me together in my mother’s womb. I praise you because I am fearfully and wonderfully made; your works are wonderful, I know that full well…”(Psalm 139:13-14). You are fearfully and wonderfully made. Praise the Lord for that today!