How does a fertilized egg become a human?
Imagine that you place a 1-inch-wide black cube in an empty field. Suddenly the cube makes copies of itself - two, four, eight, 16. The proliferating cubes begin to form structures - enclosures, arches, walls, tubes. Some of the tubes turn into wires, PVC pipes, structural steel, wooden studs. Sheets of cubes become wallboard and wood paneling, carpet and plate-glass windows. The wires begin connecting themselves into a network of immense complexity. Eventually, a 100-story skyscraper stands in the field.
That’s basically the process a fertilized cell undergoes beginning with the moment of conception. How did that cube know how to make a skyscraper? How does a cell know how to make a human (or any other mammal)? Biologists used to think that the cellular proteins somehow carried the instructions. But now proteins look more like pieces of brick and stone - useless without a building plan and a mason. The instructions for how to build an organism must be written in a cell’s DNA, but no one has figured out exactly how to read them.
- Steve Olson, author of Mapping Human History
For you created my inmost being;
you knit me together in my mother's womb.