The Ability of Cells to Specialize

When you were conceived, you began life as one tiny cell called a zygote, barely large enough to be seen by the naked eye. And yet, several months later, you were a fully formed baby. That one cell multiplied and changed into over 200 different types of cells with various shapes, sizes, and functions.

Consider: A zygote makes a copy of its DNA and divides in two. The resulting cells repeat this process numerous times. At first, all the new cells are basically identical. In their DNA, they have all the instructions needed for making every type of cell.

One week after conception, the cells begin to specialize into two kinds. Some cells will become the embryo, while other cells will become the placenta and related tissues that help the embryo to grow.

By the third week, the cells of the embryo organize into three layers. Those in the outer layer will eventually specialize into nerve, brain, mouth, outer skin, and other cells. The cells of the middle layer will become blood, bones, kidneys, muscles, and other tissues. The inner layer cells will become internal organs, such as the lungs, bladder, and much of the digestive system.

Throughout the pregnancy, some of the cells migrate—individually or in groups—from certain areas of the embryo to other areas. Other cells group together and form sheets or fold over into cords or cavities. These processes require remarkable coordination. For example, at one point, sheets of cells curl themselves into little tubes. This happens simultaneously in various places throughout the embryo. The tubes then begin to lengthen and branch out, eventually joining to produce a complete circulatory network.

By the time a healthy baby is born, its hundreds of billions of cells have all specialized into the correct type, in the correct location, and at the correct time.

What do you think? Did the cell’s ability to specialize evolve? Or was it designed?