THE defence mechanisms of the human body are so challenging to the concept of evolution that we must spend a little more time considering the implications. We saw in the last chapter that the fail-safe mechanism that prevents blood from clotting inside the body could not have developed gradually over many generations. It had to be there, ready to work, on Day One.

The argument is even more pressing in the case of a broken bone. It is surprising how many people break a bone at some point in their life. Broken bones are extremely painful. They are also potentially lethal. For a time, until the fracture heals, the limb is incapacitated.

Imagine then the horrific consequences if the bone did not mend. Suppose a broken leg stayed broken. You would be unlikely to survive without relying completely on the care of other, equally vulnerable human beings.

It is an amazing fact that a broken bone does repair itself in around six weeks, and so effectively that after a year or two only an expert can identify the position of the original break, so fine is the hairline left after the new bone has formed.

How does it happen? Immediately after a fracture, tiny bone making cells called osteoblasts move into the area of the break. Taking calcium salts from the bloodstream, they arrange themselves in rings or columns, and secrete hard fused shells of calcium phosphate that bind the ends together. A solid lump of new bone, called a callus, swells out and tapers away on either side of the fracture. At this point, the bone cells stop multiplying. In time, as blood vessels and fibres settle down in the repair, special bone-eating cells, called osteoclasts move in and slim down the callus until, for a straightforward fracture, the bone is back to the original shape and strength.

What an incredibly efficient system! If only a motor car repaired itself automatically every time it was involved in an accident! Yet our skeletons mend themselves, just like that. The bone cells move in, multiply, stop multiplying, then slim down the repair without us even thinking about it.

Now ask yourself, how could such a system arise by natural selection? The very first vertebrate to break a big bone would be fatally incapacitated unless the repair system is already there and working. Yet according to evolutionary theory, the system cannot develop quickly. And an incomplete system is useless. If bone cells started growing randomly anywhere in the body, this would be fatal. If they happened to burrow into recent fractures, they could hardly be expected in the early days to join up the ends thoroughly enough to bear a load. Yet a wobbly mend would have no evolutionary advantage over no mend at all. The animal would be unable to move about. And even assuming a repair started in the right place at the right time, if it did not switch off once the gap was sealed, the callus would go on growing bigger and bigger threatening the animal’s life.

All told, it is more logical to believe that a Designer put together a framework for the body that was light and strong, reinforced with fibers for shock resistance, and built from minerals readily available in the diet; and that He foresaw how a sudden overload could cause a break, and therefore built in an automatic repair system to prevent widespread and premature loss of life. Must we not echo, once again, the Psalmist who wrote, “I am fearfully and wonderfully made” (Psalm 139:14)?