After 300-400 million years evolution from the stone age. Human'sbody is not as perfect as we think. 

Human beings is described as the most wonderful body designed by our genes. But we should know there are many shortcomings of our body parts. And some of them would make us weak, some of them can bring us disease. 

First, too many teeth. As one of omnivorous animals, we have 32 teeth.But in our life time, there are only 28 is useful. And the other 4 teeth usually bring us a lot of pain. We may need to pay dentist to pull them off. 

Second, there is space between the rib. And the rib is not enough. As we know the most important organs of our body is inside the chest. There used be some protection to these organs. So during our evolution, we own the ribs. But the rib the space. This can not protect the organs. And also because it is not strong enough. The rib sometimes can be harmful when it is broken. It would cause internal haemorrhage inside our chest.

Third, male's testis is in the outside of our trunk. It is just covered with one piece of skin. As we know it is one important reproductve oragn. But it is not protected by our body parts. It is one weakness of our body. And it also would influence the sperm quality. It is one important part of human being in the world. But it is not protected.

Fourth, the long neck. We all treat the long neck as one kind of beauty of our body. But it is also one weakness. The nerve system and important vessel are inside this not protected neck. It is easy to get hurt. And this hurt might be deadful to our life. 

Fifth, the spinal is easy to get hurt. We treat bipedalism is one signature of our evolution. But this evolution have broughta lot of stress to the spinal. This stress make 80% of people have the pain. If our spinal have a better shape. We may prevent this pain.