The faults in the design of the human eye, especially, show its evolutionary origins.  [See eye diagram of retina.] When we study the retina at the back of the eye, we can see that the cell layers are backwards.  Light has to travel thru seven layers of cells before reaching the light sensing cells.  Then the signals go back thru these layers to the nerves on the inside surface.  In addition, the blood vessels are on the inside surface and further block the light.  A truly intelligent designer could have done better than the human eye.  Actually, evolution did a better job with the eyes of birds (which have no blood vessels in the retina) and the octopus and squid (which have the light sensing cells on the surface).

In fact, vision is so useful for survival that eyes have evolved independently at least twenty separate times, with at least a dozen different designs.

Humans and other animals have many more examples of sub-optimal or bad design.  Here are a few:

• One of the worst designs in mammals is the nerve for the larynx, called the recurrent laryngeal nerve.  It is much longer than it needs to be — going from the brain into the chest, around the aorta, and back up to the larynx.  In humans it's about three feet long, but in giraffes it's about fifteen feet longer than needed.

• The human pelvis slopes forward, which was useful for our knuckle-walking ancestors.  The only reason that we can walk upright is because we have an incredible sharp bend at the base of our spines (which is the source for so much low back pain).  Our abdominal organs are even suspended from the spine, which is just a vestigial holdover from when the spine was actually above them.

• The human baby's skull is too big, such that many women die in childbirth if they don't get modern medicine.