No, bad design does not prove there is no creator, but does raise a question about why there is bad design in the first place. On the other hand, less than optimal design (meaning, vestigial organs and flaws) is a prediction that is made and confirmed by evolutionary theory.
There are a lot of serious flaws in the "design" of the human species. I don't know them all off the top of my head, so I did a little research and found this list. I'll discuss vestigial organs in a bit.
- The female pelvis is too small for the baby's head. This can make birth difficult and cause a lot of prenatal damage to the child, as well as potentially hurt or kill the mother.
- The blood vessels that lie in front of the retina are prone to damage and can lead to blindness.
- Wisdom teeth that can develop secondary abscesses (a pus filled cavity), which can infiltrate the cranium and cause brain abscesses, meningitis, and epidural empyemas.
- The high position of the larynx can lead to choking deaths due to the cartilage rings that surround it.
- The Odontoid process, an extension of the C2 vertebrae can easily fracture, leading to death and paralysis, as well as the inability to breathe without a machine.
- The semi-soft disc material between vertebrae were great for quadrupeds, but in humans they can easily compress due to upper body weight and cause trauma.
- Hip joints are not perfectly suited to supporting human weight (they are better suited for quadrupeds). The stress can cause hip degeneration, femoral neck fractures in women and the elderly. This doesn't happen in quadrupeds.
- Tibial cartilage in the knees is not strong enough for human weight, and can lead to knee problems in life. Once again, this doesn't happen in quadrupeds.
- Foot and ankle bones are better adapted to walking on the toes, as it causes a more even weight distribution. Human weight can cause the arches between them to collapse as weight is not evenly distributed.
- The median nerve that runs through the Carpal tunnel is covered by tough ligaments. The wrist is necessary to extend in order to achieve maximum flexion by the fingers. The problem is, repetitive use and minor injuries can cause the nerve to come in and out of the Carpal tunnel, causing problems with hand function.
- The Ulnar nerve does not go in front of the elbow and rest in the softer tissue, instead it forms on the outside. In older mammals, like horses, this isn't such a big deal since their elbows don't flex, but because ours do it can compress and overextend the nerve.
- The urethra, vagina, and anus are all located in such a close proximity that infection from the rectum can travel to the uterus, bladder, or kidneys and cause serious conditions.
- The plantar nerves run from under the ankle and course under the foot to the metatarsals. Uneven weight distribution can cause arches to fall (as discussed earlier), and compress those nerves. This does not happen in older mammals, such as cats or dogs.
- The appendix is prone to infection which causes it to rupture. This can be life threatening.
- The large veins in the leg dilate because they are needed for walking, running, standing, etc. But, extended sitting can cause the blood to clot, which the veins usually send to the heart and lungs and causes pulmonary emboli. Many humans, but no older mammals, die from this.
- The Venous Cavernous sinuses contain veins, arteries, and important nerves (those for eye movement and sensations). When a clot develops due to their close proximity, it can put extreme pressure on the nerves.
- Infections are also frequently found in the skull sinuses, which cause a lot of deaths in children.
- Congenital birth defects due to ancestral DNA. Gill slits in the embryonic stage can leave remnants which develop abscesses and cause pain. Another is chordoma, a cancer that forms in the notocord tissue. The notocord is an ancestral feature which gets absorbed by the bony spine. Sometimes, notocord which isn't entirely absorbed can form tumors at the base of the brain.
- Some babies are born with mutations that cause the baby's blood to contain the wrong Rhesus antigen. This can cause the mothers body to try to destroy the baby.
Evolution is not perfect. If something fails, it can't start over with a new design, it has to work with what it has. This is because it's not a sentient being; it doesn't think and consciously make decisions like whether or not to add a gene there, or take away one here. Design aspects that are not perfect cannot just be removed and the process begun again, they have to be naturally selected for. Unfortunately, because it is not sentient, those design aspects that don't necessarily cause death in all cases are often passed on. Those flaws are hard to get rid of when they don't cause the species to become extinct. Evolution is not perfect in this respect.
Think of our bipedalism. The ability to walk upright was a great mutation. It allowed us to evade predators, find food, move quicker, and even see over longer distances, but the imperfect processes that created it could not have possibly anticipated the problems associated with it (including the uneven weight distribution). Natural selection isn't going to select for it because, on the whole, bipedalism still allows for greater survival.
Evolution also predicts vestigial features (essentially, a feature that is no longer needed but has not disappeared from the genome). Vestigial features do not appear in all humans, but that depends on how old they are. Evolution cannot permanently delete parts of the genome, so these features can exist in creatures a million years later due to their ancestral DNA; these features are just buried and unlikely to come out. Nevertheless, those ancestral features that rarely come out are still vestigial. Some vestigal organs are listed below:
- Vomeronasal Organ
- Extrinsic ear muscles
- Wisdom teeth
- Neck rib
- Third eyelid
- Darwin's point
- Subclavius muscle
- Palmaris muscle
- Male nipples
- Erector pili
- Body hair
- Thirteenth rib
- Plantaris muscle
- Male uterus
- Fifth toe
- Female vas deferens
- Pyramidalis muscle
- Paranasal sinuses
So, now that we have some background, let's go to what AiG specifically claims. They begin by asking the question, "how can humans judge what is optimal design?". This question has a simple answer: because it would be OPTIMAL. If it causes major health issues, including death, chances are it's not the optimal structure. How about those extraneous vestigial features? Those are not needed and don't necessarily perform any particular function, yet we still have them. This is not OPTIMAL, it's inefficient and wasteful. Sure it works, but so does paying for a 20 dollar meal with a 50 dollar bill. It's not the optimal payment (because it requires change), but it works.
The second thing AiG says is outright stupid. They expect a world cursed with degeneration for 6000 years not to be able to maintain optimal design. Besides the fact that the earth is obviously not 6000 years old and that over time we are not deliberately degenerating, I was under the impression that humans couldn't judge what is optimal? Apparently AiG can.
I'll wrap this up by restating what I mentioned earlier. Evolution can't just restart it's design when something doesn't work in nature. It has to stick with modifying what it has. Sometimes, though, design flaws that don't always cause death (but can still cause problems) can't be selected for and removed from the species. Thus is the nature of the beast.
It doesn't necessarily prove that God doesn't exist, but it does prompt a question: why did God fuck up so badly?