I just read the OP, and just thought I'd say, that some perceived weaknesses in the human body may actually be strengths. I can't find it right now, but in the latest "New Scientist" magazine it described some mutations that may have aided the survival of the Human species. For example, there is a gene mutation that causes haemochromatosis - a condition in which you absorb far to much iron, which deposits in your organs, and you rust to death. (In the very extreme). What was noticed, was that more europeans had haemochromatosis than any other people. This was traced back and it was found that the gene mutation showed significantly in the days of the bubonic plague. Haemochromatosis helped europeans survive through the plague.....
It was a huge strength, but is now rather a weakness isn't it. Also with sickle cell anaemia, the blood cells die and are replaced much faster, preventing the spread of malaria.....