Every day biomedical researchers are making progress in understanding how defects in the molecular processes within our cells lead to processes like aging, illness and death. But we will never be completely disease-free. Humans and every organism around us will continue to evolve, and new pathogens will always arise that can infect us. Existing strains of bacteria and viruses will occasionally develop new forms that are resistant to current treatments and require the development of new ones. Our children will continue to inherit particular forms of genes that increase their risk of developing some diseases and decrease it in other cases. Our cells will continue to experience unpredictable changes such as mutations that cause cancer or other problems for our bodies. Humans will continue to make new substances that enter the environment and might, over the long term, have unforeseeable, adverse effects on our health. We will continue to be exposed to toxins that arise, for example, from pollution. Our bodies may be able to cope with such “environmental loads” for decades, but as we live longer and longer, we may discover that they have a cumulative effect which only causes problems at extremely advanced ages.
Russ Hodge, science writer at the Max Delbrück Center for Molecular Medicine, answered this question.