[Explaining why God, who despite designing humans and chimps 95% genetically identical, gave chimps <a href="http://www.abc.net.au/news/newsitems/200509/s1451085.htm" target="_blank">a gene resistent to Alzheimer's disease</a> but didn't give those same genes to humans.]

Normal planets evolve to the point where a final modification of the DNA creates the first true humans. They are allowed to procreate, and when they have sufficient numbers, a final DNA “boost” is given which protects against most diseases and other maladies. Unfortunately, our little planet had a rebellion problem, and the “boost” was incomplete, leaving us with many problems. This is being addressed, but from a different direction, and will take time to resolve.