The leading causes of death have changed markedly over the years. A century ago, infections were the leading causes of death. Today, we will probably survive much longer than our ancestors but it is more likely we will die of age related diseases like mobility problems, arthritis and Alzheimer's or other chronic diseases like heart disease, cancer or stroke.
In a bid to mimic the effects of Parkinson's disease, a London medical research team injected 22 marmoset monkeys with a potent brain poison every day for five days. After the last dose, none was able to move. They sat hunched, mute and rigid in their cages, so severely disabled that they had to be hand-fed. The monkeys were then given the illegal party drug Ecstasy in the hope that it might provide insights into chemical pathways within the brain. None of this research proved beneficial to humans; rendering the suffering of the monkeys valueless. This experiment was part funded by the medical charity Parkinson's UK.