Evolution and environmental change

The effects of agriculture have been to improve the stock by selective breeding at a necessary loss of some capacities to withstand epidemics, while movements of products and stock have increased the speed with which epidemics spread. Some implications are considered. In relation to human genetics there is also evidence of a lack of selection, rather than any directed selection, and this will necessarily have some long-term effects. However, they are not well understood and are certainly slight, but cumulative. All that can be done at present is to maintain the lowest practical exposure to mutagens: the best understood, radioactivity, does not appear to be a serious hazard in the absence of catastrophic events or inappropriate medical usage.