The genomic delay is the lag that exists between our genome, which conditions a physiology and psychology selected to survive in the environment in which the human species evolved, and the artificial world created by culture, with an accelerated evolution that prevents from having the corresponding adaptations selected. This causes in many human beings physical and emotional disorders.
Our genome was selected for more than two million years to become adapted to the Pleistocene, the period in which we became humans. The exclusive characters of our species were selected during this period -corresponding to 99% of the history of the genus Homo, and 95% of the history of our species Homo sapiens- along which our ancestors lived as hunters-gatherers. Although there have been some genetic changes since the beginning of agriculture around ten thousand years ago, these have been quite insignificant. From the anatomical, physiological, and emotional point of view, the Homo sapiens is still a hunter-gatherer. The cultural changes have occurred too fast for us to genetically adapt to them. Our genes have been selected to become adapted to an environment that no longer exists, thus, genes that were useful within the ancient environment in which we evolved can now increase the susceptibility to diseases in the developed world. The different life styles of our hunter-gatherer ancestors and the inhabitants of developed societies cannot be more radical. The environment in which we thrived implied intense physical exercise, food poor in saturated fatty acids, sodium, and sugar, slow cultural changes, and life within small groups in which members received emotional support. On the contrary, the members of developed societies usually have a sedentary life, a diet with excessive saturated fats, sodium, and sugar, chronic emotional stress to which we cannot reply with the fight-flee reactions our evolution has taught us, and social and emotional isolation.
This life style has contributed to a high frequency of cardiovascular diseases, obesity, diabetes, and emotional disorders like anxiety and depression, all of which have become an epidemic in developed societies. The changes of life style can cause epigenetic changes: diminishing physical exercise, the excess of fat, or chronic stress can act as inhibitors of the some gene expressions that can ultimately produce the appearance of chronic emotional disorders, like anxiety and depression, or neuroplastic disorders affecting the learning capacity and memory, and an increase of the oxidative neuronal stress. A better understanding of the environment in which we evolved could help us to have a much healthier life without resigning of the benefits of civilization.