I have always wondered if we have beaten natural selection or do we just think we have. Humans have advanced science and invented medicines and producers to cure disease and extend human life by decades. We have not natural predators and our population is unstoppable. It seems like the pressures of the natural world have very little impact on who succeeds in our world and who doesn’t. It’s about money and beauty- right?
That might not be true. Ten to 15% of couples in Western Countries experience difficulties getting pregnant. Of those 30-40% of the issues are associated with each gender and the rest is a combination of issues that are not fully understood yet. Women’s fertility is well researched. Birth control is the most researched drug ever. However much less is known about men’s fertility.
Researchers at the Fertility-Assisted Fertilization Centre in Brazil recently investigated lifestyle choices impacts on male fertility. The results show that sperm quality is linked to lifestyle choices. Higher fruit and grain diets led to increased sperm motility. Also, men that drank alcohol and/or were overweight had lower sperm counts and less motile sperm. These lower quality sperm resulted in men that drank more alcohol and ate more red meat had lower conception rates, compared to men that at more vegetables.
Overall fertility and semen quality have declined in the past few decades. The scientist believes lifestyle changes are linked to increased obesity and exposure to toxins and pollutants. Lower fertility rates and semen quality means that it is harder for those men to pass on their genes. That is the definition of biological fitness the ability of a genotype or phenotype to survive and reproduce in a given environment.
This could mean that after centuries of selecting for a preference of sweet and fatty foods, that in future generations (no time soon), that humans will have preference for lower calorie foods, because the environment has changed. The ability to store fat is no longer biological beneficial, when food is abundant.