Dietitians, nutritionists, and the fats and oils industry have all apparently succumbed to the near-panic generated by reports that hydrogenated fats containing trans acids will alter the HDL/LDL cholesterol ratio in human blood lipids in a way presumed to create a greater risk of heart attacks. The fact that bacterial and plant trans fatty acids have always been a part of the diets and biochemistry of the lower animals that evolved over billions of years into humans, at least several million years ago, is ignored. In terms of evolution we actually followed the same diets until very recently, with ruminant fats regularly contributing up to 5%trans acids in the fats eaten by hunters and later in foods for most agriculturists. The Canadian beaver living on a diet rich in cellulose, has recently been discovered to deposit trans acids in its depot fats. The proposed increase in fiber in our diets may similarly change our intestinal microflora and create more trans acids. Are they absorbed? Are they really hazardous? Are all these sudden changes in dietary recommendations really necessary when the lifespan of the well-fed western peoples steadily increases?