If anything, there's been a switch away from complex carbohydrates (grains and starches, particularly) as humans have gained easier and easier access to a wider diversity of foods, including - and particularly - simpler carbohydrates like sugars; the prevalence of fruit and added sugar (especially high fructose corn syrup, but even table sugar, agave, and other objectively-healthier sugar sources) in the modern diet could very well be worth examining as such an "environmental factor".