Question

According to the Centers for Disease Control and Prevention (CDC), obesity in the U.S. population increased from about 12% in 1991 to about 34% in 2006. The highest increase occurred in 18- to 29-year-olds. Although part of the reason is our increasingly sedentary lifestyle, the principal cause is our overconsumption of abundant processed food products, many of which are high in fat and sugar content. Why do you think fat tastes good to so many people, and is difficult to resist? Consider the fact that our appetites and digestive systems evolved over time under very different circumstances. Are there advantages to our tendency to eat too much that would have been selected for in the course of human evolution? How can we, as a society, deal with the problem?

Answer 1

1.Fat concentrates smells and flavors in food. It gives foods a smooth creamy texture that most of us enjoy. Since fat gives us more energy than proteins or carbohydrates, it makes us feel full faster. This makes our brains release serotonin hormones that makes us feel content.

2.

Follow-up investigations indicate as well that foods eaten by humans today, especially those consumed in industrially advanced nations, bear little resemblance to the plant-based diets anthropoids have favored since their emergence. Such findings lend support to the suspicion that many health problems common in technologically advanced nations may result, at least in part, from a mismatch between the diets we now eat and those to which our bodies became adapted over millions of years. Overall, I would say that the collected evidence justifiably casts the evolutionary history of primates in largely dietary terms.

TTHEstory begins over 55 million years ago, after angiosperm forests spread across the earth during the late Cretaceous (94 million to 64 million years ago). At that time, some small, insect-eating mammal, which may have resembled a tree shrew, climbed into the trees, presumably in search of pollen-distributing insects. But its descendants came to rely substantially on edible plant parts from the canopy, a change that set the stage for the emergence of the primate order.

Natural selection strongly favors traits that enhance the efficiency of foraging. Hence, as plant foods assumed increasing importance over evolutionary time (thousands, indeed millions, of years), selection gradually gave rise to the suite of traits now regarded as characteristic of primates. Most of these traits facilitate movement and foraging in trees. For instance, selection yielded hands well suited for grasping slender branches and manipulating found delicacies.

Selective pressures also favored considerable enhancement of the visual apparatus (including depth perception, sharpened acuity and color vision), thereby helping primates travel rapidly through the three-dimensional space of the forest canopy and easily discern the presence of ripe fruits or tiny, young leaves. And such pressures favored increased behavioral flexibility as well as the ability to learn and remember the identity and locations of edible plant parts. Foraging benefits conferred by the enhancement of visual and cognitive skills, in turn, promoted development of an unusually large brain, a characteristic of primates since their inception.

As time passed, primates diverged into various lineages: first prosimians, most of which later went extinct, and then monkeys and apes. Each lineage arose initially in response to the pressures of a somewhat different dietary niche; distinct skills are required to become an efficient forager on a particular subset of foods in the forest canopy. Then new dietary pressures placed on some precursor of humans paved the way for the development of modern humans. To a great extent, then, we are truly what we eat.