Posted on 11/19/2002 12:54:45 PM PST by PatrickHenry
We humans are strange primates. We walk on two legs, carry around enormous brains and have colonized every corner of the globe. Anthropologists and biologists have long sought to understand how our lineage came to differ so profoundly from the primate norm in these ways, and over the years all manner of hypotheses aimed at explaining each of these oddities have been put forth. But a growing body of evidence indicates that these miscellaneous quirks of humanity in fact have a common thread: they are largely the result of natural selection acting to maximize dietary quality and foraging efficiency. Changes in food availability over time, it seems, strongly influenced our hominid ancestors. Thus, in an evolutionary sense, we are very much what we ate.
Accordingly, what we eat is yet another way in which we differ from our primate kin. Contemporary human populations the world over have diets richer in calories and nutrients than those of our cousins, the great apes. So when and how did our ancestors' eating habits diverge from those of other primates? Further, to what extent have modern humans departed from the ancestral dietary pattern?
Scientific interest in the evolution of human nutritional requirements has a long history. But relevant investigations started gaining momentum after 1985, when S. Boyd Eaton and Melvin J. Konner of Emory University published a seminal paper in the New England Journal of Medicine entitled "Paleolithic Nutrition." They argued that the prevalence in modern societies of many chronic diseases--obesity, hypertension, coronary heart disease and diabetes, among them--is the consequence of a mismatch between modern dietary patterns and the type of diet that our species evolved to eat as prehistoric hunter-gatherers. Since then, however, understanding of the evolution of human nutritional needs has advanced considerably-- thanks in large part to new comparative analyses of traditionally living human populations and other primates--and a more nuanced picture has emerged. We now know that humans have evolved not to subsist on a single, Paleolithic diet but to be flexible eaters, an insight that has important implications for the current debate over what people today should eat in order to be healthy.
To appreciate the role of diet in human evolution, we must remember that the search for food, its consumption and, ultimately, how it is used for biological processes are all critical aspects of an organism's ecology. The energy dynamic between organisms and their environments--that is, energy expended in relation to energy acquired--has important adaptive consequences for survival and reproduction. These two components of Darwinian fitness are reflected in the way we divide up an animal's energy budget. Maintenance energy is what keeps an animal alive on a day-to-day basis. Productive energy, on the other hand, is associated with producing and raising offspring for the next generation. For mammals like ourselves, this must cover the increased costs that mothers incur during pregnancy and lactation.
The type of environment a creature inhabits will influence the distribution of energy between these components, with harsher conditions creating higher maintenance demands. Nevertheless, the goal of all organisms is the same: to devote sufficient funds to reproduction to ensure the long-term success of the species. Thus, by looking at the way animals go about obtaining and then allocating food energy, we can better discern how natural selection produces evolutionary change.
Becoming Bipeds
Without exception, living nonhuman primates habitually move around on all fours, or quadrupedally, when they are on the ground. Scientists generally assume therefore that the last common ancestor of humans and chimpanzees (our closest living relative) was also a quadruped. Exactly when the last common ancestor lived is unknown, but clear indications of bipedalism--the trait that distinguished ancient humans from other apes--are evident in the oldest known species of Australopithecus, which lived in Africa roughly four million years ago. Ideas about why bipedalism evolved abound in the paleoanthropological literature. C. Owen Lovejoy of Kent State University proposed in 1981 that two-legged locomotion freed the arms to carry children and foraged goods. More recently, Kevin D. Hunt of Indiana University has posited that bipedalism emerged as a feeding posture that enabled access to foods that had previously been out of reach. Peter Wheeler of Liverpool John Moores University submits that moving upright allowed early humans to better regulate their body temperature by exposing less surface area to the blazing African sun.
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Well, then why is everyone worried about what we eat now? Our bodies should just evolve to better handle the Big Macs, large fries and giant chocolate shakes.
My fourth grade health book -- printed during the Pleistocene -- recommended eating a wide variety of foods. Has something changed?
Actually, I've been occupied elsewhere, with another literalist who seems to have taken it as his personal mission to drive the Roman Catholic vote away from the Republican Party. Sure hope the next evangelical revival goes well, because given their rein, these guys could get the conserative vote to, oh, let's say, maybe as high as 15%.
...I think is the primary answer, though not necessarily contrary to that posed here, which would theorize some semblance of mechanism.
The problem is that medical science is preventing that step in human evolution. If they keep on doing heart bypass operations to save people, then the genetic superiority of those who can survive "Super Sizing" their fast food meals cannot be exploited. However, if Hitlery takes over the country's medical system and drives it into the ground, people will no longer be able to survive their heart attacks.
Please look for my book "All I really needed to know about eugenics, I learned at McDonalds" coming to bookstores and drive-thrus near you.
The author completely misses two boats:
1) Our brains as well as other genetic development really took off upon the invention of war, which is in effect high-speed evolution. If you match two tribes together in a battle, the smartest tribe usually wins. That is the reason our brains grew. Darwin knew this, yet modern liberal university professors are in denial because it doesn't fit in with the socialist utopian / narcissistic view of humans.
2) The author didn’t even read Atkin’s diet book, else would have learned that matching calorie intake to calorie consumption is an oversimplification. The author is too deep into the world is flat community that he can’t bring himself to realize he may have been wrong all these years.
I thought it was cooperation in the hunt and the eating of meat that contributed to the growth in brain size. Before you can fight, you need to eat. Social organization follows and you need socialization to wage war.
Note, many of the diseases related to a the typical poor American diet tend to show up in older people - coronary heart disease, hypertension, loss of teeth, osteoporosis, etc. Diseases due to malnutrtion tend to strike the yougest members of a population. Malnutrition is a leading cause of death in the third world. Diet and the availability of food has been an important factor in the development of modern human history (since the time of the first pasoralists).
Modern medicine and the availability of a steady food supply has lengthened the human life span. I am making no judgement whether that is a good or bad thing. To the extent that we can adapt to the less healthy parts of our diet through our prime reproductive years, the selection process is working properly.
Then dogs should have brains as big as ours. It was the first murder, the first human with a temper, the first human who decided to rob and rape, that set the ball rolling of our advanced genetics.
Then, no question, I am an individually-wrapped, itty-bitty Snickers Bar. (Happens this time every year.)
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