|Evolution in the News - December 2002|
|by Do-While Jones|
William R. Leonard’s article “Food for Thought” says “Dietary change was a driving force in human evolution” 1. What does he mean by that? Is there any evidence to support his claim?
Perhaps Leonard didn’t really say, “Dietary change was a driving force in human evolution.” I’ve published more than 50 articles in major electrical engineering or software development magazines, and it has been my experience that editors rarely change anything I write in the body of the article, but they almost always change the title. It could very well be that one of the editors at Scientific American added that provocative subtitle simply to entice readers to buy the magazine. The subtitle seems inconsistent with the style and substance of Leonard’s article.
Regardless of the source, that subtitle certainly implies that diet somehow changes the DNA in the reproductive cells, so that the offspring are better suited for survival. At least, that’s what people just flipping through the magazine are most likely to think.
Is that what evolutionists really believe? John D thinks evolutionists believe that mutations cause the genetic changes, and the availability of food merely acts as a filter which preserves beneficial mutations.
Who is right? How does Leonard understand that creatures adapt to their environments?
It is difficult to say because the article is ambiguous and filled with double-talk. We haven’t heard anyone talk so much while saying so little since the elections were over last month. Leonard's article is a political masterpiece. Even after very close scrutiny, we don’t really know what he believes. In the entire 9-page article, the closest Leonard came to giving an explanation was,
After the initial spurt in brain growth, diet and brain expansion probably interacted synergistically: bigger brains produced more complex social behavior, which led to further shifts in foraging tactics and improved diet, which in turn fostered additional brain evolution. 2
Even this statement isn’t entirely clear. It could mean one of three things.
The first possibility (which would probably be assumed by the casual reader) is that Leonard believes increased mental activity required by “complex social behavior” caused increased mental development, which was inherited. This increased mental development required an improved diet, which meant man needed even more complex social behavior to develop improved foraging tactics, which exercised his brain even more, causing increased mental development which was inherited. This brain required an even richer diet, which required more thought, ad infinitum.
The fallacy with this line of reasoning is that intelligence has to be inherited for evolution to occur. One of the few things that Darwin got right is that inheritance is the key to evolution. If an individual acquires a new trait, but that new trait isn’t inherited by its children, then the evolutionary advancement disappears as soon as the individual dies. There is no lasting change in the population if the new trait isn’t inherited.
It isn’t clear to us how Leonard might think intelligence is inherited. Physical exercise produces stronger muscles, but children don’t inherit the stronger muscles from their parents. In the same way, mental exercise probably does promote brain development, but that advanced development would not be inherited.
He clearly believes that an improved diet produces a bigger, smarter brain, and that the improved brain is inherited somehow. But he never really says how he thinks that happens. Since the idea that acquired characteristics are inherited is inconsistent with modern genetic knowledge, let’s give him the benefit of the doubt and presume that he doesn’t really believe this. If he doesn’t believe this, what does he believe?
The second possibility is that there are genes which affect the ability of the brain to function. Some combinations of genes are better than others when it comes to producing an intelligent brain. To put it bluntly, the evolutionary argument is that some people are genetically smarter than others. Natural selection will favor those combinations of genes which produce smarter brains. The smart combinations of genes will become dominant in the population, resulting in a population with a higher IQ.
Since those smarter brains require more energy, diet figures into the equation because people who are too stupid to find food will starve before they reproduce. Only those people smart enough to find enough food to feed their bigger, smarter brains will survive.
There are two problems with this understanding. First, there are still a lot of stupid people in the world today. You see them in the cars that cut you off on the freeway, or pass you over a double-yellow line. Natural selection doesn’t seem to be powerful enough to eliminate stupidity, even with the help of potentially lethal motor vehicles.
The second problem with the second possibility is that it involves the combination of existing genes. The theory of evolution is supposed to explain where genes came from. Any explanation that requires the genes to be there in the first place, is an unsatisfactory explanation of evolutionary origin.
So, this leads to the third possibility. It is alleged that random changes to the DNA in egg or sperm cells created genes which, in some combinations, produced bigger, more complex brains which required more energy to run. These energy-expensive brains were smart enough to figure out how to find food. These random changes were inherited. Then, more random changes produced even bigger, even more complex brains, which required even more energy.
There are four problems with the third possibility. First, as we have previously seen, natural selection just doesn’t seem to be powerful enough to eliminate stupidity. We don’t need to dwell on this.
The second problem is that it requires a series of independent, fortunate accidents. In other words, each step in intelligence is caused by a lucky mutation which is not related to diet. Leonard doesn’t suggest that certain foods cause genetic mutations which improve brain function. So, diet isn’t a cause of increased intelligence. Inadequate diet merely causes natural selection to eliminate individuals (and groups of individuals) less able to survive. The rich diet doesn’t cause new intelligence to arise.
The third problem is that the mutant baby with the bigger brain, which requires more energy, is sucking the breast of a mother with a little brain. The baby is likely to die from malnutrition before it is smart enough to find food for itself, unless the ability to give more milk evolves at the same time. A positive correlation of bigger brains with bigger breasts is required. (Let’s not open that can of worms! )
The fourth problem with the third possibility is that one has to believe that genetically useful information can be produced from random changes. There is no scientific evidence showing that random changes can increase genetic information.
None of the three possible explanations for how diet is related to brain evolution is scientifically viable. That’s why evolutionists are forced to make vacuous, ambiguous statements which make it appear that there is an obvious explanation that you are too stupid to understand. But when you try to pin them down, you find out how slippery they are.
What does Scientific American really want us to believe about brain evolution? Let’s really try to figure it out. In a sidebar titled “Overview/Diet and Human Evolution” there are two bullets. The first bullet says,
The characteristics that most distinguish humans from other primates are largely the results of natural selection acting to improve the quality of the human diet and the efficiency with which our ancestors obtained food. 3
Let’s chew on that a little bit. Somehow diet and natural selection are involved in human evolution, but how? It doesn’t say. There isn’t a clue. They just make the groundless assertion and expect readers to accept it without question.
The second bullet in that same sidebar says,
Yet studies of traditionally living populations show that modern humans are able to meet their nutritional needs using a wide variety of dietary strategies. 4
In other words, diet and the methods of obtaining food don’t seem to matter. There are lots of different ways to obtain sufficient food, so there really isn’t any reason for natural selection to select one over another.
The two bullets in the overview sidebar contradict each other. Why did the editors include it? Maybe they were trying to make readers think that Leonard has found the answer to a paradox, so that they will buy the magazine.
Regardless of their motives, the fact remains that there are many different cultures in the world today, eating traditional diets which differ greatly from each other, and it doesn’t seem to affect their average intelligence at all. Since we don’t see diet working to improve intelligence today, it is unreasonable to think that it affected intelligence in the past.
The overview (which may have been written by a Scientific American editor rather than Leonard) wasn’t any help, so let's try Leonard’s introduction to the article itself.
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. 5
What does this tell us? First, it tells us that anthropologists and biologists have been guessing for years. The guess gaining most popularity in recent years is that it has something to do with diet.
The reader might reasonably expect that the body of the article would contain the “growing body of evidence” which explains how diet affects evolution. Instead, the obvious is stated, and the reader has to assume the implied arguments. For example,
Contemporary human populations the world over have diets richer in calories and nutrients than those of our cousins, the great apes. 6
The implication is that if you eat lots of calories, and take mega-multivitamins, you will get smarter, and your children will inherit your intelligence. But we know that isn’t true.
He doesn’t come right out and say that eating high-calorie food will make you smarter. But if he doesn’t think there is a relationship, why did he compare the diets of humans and apes? The average reader will probably assume that there is scientific evidence that shows a relationship between calories and intelligence. If an alert reader challenges this assertion, Leonard can weasel out by arguing that he never said there was a relationship. Let’s not pussy-foot around. Is there a relationship between diet and intelligence, or not?
The long-running debate among evolutionists is which evolved first--upright posture or larger brains. Leonard argues that upright posture evolved first.
… [C]ost-effective walking saves many calories in maintenance energy needs--calories that can instead go toward reproduction. 7
Upright walking certainly is more efficient than walking on all fours (at least for people). Try walking around the house on all fours and see how quickly you get tired. So, you will burn up less calories walking on two legs. But the idea that unused calories will “go toward reproduction” is pure speculation. It is not backed up by studies that show beer-guzzling couch potatoes have more sexual energy than other men who eat less and exercise more.
But right after saying that the unused calories could be used for sex, he says that isn’t how we used them. We needed all those extra calories to keep our brains running.
We therefore use a much greater share of our daily energy budget to feed our voracious brains. In fact, at rest brain metabolism accounts for a whopping 20 to 25 percent of an adult human's energy needs--far more than the 8 to 10 percent observed in nonhuman primates, and more still than the 3 to 5 percent allotted to the brain by other mammals. 8
OK. Our brains need lots of energy. That is scientific. Scientists can measure energy use. But a measurement of energy use doesn’t explain the history of brain development.
How did such an energetically costly brain evolve? One theory, developed by Dean Falk of Florida State University, holds that bipedalism enabled hominids to cool their cranial blood, thereby freeing the heat-sensitive brain of the temperature constraints that had kept its size in check. I suspect that, as with bipedalism, a number of selective factors were probably at work. But brain expansion almost certainly could not have occurred until hominids adopted a diet sufficiently rich in calories and nutrients to meet the associated costs. 9
In other words, they don’t know. They keep telling stories until they find one that most people will believe. That isn’t science.
Leonard “suspects” that several (unspecified) factors were involved. He thinks brains were eagerly, actively trying to evolve. The brains just could not do it until man learned to walk upright, so he would have enough energy to walk farther, and gather more and better food. Once the diet was improved, it allowed the brain to evolve.
Then Leonard begins a line of reasoning that is bound to offend vegetarians.
Animal foods are far denser in calories and nutrients than most plant foods. 10
In other words, vegetarians can’t get enough calories and nutrients to think as well as carnivores. Is there any scientific study linking intelligence to meat-eating? When doctors recommend a vegetarian diet, do they tell their patients, “If you switch to a vegetarian diet you will probably live longer, you will have less risk of heart disease, less risk of cancer, and be a lot dumber” ?
High calorie diets don’t make people smarter than chimps and stronger than gorillas. They just make us fat. Leonard knows that. In fact, he says,
In the industrial world … rates of childhood and adult obesity are rising because the energy-rich foods we crave--notably those packed with fat and sugar--have become widely available and relatively inexpensive. According to recent estimates, more than half of adult Americans are overweight or obese. … We are victims of our own evolutionary success, having developed a calorie-packed diet while minimizing the amount of maintenance energy expended on physical activity. 11
Why are our waistlines expanding now instead of our brains? What has changed? If good food used to make us smarter, why does it now just make us fat, dumb, and happy? Isn’t there any selective advantage to being smarter any more? Is there a selective advantage to being fat?
We may not be able to definitively conclude what serious evolutionists really believe because they may not even know themselves. But articles like Leonard’s, with subtitles like “Dietary change was a driving force in human evolution”, make it appear to the casual reader that scientists believe that diet causes inheritable changes. We doubt you will be able to find a scientist who believes that, though.
It doesn’t really matter what “scientists believe”. It matters what you believe.
Do you believe, like Darwin, that diet, exercise, and environment cause inheritable changes? If so, why do you believe that? Hasn’t that notion been disproved by modern genetics to your satisfaction?
Do you believe that different combinations of genes cause different individuals of the same species to be slightly different? We hope so, because there is good experimental evidence of that, dating back from Gregor Mendel up to the most recent genetic engineering experiments. Dog breeders, horse breeders, pigeon breeders, and plant breeders have been using artificial selection to take advantage of that for years. Reproductive isolation and natural selection have caused some species to diversify into slightly different variations of species. But that doesn’t answer the question, “Where did those genes come from?”
Do you believe that accidental scrambling of the “letters” (or even “words”) in the DNA molecule can create genes for smarter brains? If so, why do you believe it? Can you cite any scientific evidence to support that idea? We think not because we have never seen any.
For the theory of evolution to be able to explain the appearance of new body parts, or new forms of life, it must be the case that random changes can create new, functioning genes which can be favored by natural selection. There is no scientific evidence to support this idea. That’s why there are so many articles like Leonard’s which imply a scientifically verified correlation ( like the correlation between diet and intelligence) when none exists.
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Leonard, Scientific American, December 2002, “Food for Thought” pages 106 - 115
2 ibid. page 112
3 ibid. page 109.
5 ibid. page 108.
7 ibid. page 109.
8 ibid. page 110.
9 ibid. page 111.
11 ibid. pages 114-115.