• The reference to an ancient frugivorous ancestor is so vague that it is meaningless. True, there were ancient frugivorous primates. However, the reference mixes up the diverse categories of primates, hominoids, and humans such that no meaningful statements can be made. Another problem here is that--as has been discussed earlier--the type of fruits eaten by earlier frugivorous apes included tougher and more fibrous fruits considerably different in character than the highly bred and far sweeter varieties developed for commercial production in modern times.

• Humans have been eating meat since the dawn of the Homo genus. Humans appeared with the advent of a brand-new genus (Homo) ~2.5 million years ago. Humans evolved on the savanna-- a very different environment from the forest home of the great apes. From the very inception of our genus, humans have been eating animal foods. There is overwhelming scientific evidence to support this point. (Some of the evidence is discussed in this and the preceding section; also see Part 1 of the Paleolithic Diet vs. Vegetarianism interview series, available on this site, for additional information and citations.) The diet of some vague prehistoric frugivore that may or may not be an ancestor is irrelevant in light of the status of humans as a new genus with a different diet (i.e., eating more animal foods) and evolving in a different environmental niche.

  In contrast to the extensive fossil record evidence of meat in the evolutionary diet, there is virtually no credible scientific evidence of a strict fruitarian or veg*n diet by our prehistoric human (and australopithecine) ancestors.

• Egocentric claims. Unscientific, blatantly egocentric claims that eating foods other than fruit is "maladaptive," or "in error." (These claims were discussed earlier in this paper, and are also reviewed in the article Selected Myths of Raw Foods.)

• Denial of evolutionary adaptation. Fallacious claims that humans did not or could not adapt, via evolution, to a diet that included animal foods (fauna), despite ~2.5 million years of evolution on such diets. (The topic of physiological adaptation is discussed later herein.)

• Straw-man arguments based on SAD/SWD diets, i.e., citation of clinical research that shows conventional vegan diets (not fruitarian diets) are better than the standard Western diet. The logical fallacies of this approach (which use the evidence against the typical Western diet to create a "straw man" to stand in for all omnivorous diets) are discussed in a later section.

• Uninformed comparative anatomy. Claiming that comparative anatomy indicates we evolved to become fruitarians. This claim is addressed in the sections that follow.

• "Protein is toxic" claims. The presentation of ancillary crank science claims, i.e., that "protein is toxic," in the sense that any excess protein--any above a very low standard much lower than cited even in conventional vegan research--produces metabolic by-products that are poison and will harm you. This crank science theory is then used to "prove" that animal foods are unnatural because they allegedly contain excess protein. Such theories are based on amazing ignorance of the reality that the human body is very well equipped to dispose of the metabolic by-products of protein digestion. Note: See the article, "Is Protein Toxic?" on this site (not yet available), for a detailed discussion of some of the anti-protein crank science theories.

• Paranoia-based theories. Another factor in such crank theories is that they appear to be based on an intensely paranoid, pathological fear of any/all possible "toxins" from food, and hence such theories may actually (indirectly) promote obsession with unachievable ideals of total dietary purity, sometimes leading to eating disorders.

• "Fruit is like mother's milk" analogies. Claiming that human milk (a food whose calories are predominantly from fat) is "just like" sweet fruit--a food whose calories are predominantly from sugar. (Most people seem easily enough able to tell the difference between fat and sugar, though apparently certain fruitarian extremists have major, inexplicable difficulties in perceiving this distinction.) This claim has been blown up into a major bulwark used by some to promote fruitarianism, and is another prime example of bogus crank science. (See the article Fruit is Not Like Mother's Milk for details.)

• Despite the fossil record evidence of physical/anatomical evolution in the last ~2.5 million years, physiological evolution--specifically of the digestive system--did not and in fact could not have occurred.

• Because of the preceding, humans are still adapted to a fruitarian diet because of the (mystical) alleged ancient frugivorous primate ancestor, discussed in a previous section.

• Similarly, those who make the above two claims must also claim that meat-eating is "maladaptive," and that somehow the human genus survived and evolved (except for the digestive system, of course) over ~2.5 million years of evolution on a "maladaptive" diet! (Does common sense tell you anything about such far-fetched claims?)

Analysis of the Fruitarian Claims

CLAIM: Morphological evolution is "easy," physiological evolution is nearly impossible. The basic claim is that mutations that impact morphology--skin color, bone size, etc., have a minor impact on the organism, while mutations that produce physiological changes occur under what seem to be more complicated interactions, hence are less likely to succeed or enhance survival.

REPLY: The claim is not only misleading and an implicit oversimplification, but a good example of the way such claims are often hastily grasped at without thinking carefully through them first. As changes within the human body occur in a system in which both morphology and physiology are unified, physical changes often cannot be easily divided into two distinct categories, morphological and physiological. In reality, morphology and physiology are closely interrelated. Such morphological parameters as body size and shape are in fact regulated by hormones, which are part of your physiology.

Hormone regulation of morphology/physiology. For example, bone growth and size of the bones/body are regulated by pituitary growth hormones and sex hormones. In turn, the growth hormones are themselves regulated by releasing hormones produced by the hypothalamus, which is in the brain. (See Tortora and Anagostakos [1981], and Tanner [1992] for relevant discussion of hormones.) This implies that any significant evolutionary change in morphology requires an associated simultaneous change in physiology, i.e., the relevant hormones must change as well.

Thus we observe that a binary or "black-and-white" classification of changes as either morphological or physiological does not match well with reality. Once again, fruitarian extremists are engaging in the binary thinking and oversimplification that is characteristic of such dietary dogma.

As a postscript to this topic, the remark of Tanner [1992b] is relevant:

Differential growth rates are very often the mechanism of morphological evolution in primates...

REPLY: The above is an unsupported rationalization. Consider that the human brain is far more complex than the digestive system, and that the physiology of the entire body is regulated via the autonomic nervous system, which is controlled by the brain. More precisely, some of the control of the autonomic nervous system rests in the cortex [Tortora and Anagostakos 1981, p. 374], and the cortex is the part of the human brain that is larger and has further evolved vis-a-vis the great apes [Stephan 1972]. Thus we observe that the "master controller" of the human physiology is the brain, with the cortex playing a key role.

Then we note that the human brain has in fact evolved (quite considerably) during the period, i.e., the "master controller" of the human physiology has evolved significantly in the last ~2.5 million years since the human genus first appeared. Thus, the bizarre claim that the physiology of the human digestive system could not have evolved during the period is easily seen as the ludicrous fantasy that it is.

Mutations that deviate from the norm often interfere with biochemical processes and are rigorously removed by selection. Much of the body is made up of the building blocks of cells, which must fit accurately with one another... Any mutation that changes the shape of such molecules will almost always be at a disadvantage as it reduces their ability to interact with each other or with their substrate. Stabilising selection of this kind can be a very conservative force.

Stabilising selection is a powerful agent that leads to genetic homogeneity. To explain how genetic variation is maintained in the face of such widespread censorship by natural selection is one of the main problems of population genetics.

REPLY: There is also no convincing teleonomy proof that humans have adapted to a strict fruitarian diet! The appeal to teleonomy is, thus, a red herring (i.e., a diversion) and nothing more.

Teleonomy, the scientific study of adaptations, is sometimes used as a defense of fruitarian evolution. Basically, the teleonomy proof argument is nothing more than a diversion--the fruitarian extremist demands what is implied to be definitive "proof," a teleonomy study or analysis, that "proves" humans have adapted to meat in the diet. Such claims are simply diversions, however, because those who make them do not have teleonomy "proof" that humans are adapted to a fruitarian diet either. In effect, the claim is used (if unconsciously) as a smokescreen to divert attention from the total lack of legitimate scientific evidence to support the fruitarian evolution theories.

A few comments on teleonomy are appropriate here. Thornhill [1996, p. 107] provides an introduction to teleonomy, and he defines teleonomy as:

...[T]he study of the purposeful or functional design of living systems and the directional pressures that have designed adaptations during long-term evolution.

Criticisms and limitations of teleonomy. Teleonomy is also known as the adaptationist program, and a well-known critique of the subject is provided by Gould and Lewontin [1994]. An interesting paper on the many statistical challenges faced in doing teleonomy studies is Pagel and Harvey [1988]. As will be discussed later in this paper, humans are unique in nature by virtue of certain important features: high intelligence, language, etc. This uniqueness, coupled with the serious statistical problems inherent in cross-species comparisons, presents major statistical and analytical challenges to those who wish to unequivocally "prove" adaptation in humans (vis-a-vis other species) via teleonomy studies. As such, perhaps the best way to view teleonomy is as one analytical tool (out of many tools) available to the researcher, rather than the "best tool" or "only (valid) tool," which is what fruitarian extremists appear to imply in their use of teleonomy as a last-ditch defense of their crank science theories.

REPLY: Evolution does not move backwards or forwards. Evolution occurs as the result of changes over time, the result of selective pressures in the environment (which can include behavior, especially for humans, per discussion in a previous section). The use of the word "backwards" shows the emotional nature of the fruitarian evolution claims. The idea that evolving from a vegetarian diet to an omnivorous (or faunivorous) diet is "backwards" is purely a subjective bias. Nature simply IS; our subjective opinions of the process are irrelevant.

REPLY: The answer to this question will be apparent in the later sections of this paper. Though a short answer could be given here, it would remove the element of surprise from some of the following sections. This question is answered and addressed later with relevant details and context.

• That the human digestive system is an evolutionary throwback to some mystical frugivorous ancestor, and,

• That the human body, including the brain--but not the digestive system!--has evolved over the last ~2.5 million years. In other words: Those who cling to false fruitarian evolution theories are claiming that evolution works, but not for the digestive system; the brain can evolve but the stomach cannot. Such bizarre assertions place the fruitarian evolution theory squarely in the realm of science fantasy rather than fact.

Return to beginning of article

SEE REFERENCE LIST

SEE TABLE OF CONTENTS FOR:
PART 1 PART 2 PART 3 PART 4 PART 5 PART 6 PART 7 PART 8 PART 9

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GO TO PART 1 - Brief Overview: What is the Relevance of Comparative Anatomical and Physiological "Proofs"?

GO TO PART 2 - Looking at Ape Diets: Myths, Realities, and Rationalizations

GO TO PART 3 - The Fossil-Record Evidence about Human Diet

GO TO PART 4 - Intelligence, Evolution of the Human Brain, and Diet

GO TO PART 5 - Limitations on Comparative Dietary Proofs

GO TO PART 6 - What Comparative Anatomy Does and Doesn't Tell Us about Human Diet

GO TO PART 7 - Insights about Human Nutrition & Digestion from Comparative Physiology

GO TO PART 8 - Further Issues in the Debate over Omnivorous vs. Vegetarian Diets

GO TO PART 9 - Conclusions: The End, or The Beginning of a New Approach to Your Diet?

Back to Research-Based Appraisals of Alternative Diet Lore