The article below will eventually appear in the SF-LiFE newsletter. It
was inspired by two things:
1. An article from "Tropical Fruit News" magazine, that discussed how
the evolutionary design of fruit gives us insight as to who the optimal
fruit seed dispersal agents are, i.e. those animals the fruit "wants"
to be eaten by, and
2. Seeing various fruitarian extremists repeating the simplistic party
line, that "(all) fruit wants to be eaten by humans - by you".
Note that this topic was discussed previously on raw-food.
I hope you enjoy the article. Please note the copyright restrictions on
cross-posting, and the disclaimer re: the fact that it is a non-technical
article.
Tom Billings
-------------------------------------------------------------------------
DOES FRUIT "WANT" YOU TO EAT IT?
Comments Inspired by the Article, "Berry Time" (by Steve Howe)
Comments by Tom Billings
Copyright 1998 by Thomas E. Billings; all rights reserved. Contact author
for permission to crosspost on any other e-mail list, bulletin board, or
website, or republish in any way.
Disclaimer: This is a non-technical article, designed to introduce
the concepts and issues to the reader. As such, it has few references/
citations in it. A science-based article on the subject, replete with
many references and citations to the scientific literature, is under active
consideration as a future project. In the interim, inquisitive readers
are encouraged to investigate the appropriate scientific literature
for articles on the topics discussed below.
Let me begin by complimenting Steve Howe on an excellent article, "Berry Time",
originally published in "Tropical Fruit News Magazine", September 1998,
vol. 32, no. 9, pp. 10, 13. Said article includes a brief and readily
understandable discussion of fruit structure, as it relates to the optimal seed
dispersal agents, i.e., which animals "should" eat the fruit. We are
reprinting this interesting article to give members insight into the complex -
and wonderful - reality that is nature.
1.0 Introduction - Dubious Fruitarian Claims About Fruit
Two important claims central to fruitarian idealism are as follows.
(1) Fruit "wants" to be eaten - by you, or some other human.
(2) Because of (1), there are no toxins in fruit.
Not too surprisingly, the above claims commonly made by fruitarian diet
advocates, are inaccurate at best, and flat-out wrong some of the time.
2.0 Fruit "Wants" to Be Eaten -
But Not Necessarily By Humans
It should be understood from that start that the question, "does fruit want
to be eaten?", is figurative or rhetorical. Obviously, a straight answer to
the question is that fruits do not have brains, they cannot think or "want", so
the logical answer is that the question is irrelevant. Instead, the question
"does fruit want you to eat it?", will be interpreted as: "are you (or
humans in general), an appropriate (or optimal) seed dispersal agent for
a (specified) fruit?".
Another point that should be understood is that the term fruit has the
common definition here, i.e., the reproductive parts of a plant that reproduces
by seed, and which includes a juicy pulp. The botanical definition of
fruit is more general, and includes all seeds (e.g., nuts, grains). As the
fruitarian diet usually centers on juicy fruits rather than seeds, this
discussion uses the common definition of fruit.
The method by which fruit reproduces, hence survives in the evolutionary
sense, is by seed dispersal agent(s) - animals - eating the fruits and
depositing the fruit seeds elsewhere, where the seeds will hopefully
sprout and grow into a new plant. The most common seed dispersal agents
are birds or mammals, however insects and even fish, may serve as seed
dispersal agents, for certain fruits.
Thus, in a certain sense, the fruit tree "wants" its fruits to be eaten to
achieve seed dispersal and reproduction. However, the tree also obviously
"wants" its seeds to be dispersed by the appropriate or optimal seed dispersal
agent. Further, the fruit tree "wants" to prevent or limit, the consumption
of its fruits by undesirable (inefficient) seed dispersal agents, or - even
worse - seed predators, i.e. animals that devour and destroy the seeds. The
article by Steve Howe discusses how blackberries appear to have evolved for
consumption and dispersal by birds, but not by mammals.
Plants employ a wide variety of strategies in making their fruits
attractive to optimal/efficient seed dispersal agents, and unattractive to
undesirable (from the plant's goal of survival) seed dispersal agents or
seed predators. In the case of blackberries, sharp thorns and a growth pattern
that favors dense thickets, discourages berry consumption by mammals. Note that
thorns discourage or reduce blackberry consumption by mammals, but
do not prevent it completely. In nature, adaptations occur in response
to multiple selective evolutionary pressures operating simultaneously
over a long time period, and the observed result is actually a compromise
solution. One way to precisely target fruit to select seed dispersal agents,
is via the use of selective toxins. However, it appears that the blackberry
has evolved structural features as its primary method to discourage berry
consumption by mammals.
3.0 Fruit Does Contain Toxins -
The Functions of Toxins in Fruits
Virtually every part of every plant contains chemicals that, in isolation
and in high doses, are toxic. In reality, fruits usually contain (some)
toxins for a number of reasons, as follows.
1. To protect from insect attack, before the fruit ripens.
The use of chemicals - toxins - to protect from insect attack, is standard
practice among plants. Some plants use other defenses as well, but chemicals
(toxins) are the first line of defense for most plants. The levels of
natural pesticides present will presumably be highest in immature fruit, and
lowest in mature, ripe fruit.
2. To differentiate which species eats the fruit; i.e. to promote fruit
consumption by the animal(s) that are optimal seed dispersal agents,
and to discourage consumption by other animals.
As the article by Steve Howe so nicely describes, the structure of a fruit
may suggest which seed dispersal agents (fruit consumers) are optimal
for a given fruit. Another approach that has evolved is, once again,
chemical. If a plant "wants" its seeds dispersed by, say, birds, rather
than mammals, one way to promote such an end, is to include chemicals -
toxins - in the fruit that are harmless to birds, but which are irritating
or taste bad to mammals. Hot peppers may be an example of such a strategy,
although many omnivorous humans have learned to enjoy hot peppers anyway!
3. To control how much of the fruit is eaten by the optimal seed dispersal
agent, at each sitting.
Once again, chemicals - toxins - may be used to regulate how much fruit is eaten
at a given sitting by a seed dispersal agent (a hungry animal eating the fruit).
The reason to regulate it is that survival - reproduction of the plant - is
probably not maximized if large amounts of fruit are eaten at each sitting,
as then there are fewer piles of dung deposited (dung that contains fruit
seeds). The more dung piles with fruit seeds in them, the greater the
chance of reproductive success - and evolutionary survival - of the fruit.
Note here that the amount of toxin in a fruit is, by necessity, a trade-off:
a compromise between limiting the amount consumed, versus allowing the
animal to consume enough fruit so that it will bother to expend the energy
required to harvest and eat the fruit (and thereby, ultimately disseminate
the fruit seeds). Once again, nature is a series of complex trade-offs and
compromises, rather than a set of simplistic principles (e.g., the simplistic
claims of fruitarian extremists).
4. Once the seed is deposited in a dung pile and sprouts, toxins may
serve as natural fungicides, and to protect the sprout until it is
able to produce its own defensive toxins.
Sprouting seeds are subject to attack by a number of fungi, particularly
a fungus known as "damping off". In addition, sprouts/seedlings may be
subject to insect attack (e.g., cutworms). The presence of toxins in
the seed, seed coat, or fruit pulp, may help to protect the seedling until
it is large enough to produce its own natural pesticides.
Thus we note that the claim that fruit has "no toxins" and hence is a
"perfect food" is simply another example of over-simplification and
excessive idealism by the promoters of fruitarian diets.
4.0 Raw-Diet Psychology Regarding Toxins in Food -
Pathological Fear?
In the raw diet community, one often encounters the following invalid logic:
a. Substance Z is toxic (usually not mentioned: in isolation and in very
large doses)
b. Food X contains substance Z (usually not mentioned: amount/dosage)
c. Conclusion: therefore, food X is "toxic".
The above logic is an example of the simplistic, black and white reasoning
that is common in the raw diet community. This type of invalid logic is
used by certain fruitarian extremists, who claim that fruit has no toxins,
but all other foods do. (Consequently, said extremists advocate a diet
that is nearly 100% fruit.) The result of such invalid logic, is
that the possibility of toxins in food becomes a phobia, and a (sometimes
life-controlling) pathological fear for some who follow raw diets. Needless
to say, pathological fear is not the basis for a healthy diet - it is,
however, the basis for an eating disorder.
There are many errors in the above bogus logic. A brief list is as follows.
* Virtually all foods contain substances that, in isolation and in large
quantities, are toxic. Even water, in huge doses, may be toxic; after all,
people have committed suicide by drinking water. Does it then follow that
virtually every food is "toxic"?
* A discussion of toxins in foods should include: data on amount of toxin in
the food, and in a typical meal including the food; said data must then be
evaluated in light of data on the bioavailability of the toxin, and the
amount of the toxin required for a harmful dose. That is, one must look
realistically at the food as a whole, and consider the possibility of harmful
effects from eating the food (in the case of most common foods, the risk
of harm is usually very low). The invalid logic described above - points
a,b,c - is much closer to fear-mongering than rational thinking.
* Humans have extensive detox systems - liver, kidneys, etc. - for good reasons.
Our detox systems help protect us from natural toxins - which are found
in all foods, whether raw or cooked, processed or unprocessed, vegetarian or
non-vegetarian. The paranoid, pathological fear of toxins (in food) that one
frequently finds in the raw diet community, is, quite frankly, very mentally
UNhealthy. The pathological fear (and hatred) of cooked foods promoted by
certain raw diet extremists, is far more dangerous to your health (in my
opinion and experience), than eating say, a simple diet that includes some
whole, cooked foods.
* Evidence of the significant power of detox systems: the following quote
from Huffman [1997] discusses how primates are well-adapted to consumption
of potentially hazardous plant compounds (pp. 171-172),
"Among primatologists a major focus of concern about plant secondary
compounds in the diet has been on how and why primates can cope with their
presence (Glander, 1975, 1982; Hladik, 1977a,b; Janzen, 1978;
McKey, 1978; Milton, 1979; Oates et al., 1977, 1980; Wrangham
and Waterman, 1981). An extreme case in point is the golden bamboo
lemur (Hapalemur aurensis) of Madagascar, which is noted to consume
over 12 times the lethal adult dose of cyanide in a day, without ill
affect (Glander et al., 1989). The cyanide comes from the tips of a
bamboo species, Cephalostachyum sp. (Graminaea), consumed as part
of the lemur's daily diet at certain times of the year (Glander et
al., 1989). In this case, the cyanide is thought to be detoxified
mostly in the liver (Westly, 1980)."
Note: for references cited above, see Huffman [1997].
4.0 Are Fruits that Evolved for Dissemination for Non-Human Animals,
a Suitable Food for Humans?
This question must be answered on an individual basis, i.e., per individual
fruit. Sweeping generalizations are inappropriate here. Some fruits are
toxic to humans but are consumed by birds, squirrels, or other animals.
Some fruits appear to have evolved for dissemination by birds (e.g.
blackberries, raspberries), but are quite suitable (and delicious!) food
for humans.
5.0 Summary/Conclusions
The claim made by promoters of fruitarian diets, that fruit "wants you to
eat it", is an over-simplification that is frequently based on wishful
thinking and idealism, rather than reality. For example, some fruits have
evolved to be eaten by birds, rather than mammals/humans, as the article
by Steve Howe discusses. Note, however, that a fruit that has evolved to be
disseminated by non-human animals may be a suitable food for humans; each
fruit must be considered individually. Further, the claim that fruit
is the only food free of "toxins", is yet another example of idealism and
wishful thinking. Readers should be cautious of such claims - idealism and
wishful thinking, though attractive in many ways, can be harmful to your
health if they lead you to a diet that is not appropriate for you.
References.
Huffman, M H; 1997; "Current evidence for self-medication in primates: a
multidisciplinary perspective"; Yearbook of Physical Anthropology; vol.
40, pp. 171-200.
*************************************************************************
For articles on fruitarianism and raw diets, visit the new Internet
web site, "Beyond Vegetarianism", URL: < http://www.beyondveg.com >.
Free Internet web site access is available at many public libraries.
*************************************************************************
|
