I'm writing a paper for school and I'm trying to build a case for a fruit-based diet being our natural fare. I'm well aware of the strong arguments supporting this case, but I'd like to approach it from an evolutionary standpoint if I can. Please don't reply with the other supporting arguments - thanks.
Specifically, I would like to address these two issues (if possible):
At what point in human evolution was a fruit-based diet discontinued? Has there been sufficient time since that point for our species to adapt to an omnivorous diet?
Read this book. It will answer all your questions and more.
I've been studying human dietary evolution for the past few months as I work on my new book, "Raw Food Weight Loss and Vitality," which has an extensive section on how we've evolved to thrive on a diet of fruit and tender leafy greens.
It's very well established that we are descended from fruit-eating apes. You may want to look into some of the papers of Katherine Milton, who has written extensively about this.
The relevant part of dietary history starts about 70 million years ago when one particular lineage of primates -something like a bug-eating tree shrew - crawled up into the rich foliage of the fruit trees that were just beginning to spread across the globe at that time and began to feast. Apparently these creatures liked what they found, and they stuck with it.
We evolved into greater apes over the course of millions of years. Exactly when we had adapted enough of our current traits to be considered human is debatable.
"Ardi," a human ancestor that lived 4.4 million years ago already had a number of distinctive human-like features, including the smaller jaw and canines that mark a distinct delineation between the apes that can before and us. Our ability to chew fiberous vegetation was declining, along with our gut volume, meaning we had to start embracing higher calorie foods.
Most argue this was cooked starches or meat, but it's also entirely possible that these early humans were learning to embrace higher calorie fruits and tender leafy greens.
Perhaps driven by natural disasters, roughly 200,000 years ago (others give dates within 50,000 years of this time in either direction) humanity left the equatorial forests of Africa for the rest of the world, eventually interbreeding with, killing, or outlasting all the previous hominid lines.
At this point, with the exception of hunter gatherer tribes that lived near the equator, fruit ceased to be the major caloric staple of our diet, but it has always played an important part in most regions. Starchy tubers, many types of vegetables, nuts, seeds, and fruit were the mainstays, but meat also played a part in most diets.
There is no evidence for the consumption of cooked food before 250,000 years ago.
Around 10,000 years ago "civilization" started. Although there had been limited farming beforehand as a supplement to gathered food, we started farming for most of our calories. We lost the varied, nutrient-rich diets we'd been eating, instead subsisting on a small number of nutrient-poor grain crops and vegetables.
Within a few generations these farmers were much smaller and more disease prone than their fathers and grandfathers who'd hunted and gathered.
That's from memory and my citations are buried in the draft of my book, but anyone looking for references will see them listed when the book comes out.
I hope that helps
This stuff is fascinating. I'm aware that it's very well established that our distant ancestors ate fruit-based diets. What I was looking for is well-established evidence of the splitting point when our lineage stopped eating frugivorously.
Andrew, it sounds like "Ardi" could be a good potential candidate to mark this divergence. Your project sounds really awesome BTW.
So can a species evolve from being frugivorous to being omnivorous in 4.5 million years? I'm guessing not. But it would be cool to hear an anthropologist weigh in. And of course NO species is ever evolved to thrive on cooked food.
So can a species evolve from being frugivorous to being omnivorous in 4.5 million years? I'm guessing not.
I think the argument could be made that we haven't actually evolved to being omnivorous; we've just convinced ourselves that we are, despite evidence to the contrary. I think it could also be argued that human beings have not been healthy during the course of our omnivorous diet (low life expectancy, a host of maladies, etc. have always been a part of our experience). The latter may support the former.
But it would be cool to hear an anthropologist weigh in.
I would suggest locating a few biological antrhopologists and/or primatologists and asking them questions about how exactly they determine what the past diets of the hominid species are? It may take an effort to sift through assumptions in order to arrive at the truth (if it is really known). I'm genuinely curious how the examination of a handful of skeletons can lead to sure knowledge of their diets.
And of course NO species is ever evolved to thrive on cooked food.
I'd say no species on our present earth is evolved to thrive on cooked food, but overall it's plausible that a species could evolve this way if given enough time to do so (not that this would be ideal). Evolution likely includes many possibilities as yet unseen.
The tricky thing with evolution is that if we completely divorce it from the idea of 'spontaneous species creation' then it becomes difficult to use the word 'natural' as an overall and enduring quality of any given species. What is natural at one point in time is natural because that species has evolved to that state. What was natural for that species prior to that may not be the same, simply because evolution has occurred, and the same goes for what will be natural for that species in the distant future. To use the term natural in the sense of an ever-enduring quality or state of a species is somewhat contrary to the theory of evolution. So, imho, the term natural should always be used with the term 'currently'.
Because of this I tend to approach the argument of diet in terms of what is currently optimal for human beings. We are at a state of evolution in which (it appears to us that) fruit is our optimal food source. Proving that this was so in the past will be much more difficult than proving it is so now (which is difficult enough ;), simply because we have little to no factual data on our distant ancestors.
Perhaps the approach to take would be to examine how/why we are currently evolved to thrive on a fruit-based diet, and then examine the similarities between our current species and our ancestor species (to whatever degree that's possible).
Keep in mind that our current western version of the history of human civilization is but one theory, and though it is widely accepted it is by no means the only explanation of human progress and movements.
Good luck with your paper! :)
Here's some posts Dr. Gosia has written on the subject of frugivorous human/pre-human origins, good stuff, including references to scientific studies for your convenience:
[see feb 20 entry]
[see dec 18 entry]
It's also worth studying primate evolution.
You should also know that there is in general very limited evidence on early humans and our ancestors, so we can only speculate if/when our ancestors were eating a predominantly fruit-based diet. it's not as if you're gonna be able to 'prove' that humans were totally lfrv for this specific duration at a certain time in history, but I think there's no question that we are of frugivorous ancestry.
Just stumbled on these quotes. Haven't verified them yet, but you might like them.
From Charles Darwin:
"The grading of forms, organic functions, customs and diets showed in an evident way that the normal food of man is vegetable like the anthropoids and apes and that our canine teeth are less developed than theirs and that we are not destined to compete with wild beasts or carnivorous animals."In his book The Origin of Man he tells us:
"Although we know nothing for certain about the time or place that man shed the thick hair that covered him, with much probability of being right we could say that he must have lived in a warm country where conditions were favourable to the frugivorous way of life which, to judge from analogies, must have been the way man lived."
Look into euprimates and the Terminal Feeding hypothesis, which sets out the origin of grasping hands and feet, probably the most definitive primate feature evolutionarily, arose at the same time that fruiting trees evolved.
Also stable isotope analysis of tooth enamel is a widely looked at factor in determining the diets of early hominids. The distinguishing between C3 and C4 characterized isotopes in enamel has been looked at by a lot of studies.
In the field of biological anthropology there's alot of cultural rhetoric about high quality animal foods versus low quality plant foods. This muddles much of the work done on hominid dietary choice in relation to evolution, correlating larger relative brain sizes with the reliance on animal based foods. Also the fossil record is decent, but at the same time not really that great.
Focusing on cultural patterns of eating and some of the nutrition sciences that have shown the benefits of a plant based diet may add some weight to your argument.