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Tropical forest biochemistry, the driving force in human evolution (cont.)
By Tony Wright

In effect eating a diet rich in fruit/flowers significantly alters your endocrine system. This creates a blanket effect, all aspects of growth development and physiology will be modified though any part of the physiology that is particularly steroid sensitive will exhibit the most significant response i.e. developmental windows, developing neural tissue, fertility cycles etc.

This almost certainly happened when proto-primates began to eat flowers and then fruit as well as leaves etc. The potential to extend the juvenile phase by inhibiting sex steroids and in turn allow a longer period of brain growth is perhaps the most obvious effect.

These effects have never been considered in an evolutionary context. Rather than trying to explain brain expansion from an adaptive perspective in regard to single traits it becomes possible to see the brain and other features as a fortuitous by product of a biochemically modified endocrine system.

(I have proposed one further step in regard to hominid/human evolution. Given sufficient variation in the effects of flavonoids on the developing neuroendocrine system it seems plausible that in some instances the modified endocrine system itself begins to add a layer of steroid inhibition. For example, elevating the activity of the pineal gland produces more melatonin and pinoline, both powerful steroid inhibitors. In such a scenario the scene is set for a classic runaway feedback loop, more steroid inhibition further expansion of the brain and modification of the endocrine system equals more blanket steroid inhibition etc. As these effects are not locked into the DNA in an adaptive sense they are potentially unstable, lose any part of the positive feedback loop i.e. the tropical forest flavonoids and it will stall. There is some evidence for such a scenario.)

There are undoubtedly a number of variables to consider

  • The genetic predisposition/sensitivity of any given primate lineage.
  • The variable % of fruit/flowers in a given dietary specialisation.
  • The variable outcome in any combination of above.

While these and other factors need to be considered the overall effect of these plant chemicals is not in doubt. Their power is sufficient that detrimental as well as beneficial effects may well have initially occurred. However it is entirely plausible that any primates that significantly specialised in fruit/flowers would exhibit the greatest effects.

The question that needs to be addressed now is how can our neuroendocrine system possibly function without a complex cocktail of powerful steroid modifying chemicals that were permanently present during 70 million years of evolution?

Aside from proposing that plant chemicals initiated and drove the structural/functional evolution of our brain I have also proposed that the loss of these chemicals left our uninhibited endocrine system unable to provide an appropriate hormonal environment for our brain to develop. Once our connection with the forest was lost our brain stopped expanding and now fails to develop it full function.

Due to archaic specialisation between the cerebral hemispheres I have proposed that the effects of the loss of these chemicals is lateralised one side being more affected than the other. Cerebral dominance and handedness etc are symptoms of this condition.

Significant evidence is emerging to support this scenario, Professor Alan Snyder (Director, Centre for the Mind, Australia) Dr Darold Treffert (University of Wisconsin Medical School) and Professor Vilayanur Ramachandran amongst others have increasingly highlighted a somewhat perplexing scenario. The dominant side of our brain is considerably less functional than the non-dominant side, the emerging data is still considered within the framework of adaptive selection i.e. there must be an evolutionary reason for the phenomena.

Shamanic techniques (i.e. sleep deprivation) and ethnobotanical use of plant chemicals were an attempt to address the emerging condition. For example the widespread use of plant DMT combined with MAO inhibitors was simply a crude attempt to ameliorate a progressive reduction in the production of neural DMT and pinoline in the brain. These and other deficiencies emerged as the human neuro-endocrine system struggled to function normally once the plant hormones were lost.


Flavonoids are extremely potent endocrine modulators.

They were an integral part of our endocrine system for tens of millions of years, their impact on our general health is only just beginning to be researched. Their effects on growth and development in an evolutionary perspective have not been considered.

  • Flavonoids powerfully inhibit the activity of steroids
  • Flavonoids powerfully inhibit the conversion of steroids (androgens to estrogens)
  • Flavonoids inhibit monoamine oxidase increasing pineal production of melatonin
  • Melatonin powerfully inhibits the activity of steroids.

Steroids are central in all aspects of development growth and function. Neural development in the uterus is particularly sensitive to steroid activity as are steroid governed developmental windows i.e. puberty.

An increasingly specialised fruit diet rich in flavonoids would it seems explain many of the mysteries surrounding human evolution. The gross nutritional aspects are of some relevance i.e. larger fuel hungry brain requiring an ever-greater quantity of simple sugars, however it is the hormonal effects that have thus far been ignored.

Once equipped with an increasingly large brain and the intelligence it conveys it is feasible to survive in a range of hostile habitats. No doubt repeated waves of forest migrants did just that and survived and adapted as distinct species on the savannah or in temperate climates. The orthodox assumption is that the expansion of the brain must have been driven by selective adaptation in relatively hostile or challenging environments. Is there any evidence that the brain continued to expand in these environments or was it the relatively benign tropical forest and its complex hormone modifying biochemistry that played an essential part in the brain expansion formula?

Selected References

Savant for a day by Lawrence Osborne, New York Times Magazine, June 22, 2003

Savant Syndrome: An Extraordinary Condition A Synopsis: Past, Present, Future. Darold A. Treffert, MD

The Evolutionary Biology of Self-Deception, Laughter, Dreaming and Depression: Some Clues from Anosognosia. V. S. Ramachandran Medical Hypotheses (1996) 47, 347-362

Weird behaviour, creativity linked, by Melanie Moran/Vanderbilt University, Sept. 6, 2005

The Effects of Plant Flavonoids on Mammalian Cells: Implications for Inflammation, Heart Disease,and Cancer. Elliott Middleton, Jr.,Chithan Kandaswami, and Theoharis C. Theoharides PHARMACOLOGICAL REVIEWS Vol. 52, No. 4. 2000

Nutritional Characteristics of Wild Primate Foods: Do the Diets of Our Closest Living Relatives Have Lessons For Us? Katherine Milton, PHD Nutrition Vol. 15, No. 6 1999

Infant feeding with soy formula milk: effects on the testis and on blood testosterone levels in marmoset monkeys during the period of neonatal testicular activity. Richard M. Sharpe, Bronwen Martin, Keith Morris, Irene Greig, Chris McKinnell, Alan S. McNeilly and Marion Walker, Human Reproduction, Vol. 17, No. 7, 1692-1703, July 2002

Memories and Visions of Paradise, Heinberg, Richard, Quest Books, 1995

Vilayanur Ramachandran Centre for Brain and Cognition

Alan Snyder

Darold Treffert

© 2006 Tony Wright
Director, Experimental Consciousness Research

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