Iodine as Human Catalyst

Iodine may have been the very catalyst that sparked 'The March of Human Progress'

We have already seen (go back to Iodine) that the thyroid gland has key roles in reproduction, early body and brain development, and also in response to stress. Each of these three activities can interact, and each is dependent on the input of iodine.

Dr. Susan Crockford has very recently published a book, Rhythms of Life, that may, at last, demonstrate a mechanism that can induce one species to change into another 

New species, it's been said, can arise: 

• By random, accidental, but major mutations in genes - many will be harmful, many will do nothing at all, but just occasionally, one will do, just about right. MYH16 might have been one - a gene that controlled the development of jaw muscles in apes suddenly shut down in the human line about 2.5Mya. That little accident just may have freed up the human skull - unencumbered by massive jaw muscles, the brain had room to expand. Just So.

• By slow, steady decimation of those whose particular individual suite of genes was out-competed by rivals, who won more females, or were eaten by less predators, attacked by less parasites, or, generally survived better to reproduce. Gradually, and almost imperceptibly, their descendants changed into something quite different. Sea gulls are such beasts. From somewhere in the middle, black-backed gulls have spread East and West around the Northern Hemisphere. Somewhere, the two outflying populations meet up, and are not even on speaking, let alone mating terms, so by definition they are new species. But no-one knows quite where the two species actually separate.

• By being suddenly isolated in a new environment, perhaps on an island, where natural selection would soon sort out the quick, with the better genes, from the dead, without. Sooner or later, the island descendants become so different from their ancestors that they can't or won't mate with their stay-at-home cousins, thus forming a new species. Darwin's finches did just this on the Galapagos Islands, and cichlid fish in African lakes evolved within the twinkling of a palaeontologist's eye into myriads of different species, some living in tiny specific biomes, and others specialising in biting out bits of either the left, or the right side of other fish. (Or at least, they had, until most of them were eaten, very recently indeed, by introduced Nile Perch  
  Darwin's Dreampond - Tijs Goldshmidt MIT Press 1996

Susan Crockford has come up with a much better idea: 

Heterochrony - induced by changes in thyroid rhythm phenotypes

(I don't even now how to pronounce the word; it's not discussed much in even the better class of saloon bars, but, essentially it means:):

• Different body parts can grow at different rates and at different times during pre- & post-natal development, and give individuals within a species slightly different body shapes, physiology and behaviour. That idea has been around for a long time, but Crockford is the first to propose a biological mechanism - thyroid hormone rhythms - that could channel, coordinate, and speed up the process. 

• Changes in resulting body shape and chemistry (phenotype) could change feeding, mating and a host of other behaviours, perhaps resulting in a small group getting together, liking each other, and branching out into an entirely new line from their ancestors. Very quickly indeed.

• Darwin demonstrated that species did indeed change and also suggested why, but he couldn’t say how.

• Gould and Eldredge proposed, a quarter of a century ago, the idea of 'Punctuated Evolution' - boring stasis, followed by quick action (much like war) - but couldn't say how

• And what controls these changes ? - the thyroid gland, of course (go back to the top of the page).

• And what else does the thyroid gland control ? - stress reaction.

Stress-tolerant individuals, and their siblings and cousins, who have similar thyroid hormone pulses, leading to shared phenotypical (body shape) changes, would adapt very much more easily to new conditions, and could form a founder group for a new species.

Not 'Nature Red in Tooth and Claw', that interpretation of Darwinian evolution promoted by Herbert Spencer (he coined 'Survival of the Fittest') so beloved by right-wingers lucky enough to have rich or powerful fathers, but just: 'Hey, cool man - ride with the wave'.

"Recent evidence that thyroid hormone release is distinctly pulsatile in nature and that thyroid hormone rhythms vary according to both intrinsic and extrinsic factors, suggests to me the distinct  possibility that shifts in timing and intensity of TH pulses (i.e. changing thyroid hormone  rhythms, or THRs) are the biological mechanism through which individual short-term  adaptation is achieved in vertebrates.

Many seemingly unrelated morphological, physiological  and behavioral traits are not controlled by individual variable genes that act and inherit independently but by the small suite of tightly linked genes that exert their effects indirectly through control of the thyroid rhythm phenotype of each individual.

Selection for any manifestation of a particular TR phenotype in an ancestral population selects all traits under thyroid control, resulting in rapid and well-coordinated changes in descendants"

Just how did she jump to this conclusion? It must be one of the most penetrating insights into the mechanics of evolution since Darwin invented the stuff.

Unlike Kekulé, who conceived the '6 carbon ring' idea, the foundation of organic chemistry, while sitting on the top deck of a London omnibus, or Kary Mullis, who thought of the polymerase chain reaction, used in DNA 'fingerprinting' while doing much the same in a Greyhound bus, Susan Crockford did it the hard way, like Edison, who famously said:

"Genius is one percent inspiration and 99 percent perspiration."

Which famous saying is now, in line with modern scientific practice: © 1993-2003 Microsoft Corporation. All rights reserved. 
Just because I looked up who said it in their pissant little encyclopaedia.

Like Darwin, Crockford first looked at dogs

She argues that: "domesticates do not always result from one continuous process initiated by humans". 

Instead, she suggests the process is very often comprised of two distinct parts, the first of which (protodomestication) is initiated by the animals themselves. 

"Furthermore, animals that have undergone protodomestication share certain morphological, physiological and behavioural similarities indicating that thyroid hormones (THs) played a pivotal role in the heterochronic changes that occurred.

This paradigm is based on the testable hypothesis that particular physiological phenotypes - variations in TH metabolism that occur naturally among individuals comprising a species - are the critical characteristics targeted by natural selection.

Thyroid hormones are intimately involved in the biological mechanism that allows individuals to adapt their body functions, in a coordinated fashion, to changing environmental conditions over the short term (daily or seasonally), so she proposes that they also allow groups of individuals (species) to adapt to environmental conditions that change over much longer evolutionary time scales".

Concise, precise, and above all, a testable hypothesis - that is, it can be proven or not - that doesn't apply widely in the non-physical sciences.

Domestic animals all share certain characteristics

Almost all domesticated animals share a set of certain characteristics, all brought about by adaptation to one new environment - living with humans.

All these characters are regulated by thyroid hormones.

·        overall body size reduction;

·        shortening of the facial bones of the skull, changes in dentition and smaller horns in cattle, sheep & goats;

·        lowered age of sexual maturity;

·        increased docility (lessened fearfulness - of humans, at least);

·        increased fecundity (principally through larger litters);

·        changes in dominant coat colour alleles (such as piebald and non-agouti colouring);

·        changes in reproductive timing (frequency and/or seasonality)

Keeping juvenile characters is implicated in many of the morphological traits common to all domesticates because of the very nature of the differences: smaller overall size, shortened snout, juvenile behaviour. Other traits (such as increased fecundity, docile behaviour, piebaldness, and polyestrousness), seem to be associated consequences of paedomorphosis rather than paedomorphic traits themselves.

Strange; many of these traits are just those that separate us from our hominid and ape ancestors. Stranger still, even more of them are shown by modern humans who have been 'domesticated' by large organisations, colonised for a long time, or otherwise had 'Freedom and Democracy' imposed upon them.

Crockford believes strongly that humans didn't domesticate animals from scratch - they just adopted some that had already changed in response to human presence.

"The fact that humans have been able to control and manipulate domesticates so thoroughly and with such dramatic success over the last few thousand years does not prove that the process began with the deliberate intent to do so. The most compelling of these objections, however, is that paedomorphic traits and their consequences (such as juvenile or docile behaviour, increased fecundity, small size and piebaldness) could not have been selected for by humans out of wild populations - either consciously or unconsciously - since those traits simply did not exist in the wild populations domesticates were derived from. Paedomorphic changes had to occur before selection for those traits could be used to shape future generations."

It would be difficult to take a wolf and rear a dog - that process began some 15000ya, and took a lot longer than one scientist's lifetime - or maybe it didn't - see below.

So an intriguing trial with wild silver foxes in Siberia will have to do. 

"D.K. Belyaev and his colleagues selected, from local fur farms, about 20% that were less fearful and aggressive, but still could not be handled. After a few generations, some females were in oestrus twice a year instead of just once (although it took time for the males to catch up). 

Suddenly, after just twenty generations, novel traits suddenly appeared: curled tails, floppy ears, brown piebald, and classic white piebald coat colourings.

Inexplicably, all of these traits, once they had appeared, inherited in dominant fashion. Their offspring normally had the same traits.

Animals from this generation had smaller adrenal and pineal glands, and females had higher levels of progesterone and oestradiol in early pregnancy accompanied by higher fertility than the original group.

Males had changed in minor ways to be closer in size and shape to females.

Belyaev described the animals with these novel morphological and physiological traits as also having remarkably "dog-like" behaviour: they barked and were quite unafraid of people.

Their genes hadn't mutated at all, nor had specific genes been selected, but the new 'variety' bred true. 

Small mutations within regulatory genes that operate during  embryonic development are now acknowledged as the most probable mechanism by  which large morphological changes could occur without substantial genetic change" 

Coincidence: At just about the time this experiment started, Trofim Lysenko, (1898-1976), the notorious Soviet agronomist, still led the Soviet school of genetics that opposed Mendel's law and maintained that acquired characteristics can be inherited. His theories received official support; they were taught in biology courses in the USSR and incorporated, with sometimes disastrous results, into Soviet agricultural programs. After the death of Stalin in 1953, Lysenko was strongly criticized, and his influence gradually diminished, although later he was rehabilitated by Khrushchev - to 'advise on organic fertilisers'. But perhaps he wasn’t so very far wrong, after all. 

And then, after coming up with a most powerful hypothesis into the mechanics of evolution, Crockford has the temerity to suggest how humans evolved...

"The first really plausible explanation for a number of phenomena, including the convergent evolution of bipedalism in early hominids, species-specific sexual dimorphism, coordinated changes in morphology, brain function and gut length over time in hominids, cold adaptation in Homo neanderthalensis, the possible independent evolution of H. sapiens in Asia, and regional adaptation of hominid populations.

Thyroid Hormones by themselves control both cellular and  basic metabolic rate, early embryonic cell migration and differentiation, and the expression of a  number of strategic genes. They are essential for fetal development and post-natal growth of the entire central nervous system , including the eyes and brain. In the  digestive system, THs are known to be responsible for differentiation of the epithelial lining of the small intestine (where nutrient absorption occurs) and to affect the timing of tooth eruption and tooth enamel formation. THs also function as essential co-factors in the  production and utilization of other critical hormones, and thus control function of the brain, reproductive organs, adrenal glands and hair follicles. In addition, THs control  release and utilization of growth hormones, which stimulate the liver to release insulin-like growth  factor-I (IGF-I), an important hormone shown to vary in different human and ape populations"

"When populations expand their boundaries, new  habitats offer many attractive benefits, but they also present stressful conditions for each colonizing  individual. Novel habitats are postulated as preferentially attracting physiologically stress-tolerant  individuals (those with particular TR phenotypes)  over less stress-tolerant animals. 

Stress is a ubiquitous  factor that can have purely physical manifestations (such as light or temperature), or involve a psychological or behavioral component (such as dealing with predators, new food sources or competing  for breeding sites)"

In other words, those who survive and multiply in a new environment will be those individuals who already have a slight pre-adaptation to it. Their thyroid rhythms may well carry an entrained suite of other characters, even 'maladaptive' ones, that just come with the package, and need no adaptive 'purpose', because they have none.

The thyroid rhythm 'package deal' system could explain a host of human evolution 'mysteries' without the need for all those Just So Stories:

Just So Stories, that tell us our ancestors 'evolved' something to help us on our way to becoming 'Masters of the Universe' are just that. They didn't. Our ancestors just made the best of what they had, and we just have to make the best of what they've left us. 

And much of our evolution could have happened instantaneously (in palaeontological terms) - fossil hunters will NEVER find evidence of the major changeovers.

On the other hand, who could ever have predicted that Mary Leakey's colleagues, while pelting each other with elephant dung, would have just happened on perfectly preserved 3.5 million year old human footprints at Laetoli ?

"Colonizers constitute only those individuals with stress-tolerant physiological phenotypes. Founder populations possess a non-random subset of the TR phenotypes (and the genes that produce them) maintained by ancestral populations. Variation of TR phenotypes (and the genotypes they represent) within such small founder populations will always be much smaller than that which existed in the ancestral population as a whole".

"Experimental domestication studies suggest that profound changes in behavior, reproductive physiology and morphology may occur within 20 generations under artificial selection for a stress-tolerant behavioral phenotype alone" - see Belyaev's dogs, above.

"If natural selection takes even 10-fold as long (i.e. ca. 200 years) to effect the same result, it would still be almost instantaneous in evolutionary terms—certainly too fast for paleontologists to pick up intermediate stages in the fossil record".

... and the gall to suggest that human bipedalism just happened.

Walking on two legs, when all about you were running on four, is plain daft. Indeed, as Owen Lovejoy has said: 

"Bipedality is a very serious, dangerous form of locomotion that no animal in its right mind would adopt, given the background of being a primate". 

Cleveland Plain Dealer Interview

Here are all the Just So Stories about the origin of human bipedalism:

Most of these notions suppose that bipedalism (walking upright like a man) evolved to do something, like:

• Use tools (1), carry food (2), 

• See further (3)

• Look more like a 'real man' (5), or look after the kids (9, 10).

• Scavenge or forage better (11, 14)

• Keep cool in the hot sun of the savannah (13)

• Eat better up trees (7) or on the ground (6)

• Move better (8) or further (12) than the four-legged competition.

Only the wading hypotheses (4, 15, 16) suspect that adjusting to a unique environment, where head above water, and legs doing the pushing might be best, had something to do with it, and nothing at all purposeful was involved.

Susan Crockford doesn't even worry at all about the 'purposeful' nonsense. A thyroid-driven change in body structure happened to a few apes under stress, and those who had it survived better than the rest ('Why' is for the adaptationists to argue) - to beget us.

"The earliest hominids are the Australopithecines, bipedal ancestors that appear in the fossil record at ca. 4.4 Mya. The pelvic, vertebral and femoral shape changes that allowed bipedal locomotion in Australopithecines preceded other morphological characteristics that make later hominids unique".

"This means that some incipient hominids had to have had bipedal morphology, while others did not. Bipedal traits are heterochronic in nature: they were caused by changes in developmental rates or shifts in timing of growth spurts. This strongly suggests that a heterochronic speciation event precipitated the changes associated with bipedalism, a speciation event that was very likely associated with colonization of a distinctly different habitat. 

Australopithecines evolved with a novel bipedal morphology because environmental changes pressured some of their ancestors to colonize a wooded habitat in which the prevalent foods were not the fruits they were accustomed to eating, but small animals: insects and grubs, bird eggs and fledglings, small mammals, reptiles, and amphibians. The dietary change associated with this habitat shift would have been profound, because it involved the consumption of vastly increased amounts of exogenous THs. Small prey animals, such as rodents, reptiles, amphibians and young birds, are generally eaten whole, which means that their thyroid glands (which contain especially high concentrations of THs) are consumed as well. Egg yolks of all vertebrates also contain THs.

However, herbivores or fructivores, even if they occasionally ate small animals, would have possessed a TH metabolism unprepared for such excess. Consumption of large quantities of TH-laden foods (rather than occasional small amounts), day after day and month after month, would have had a major impact on populations of incipient Australopithecines. I suggest that only those individual Australopithecine ancestors who were relatively tolerant of high stress situations would have chosen to colonize a radically new environment in the first place.

Significant changes in normal TH levels during pregnancy (either too much or too little) certainly have profound affects on the developing fetus of modern humans. There is no reason to expect that incipient Australopithecines would have responded differently to consumption of exogenous THs that far exceeded their normal intake. It is very probable that the major shift in diet proposed for incipient Australopithecines, made necessary by the change in habitat, would initially have resulted in some instances of reduced fertility (failure to ovulate or conceive, repeated miscarriages or stillbirths) and a relatively high incidence of birth anomalies of various kinds. Offspring afflicted with profound anomalies probably died young.

However, survival rates of infants with relatively minor anomalies, such as a change in pelvic and femoral shape that allowed them to stand upright with ease, may have been quite high. As long as such morphological changes did not negatively impact the survival of afflicted individuals, they would have had a reasonable chance of living to sexual maturity and passing on their genes to the next generation. 

If we view bipedalism as something akin to an unavoidable birth anomaly that could be adapted to behaviorally, it gives quite a new perspective to hominid evolution".

"Bipedal offspring would have had a good chance of having a TR (thyroid rhythm) phenotype similar to their mother, and thus would have been likely to produce bipedal infants themselves. Over the next few generations, the specific growth programs that produced bipedal morphology would have become the norm for the whole founding population. Colonization of a radical new habitat and the associated dietary switch it necessitated undoubtedly precipitated the expression of several new morphotypes, but natural selection was responsible for the fact that bipedalism was the option that survived over time".
 

"Support for this exogenous TH explanation comes from isotope analysis of Australopithecus africanus fossils from South Africa, which indicate that these first hominids consumed not fruits and leaves as often assumed, but animal prey that ate grasses".

See: Insects

Could other apes also have become bipedal for exactly the same reasons? That would send all the Just So Stories back where they belong.

"An exogenous TH explanation for the generation of bipedal morphology raises the question of whether bipedalism is exclusive to the hominid lineage. If the claims of bipedal morphology possessed by ... 4.4Mya old Ardipethecus ramidens, a newly described Australopithecine genus from east Africa at 3.5 mya, and an even older new genus from 5–6Mya deposits, Orrorin tugenensis, hold up, we will have to revise the date for the origins of hominids further still. 

The question is whether any of these genera, rather than Australopithecus, are ancestral to the line that later produced Homo sapiens: do some specimens represent cases of convergent evolution? 

If climatic change at the end of the Miocene (at ca. 5 Mya) resulted in a reduction of fruit-bearing trees in some regions of Africa—trees that had supported Miocene apes for thousands or millions of years - more than one ape lineage may have been forced to assume a diet heavily dominated by small animals. Consumption of high levels of exogenous THs would have had similar effects on any ape population as that described for Australopithecines - not identical, but similar enough to cause us confusion in sorting out the scanty fossil remains of closely related lineages. Just because Orrorin was bipedal does not automatically make it a human ancestor."

Crockford summarises her concepts in two charts, but they don't translate well from pdf format, so I have combined them into one, and jazzed them up a bit:

The Dog That Didn't Bark

I was surprised, in Crockford's paper on hominid evolution, to find the word 'iodine' mentioned only once. But there is, it seems, a substitute: exogenous (from outside). 

"THs are the only hormones that are absorbed unaltered through the digestive tract , and exogenous THs from food sources are indistinguishable from self-produced hormone."  

She argues that early hominids could, in effect, get their iodine needs from egg yolks, and from small mammals, reptiles and birds, by eating them whole, including their thyroid glands. Quite how big the thyroid gland of a small bird or reptile might be, she doesn't venture - the same problem as the theories that early hominids got their essential brainfood fatty acids from scavenged big game brains

Presumably ready-made thyroid hormones are more potent than the same concentration of 'raw' iodine from other sources, so perhaps some 'conversion factor' should be applied to take-away hormone from certain meats and eggs that wouldn't apply to, say, the 'raw' iodine in iodised salt.

"Surprisingly, however, a number of species of kelp and other algae, long known to be rich sources of iodine, were found to store much of this essential mineral as T3 and T4, providing ready-made THs to all animals that consume them – whether they have backbones or not. THs have also been found to be produced or utilized in a range of marine invertebrates, including corals and echinoderms." 

In other words, the most potent and plentiful source of exogenous Thyroid Hormones are marine foods. Take a look at the relative size of a normal mammal thyroid gland as shown on the left, and ask yourself if direct consumption of such a small organ, despite its rich store of THs, could really make much of a difference.

If this picture shows the size of a normal thyroid of a 70kg mammal, just try to imagine the size of the thyroids of Crockford's 'small rodents, reptiles, amphibians, small primates, and insects' as eaten by Homo habilis.

Most of those would have a body weight, and a corresponding thyroid weight and TH content, about three orders of magnitude less.

Chimps often eat meat, and are even occasional opportunistic hunters, but, in the 6 million years or so since their ancestors and ours parted company, they have had no rapid development of brain size or power, and in terms of evolution, seem to have 'progressed' very little, if at all. 

Crockford's thesis that Australopithecines diverged from the 'ape' line due to a much larger intake of animal foods is plausible, but that doesn't really justify why they, in turn, spent some 3 million years without evolving very much, and then diverged into two branches, one of which 'went back' to an even heavier vegetarian diet.

As meat, anyway, contains relatively little iodine (see Iodine) I wonder why Dr Crockford has plumped for

meat-eating as the prime factor in the 'spurts' of human evolution. 

At the point where humans are generally agreed to have 'emerged' from the forest of apes, grew a seriously larger brain, and, supposedly, really began to eat meat, (Homo habilis), she actually posits a decrease in TH  intake.

And... 

Now just suppose that some Australopithecines stumbled across an environment that, besides providing a diet rich in iodine and THs in bulk, and essential brain minerals, and essential brain fatty acids, was also not competed for by other 'predators', and is still a potent 'dream paradise' for over-civilised humans.

The tropical shoreline of the Old World stretches from Madagascar to Modjokerto in Java, and beyond. The same available foodstuffs (rich in all those ingredients) is virtually identical over this vast distance, and is (or was) extraordinarily abundant, as I've tried to show in these pages.

See: The Indo-Pacific Shoreline Ecotone

And it's precisely along or beyond this path that the first 'real' human (Homo erectus) remains (or symptomatic tools) have been found, from Ain Hanech in Morocco to Flores Island and Beijing.

But that's another story - meanwhile....

At each major stage in hominid prehistory, a dietary change affected hominid thyroid hormone processes, and weeded out those who couldn't cope, leaving a small founding group suited to the new dietary environment, often with quite unexpected changes in body shape, metabolism, and behaviour.

Dr Crockford has been very canny in presenting her theory on hominid evolution, by presenting it entirely, and therefore acceptably, in terms of the current orthodox paradigm - that early hominids developed in woodlands in East Africa, then progressed onto the 'savannah' and ate big game meat, and Homo erectus, tools in hand, went out of Africa to colonise the furthest reaches of Asia. Her 'take' on Neanderthals covers much of the same ground as Jerome Dobson's but reaches almost an opposite conclusion, bang in line with current palaeoanthropological (PA) opinion. 

• Her hormone-moderated evolution concepts, presented with cautious and very feminine intuition and attention to detail, and testable, will eventually become the orthodox paradigm.

• (It'll take a bit of time, though, because as every scientist in the male-dominated world of science knows, women can't think).   

Her overall hominid evolution theory is so original and persuasive that I am hijacking it wholesale for my own purposes. 

The only very minor detail  (but the main point of my Early Human Diet webpages) on which I might argue with her is exactly which diet gave early (and later) hominids the thyroid hormone boosts that changed their and their descendants' lives, forever.

  Back to Coconut Studio Index Page

Richard Parker  - Siargao Island - January  2006 (Last updated Monday, May 08, 2006)  

I welcome comments or corrections on my site and opinions, so please feel free to email me at:  richardparker01@yahoo.com