No doubt about it - human babies are fat

Compare the plump human baby with the skinny baby of our closest cousin, the chimpanzee. And, while you're about it, compare the mothers.

Born Fat

Human baby fat is quite different to human adult fat 

If you were to slice up a human baby you would find a quite amazing coverage of fat. 

Adapted from: Survival of the Fattest - Stephen Cunnane 

This MRI image shows, from left to right, row by row:

Thin covering of fat around the top of the skull

Chubby cheeks

Chubby chest and arms

Thin fat layer around upper belly

Thicker layer around mid-belly, with a lot just behind the kidneys

Much more around the buttocks and thighs

Some in the legs, and even some in the feet

Baby fat is more widely and more evenly distributed just under the skin.

Very, very little baby fat concentrates internally, around the organs of the body cavity. This is where most mammals accumulate fat stores, particularly when they are anticipating minor famine, such as in the savannah in the dry season, or winter in higher latitudes. In certain mammals, excess fat stores can 'leak out' of visceral gut and accumulate under the skin as subcutaneous fat.

In humans, too much internal body fat leads to 'beer belly' in men, and floppy tummies in women. Both are associated with diabetes, and all the other disadvantages of obesity.

Baby fat contains very low proportions of the two most common precursors to essential fatty acids - Linoleic and Alpha-Linolenic acids

But has much higher proportions of AA (Arachidonic Acid) and DHA (Docosahexaenoic Acid) - by 3-4 times the proportions found in adults.

Human babies need long-chain fatty acids (DHA and AA) to provide growth material for their brains. AA is easy to come by, but DHA isn't. See: Fats & The Brain

The linoleic and alpha-linolenic acid :arachidonic acid and docosahexaenoic acid ratio in infant body fat is almost exactly the same as it is in the human brain. Now that's a coincidence.

During the first few years of its life, a human baby will grow more fat cells (adipocytes) by about 2-3 times, and fill them up with fat by up to 14 times during their infant years. Adipocytes are basically bags of fat, and they can enlarge as necessary, although humans tend to make more of them, rather than enlarge the ones they already have. Later on, in teenage years, a human will produce a good few more adipocytes to take care of increasing fat storage needs. 

Humans grow about 10 times as many adipocytes as other primates.

Why do human babies need to be fat?

Human babies have brains and body fat each contributing to 11–14% of body weight, a situation which appears to be unique amongst terrestrial animals. 

Body fat in human babies provides three forms of insurance for brain development that are not available to other land-based species: 

(1) a large fuel store in the form of fatty acids in triglycerides - Storage fats

(2) the fatty acid precursors to ketone bodies which are key substrates for brain lipid synthesis - Ketogenesis

(3) a store of long chain polyunsaturated fatty acids, particularly docosahexaenoic acid, needed for normal brain development. Phospholipids & Fats & The Brain

The triple combination of high fuel demands, inability to import cholesterol or saturated fatty acids, and dependence on docosahexaenoic acid puts the mammalian brain in a uniquely difficult situation compared with other organs and makes its expansion in early humans all the more remarkable.

Survival of the fattest: fat babies were the key to evolution of the large human brain:, Stephen C. Cunnane, Michael A. Crawford

Not only that, to grow their brains, they need energy as well. Human babies expend some ¾ of all their incoming food energy on just maintaining their unusually huge brains at rest. 

When you're going 'Coochie-coochie coo-koo ' to the little monster, it's burning up huge amounts of energy in responding with a few uncoordinated arm-waves and a giggle. If you go on too long, it will have nothing left over to feed the need for its brain to grow. 

If there's a choice, the human body will often burn potential brain material (DHA and AA) straightaway for energy. If there's anything left over, it can be transferred to the brain to help it grow larger and more complex.

Survival of the fattest

So, to keep up its brain growth, a human infant needs a goodly reserve of essential fatty acids and extra energy in storage, and it has evolved a means of doing so - baby fat. It's a vital insurance against the times when its mother can't provide enough brain fuel to keep the baby's brain growing as it should.

Skinny human babies don't prosper.

And nor do ones who are born before they've accumulated enough baby fat to tide them over bad times. 

In the 'good old days', prematurely-born babies just died. They face a double hazard - firstly, their brain size (and the energy demand from it) is proportionately larger than in a full-term baby. Secondly, they have no body fat reserve to fuel both their brain's energy needs, and to keep warm. The essential fatty acids meant for brain structures are too often oxidised (burned) to meet heat energy demands.

Prematurity prevents appropriate fatness at birth and leads to developmental delay through childhood to adulthood (Hack et al., 1994; Crawford et al., 1997; Hack et al., 2002) Survival of the fattest

Now, they can be 'rescued' by various artificial means, but it has taken a lot of research (by the likes of Michael Crawford) to ensure they are kept warm and fed properly, and can get over the obstacle of lack of body fat reserves to develop as 'normal' human beings.

Most other species, including our closest cousins, chimps, are born in the same condition as premature human babies, without fat reserves, and with brain maturation substantially completed.

Humans cannot complete their brain maturation in the womb; they would have heads far too big to get through the pelvic opening. Uniquely, much of our brain maturation comes after birth. 

Lack of the essential minerals, iodine and iron alone, has reduced the collective intelligence of 80% of the human race by 15%. About 5 billion people are more stupid than they need be because they lack just these two little things.

Vitamin & Mineral Deficiency    A Global Progress Report 

We think we've licked the problem, at least in 'developed' countries, by iodizing table salt, but we may be dangerously complacent. At the same time as we've done that, there is a widespread campaign to reduce salt intake, so people cut the only salt they can think of. We get plenty more (if not too much), from processed foods - but that doesn't need to be iodised.

See: Iodine - Missing Ingredient

Nobody has, so far as I know, studied the effects of deficiencies in the supply of essential fatty acids (EFAs) and, in particular, DHA, over a large sample of the world's population.

Nobody has, so far as I know, studied the effects of substituting 'trans' fats - hydrogenated vegetable oils - for the good old saturated fats we consumed for 99.9999% of human history.

Nobody has, so far as I know, worked out whether human brains can tell the difference between these wholly artificial 'new fats' and the good old EFAs we've been used to for at least 2.5My. Perhaps they can't. Perhaps that's why we think we're going crazy - we probably are.

But there are pointers to at least some awareness of this problem:

Fast food awash with 'worst' kind of fat Thursday April 13, 02:30 PM

French fries and chicken nuggets from two major global fast-food chains contain very high levels of artery-clogging "trans" fats, researchers warn. And the level of trans-fats served by the chains varies dramatically from country to country

Researchers who analysed the fast food say that daily consumption of 5 grams or more of trans fats raises the risk of heart attack by 25%. Half of the 43 "large"-sized fast food meals, 24 from McDonald's and 19 from KFC, examined in the study - purchased in outlets around the world - exceeded the 5 gram level.

In a review of trans fats in the same journal, Walter Willett at the Harvard School of Public Health in Boston, US, and colleagues, conclude that in the US alone, complete removal of the industrially-produced trans fats from food preparation could prevent up to 228,000 heart attacks per year in the US.

Yahoo! News

Storage Fats

Body fat in in adults comes from dietary fats and from fats made in the body itself from excess glucose. The glucose itself comes from the conversion of carbohydrates (starches, cereals, etc). Humans can make as much as 150gms of body fat per day from these sources.

The intake of most dietary fats is in the form of triglycerides. These are broken down in the small intestine, repackaged in the intestinal wall, and sent to the liver for further processing. The liver then sends lipoproteins, rich in triglycerides, into the bloodstream. Insulin then controls the uptake of triglycerides or the release of free fatty acids by adipocytes, to balance the availability of glucose in the bloodstream.

Structural Lipids

Ketogenesis

Ever heard of this? No?

I had no idea it existed until I read the Cunnane/Crawford paper, and then Stephen Cunnane's book, and realised, with some shock, that acetone (nail polish remover) contributed somewhat to what I like to think of as my brain capacity. 

The link between infant fat stores and human brain expansion during evolution involves more than providing fatty acids for oxidation to meet energy needs. It also involves three breakdown products of fat oxidation collectively called ketone bodies (ketones; b-hydroxybutyrate, acetoacetate and acetone). There are two reasons why ketones became important to human brain evolution. 

First, the brain can oxidize ketones but it does not oxidize the fatty acids they come from. In adults, glucose is the main fuel for the brain. If food is restricted, body glucose stores (glycogen) last less than 24h. Without ketones, brain function would be rapidly compromised or muscle protein would need to be degraded to release amino acids that can be converted to glucose. Hence, ketones are an essential alternative fuel to glucose for the brain. Healthy human infants have a large store of fat that is available to make ketones. In infants, slightly elevated blood ketones are present all the time (mild ketonemia) regardless of feeding status. 

This is not the case with fed adults. In human fetuses at mid-gestation, ketones are not just an alternative fuel but appear to be an essential fuel because they supply as much as 30% of the energy requirement of the brain at that age (Adam et al., 1975). 

Second, ketones are a key source of carbon for the brain to synthesize the cholesterol and fatty acids that it needs in the membranes of the billions of developing nerve connections. 

The mammalian brain has protected itself from variations in the types and amount of fats we eat by developing the ability to: 

(i) make almost all the saturated fatty acids and cholesterol it needs

(ii) exclude most fatty acids (except certain polyunsaturates) and all cholesterol that are present in the circulation and that are available to all other organs (Cunnane, 2001). 

Since the brain requires cholesterol and saturated fatty acids in its membranes but does not take them up from the blood, it needs an abundant, water-soluble source of the carbon that accesses the brain and can be used to make these lipids. Ketones are the preferred carbon source for brain lipid synthesis and they come from fatty acids recently consumed or stored in body fat. This means that, in infants, brain cholesterol and fatty acid synthesis are indirectly tied to mobilization and catabolism of fatty acids stored in body fat. 

Hence, in all mammals studied, ketones have two important roles in the brain—they provide a reliable source of brain energy in between feeds, and they provide a major proportion of the lipid building blocks for developing brain cells. 

The uniqueness of the human situation is that babies are endowed with proportionally by far the largest ketone reserve (body fat) of any mammalian infants (Widdowson, 1974), a reserve which is suitably matched to the high energy and structural demands of the developing infant brain.

Survival of the fattest

The three ketones are: Acetoacetate, beta-Hydroxybutyrate, and ... acetone (nail polish remover). Different regions of the brain take them up selectively, and they can't supply the whole brain - hence the need for glucose as well.  They can supply up to 2/3 of the adult human's brain energy needs.

Ketone use by the brain is limited, not by the brain's ability to use them, but by their availability, meaning their availability in the form of body fat. 

They're used 5x as much by newborns as by adults, and 4x as much by older infants. This is the infant brain's insurance policy.

The brain still needs 1/3 glucose, but hasn't enough room in the skull to store it as glycogen (which needs 3-4 times its own weight in water to convert) and if glucose is in very short supply, it takes it away from other organs, or even lets them break down to provide it.

What kinds of fat do we have?

Brown Fat

Brown adipose tissue is sometimes mistaken for a type of gland, which it resembles more than white adipose tissue. It varies in color from dark red to tan, reflecting lipid content. Its lipid reserves are depleted when the animal is exposed to a cold environment, and the color darkens. In contrast to white fat, brown fat is richly vascularized and has numerous unmyelinated nerves which provide sympathetic stimulation to the adipocytes.

Brown fat cells

Brown fat is most prominent in newborn animals. In human infants it comprises up to 5% of body weight, then diminishes with age to virtually disappear by adulthood.

In contrast to other cells, including white adipocytes, brown adipocytes express mitochondrial uncoupling protein, which gives the cell's mitochondria an ability to uncouple oxidative phosphorylation and utilize substrates to generate heat rather than ATP.

Exposure to cold leads to sympathetic stimulation of brown adipocyte via norepinephrine binding to beta- adrenergic receptors. As in white fat, sympathetic stimulation promotes hydrolysis of triglyceride, with release of fatty acids and glycerol. However, within brown adipocytes, most fatty acids are immediately oxidized in mitochondria and, because of the uncoupling protein, a large amount of heat is produced. This process is part of what is called non-shivering thermogenesis.

The heat produced in brown fat can actually be imaged using a thermal (infrared) camera. If one takes such a picture of an unswaddled infant sleeping at room temperature, "hot spots" can be seen in the skin overlying brown fat deposits in the neck and interscapular area. Brown fat thermogenesis also seems to be of considerable importance to animals coming out of hybernation, allowing them to rewarm.

Brown fat

Finally, it seems that brown fat plays a non-trivial role in control of body weight, and that mitochondrial uncoupling proteins may be one of many factors involved in development of obesity. An interesting demonstration of this is found in a report in which transgenic mice with genetic ablation of brown fat developed obesity in the absence of overeating

Brown fat

If, as this suggests, most newborn animals have reserves of brown fat, then, perhaps our cousins, chimps, do too. They need something to keep them warm at night. In the interior of East and South Africa, night-time temperatures are a great deal colder than day-time ones, while, at the shoreline, the difference is very much less.

If Early Humans really did develop in the interior of places like Kenya, then why didn't they adapt, very early on, or later over a 2.5My period, a means of retaining brown fat heat reserves into adulthood to deal with cold night temperatures? 

Especially if they'd already gone to all the trouble of shedding their body hair, and standing upright to deal with the extremely high daytime temperatures of the savannah. The gentleman who thought up that one (step forward, Peter Wheeler!) did  consider that nighttime temperatures in high, arid places can be extremely cold, and then suggested that human fat covering evolved to take the place of the insulating value of body hair.

Perhaps he thought they wrapped themselves up in the leftover furry hide of lunchtime's wildebeest.

White Fat

This is the classic stuff; everyone is familiar with white adipose or fat tissue, which provides insulation and, by storing triglycerides, serves as an energy depot.

They have a thin covering of cytoplasm surrounding a single large lipid droplet. Their nuclei are flattened and eccentric within the cell.

The usual models for human fat studies -- rats and mice -- are inappropriate because they have relatively large adipocytes which then expand and reduce as total fat goes up and down.

Humans, as other primates, have relatively small adipocytes and tend to add more as they can't expand as much as those of rats and mice. This makes it harder to lose total fat compared to those rodents. This feature, relatively small and numerous adipocytes, is common to humans, fin whales, hedgehogs, monkeys, and badgers.

White fat - as shown in Brown fat

Fat Composition

Triglycerides (or triacylglycerols) are glycerides in which the glycerol is esterified with three fatty acids. They are the main constituent of vegetable oil and animal fats.

Chemical structure

Chain lengths of the fatty acids in triglycerides can be from 4 to 22 C atoms, but 16 and 18 are most common. Shorter chain lengths are found in butter for instance. Almost without exception, only even numbers of carbon atoms are found in natural fatty acids - due to the way they are bio-synthesised from acetic acid.

Metabolism

Triglycerides play an important role in metabolism as energy sources. They contain twice as much energy (8000 kcal/kg) as carbohydrates. In the intestine, triglycerides are split into glycerol and fatty acids (with the help of lipases and bile secretions), which can then move into blood vessels. The triglycerides are rebuilt in the blood from their fragments and become constituents of lipoproteins. Various tissues can release the free fatty acids and take them up as a source of energy. Fat cells can synthesize and store triglycerides. When the body requires fatty acids as an energy source, the hormone glucagon signals the breakdown of the triglycerides by hormone-sensitive lipase to release free fatty acids.

Wikipedia article "Triglyceride".

Elevated triglycerides in the blood have been positively linked to proneness to heart disease, but these triglycerides do not come directly from dietary fats; they are made in the liver from any excess sugars that have not been used for energy. The source of these excess sugars is any food containing carbohydrates, particularly refined sugar and white flour.

In short, in the 10,000 years since we all switched from eating anything good that we could find, to getting most of our energy from grass seeds (wheat, maize and rice), we've not only deprived ourselves of essential brain foods, but given ourselves the opportunity to become obese as well.

In addition, during the 20th century, there has been a huge (and very well funded and orchestrated) push for us to eat more 'trans' fats - hydrogenated cheap vegetable oils. It's been estimated that these fats kill nearly a quarter of a million Americans per year. That would normally be known as mass homicide.

We're facing a double whammy - crap carbohydrate energy foods plus crap fat energy foods.

'Health nuts' started to realise there was something wrong 50 years ago, and took to eating salads and mineral water - you would do better (and cheaper) to just starve.

If you want to live until Armageddon (coming soon, as some nutters will tell you) buy a few thousand cans of sardines in olive oil, and hunker down.

Are humans fat?

Caroline Pond, perhaps the world's leading body fat scientist, says 'Yes':

(Her quotes are extracted from Jim Moore's anti-AAT website, and Algis Kuliukas' pro-AAT website)

Our recent observations on captive monkeys suggest that adipose tissue may grow in very different ways in rodents and in primates. The obese monkeys had more than 10 times as many adipocytes as slim monkeys of the same age, but the average sizes of the cells were similar in specimens of 5 per cent fat and those of 25 per cent fat. The fatter monkeys simply had more adipocytes; increases in the volume of cells contribute little to the growth of adipose tissue. The cellular mechanism of growth of adipose tissue in monkeys is thus fundamentally different from that of young laboratory rodents. Adipocytes probably do not normally expand more than about fourfold, but there is no obvious upper limit to the numbers of new cells that can be formed.  Perhaps that is why the fatness of well-fed monkeys and humans is so much more variable than that of laboratory rodents, and why we primates are more susceptible to massive obesity than rats and guinea pigs.

Badgers, hedgehogs and hamsters are among the few common wild mammals that normally accumulate large quantities of fat. In such species, the superficial depots enlarge disproportionately as they fatten, so that specimens above about 15 per cent fat -- the same fatness as "slim" humans -- seem to have an almost continuous layer of adipose tissue between the skin and the muscles. In other words, humans are just one example among several naturally obese mammals in which the superficial adipose depots are relatively massive.

Caroline Pond - as quoted in: Fat - Jim Moore

The sparse data on the ‘natural’ distribution and abundance of adipose tissue in primates show that the basic anatomy of human adipose tissue  is similar  to that of terrestrial  monkeys, and so was probably inherited  directly from their primate  ancestors. Superficial  adipose tissue appears to extend over a greater area of the body in humans than in other terrestrial mammals because of changes in the proportions of the limbs and in the shape of the girdles, the dorso-ventral flattening of the thorax and abdomen and the bipedal posture of  the hip, knee and shoulder. The contrasts between humans and of her primates have parallels in other mammals, and may be a direct  consequence  of the increased abundance of adipose tissue, which itself may be of very recent origin.

Caroline Pond - as quoted in: Fat- Algis Kuliukas

Fat - Ancient or Modern?

There's no way, yet, that soft tissues, like flesh and fat, can be detected from fossil bones. Having said that, I hope I may be pleasantly surprised by some chance extraordinary discovery, like the fossilised footprints at Laetoli, or the feathers found on Archaeopteryx fossils, and countless dinosaurs since. Perhaps an early human is waiting to be found, encased in volcanic ash like some unfortunates at Pompeii, with a complete cast of his body shape.

It certainly seems that prevalent adult obesity in general dates from the time our diet changed to mainly carbohydrate energy sources following the introduction of agriculture, and prevalent gross obesity seems to be closely related to our adoption of 'processed' foods and a sessile life, in office, car, and home, in the 20th century.

But then there are the 'Venus' figures, and there are many, made long before agriculture was known. Sure as eggs is eggs, someone will find a 'Bacchus' figure of a fat male.

And there is the fact, made throughout this web page, that human babies, at least, needed to be born fat from the earliest stages that their brains grew in size beyond the 'mammalian norm', and kept on growing.

As always, sex comes into the story

Humans start off very fat, drop within a few years to the leanest condition of our lives as children, and then rapidly build up fat at puberty, with radical differences in quantity and distribution of fat between boys and girls. To top it off, at middle age our fat distribution changes once again. These are classic telltale signs of a trait which has been shaped by sexual selection rather than by adaptation to our environment.

Fat - Jim Moore

Why did babies grow fat? Another chicken and egg puzzle.

You might almost be persuaded that human baby fat has evolved its exceptional abundance and exceptional composition just to help its brain grow. 

That would be a perfect Just-So story.

Cunnane and Crawford have a more persuasive answer:

How did early humans acquire the unique ability to deposit fat on the fetus during pregnancy? No one knows for sure but this key attribute can only have arisen because some hominid clades were exposed to a diet containing both high energy and nutrient density for a sufficiently long time that pre-existing genes were expressed which were capable of promoting human subcutaneous fetal fat cell development and metabolism in hominid fetuses.

The abundant ... diet was the first real opportunity in hominid evolution to deposit extra dietary energy as fat, and it occurred at all ages, including during pregnancy and in the third trimester fetus. Non-human primates deposit body fat if they are relatively inactive, i.e. if they are captive, have an abundant high-energy diet, and have little need to exercise or escape predators. 

This is a rare combination in the wild. Even in captivity, they (apes) deposit fat mainly around abdominal organs as well as under the skin of the trunk and limbs. Abdominal fat deposition in adult humans and captive mammals is distinctly unlike that in human term infants who have ~90% of their fat under the skin and almost none surrounding the visceral organs (Harrington et al., 2002).

The easy accessibility and abundance of ... food would have been as important as the high energy value of these foods to pre-human hominids because it would have meant less energy would have been expended in foraging over large distances. This would facilitate accumulation of fat, especially during pregnancy and lactation. 

Initially, the increasing fatness in babies of early hominids would simply have been a fortuitous consequence of the higher quality and more reliable ... food supply.

... human evolution does not eliminate hunting, whether for insects, carrion, or big game, nor does it reject edible fruit, nuts, roots, or termites as valuable components of the diet right up to the present. However, diets that exclude ... foods were insufficiently reliable, accessible or nutritious to have permitted brain expansion similar to that seen in humans or it should have happened to a similar extent in at least one other non-human primate species.

Contrary to the prevailing idea of hominids eking out subsistence under adverse conditions, we believe human brain evolution depended on finding an abundant, reliable and nutritious food supply. 

With the right genetic predisposition, a sustained improvement in diet would have allowed evolution of a marginally bigger brain but with two important caveats: 

- It would have had no specific functional advantages

- Such improvements could not have been needed for survival

Over a long period and if they were lucky, natural selection of those with somewhat bigger brains would conceivably lead to a modest improvement in hominid intelligence. A larger, more sophisticated brain would undoubtedly have helped improve hunting skills but wasn’t necessary for survival because there was always a high quality diet nearby to keep the genes for brain expansion expressed if the hunt didn’t go well.

Survival of the fattest

I've edited the text above. Each '...' originally read 'shoreline' but I decided that too much repetition of that particular word would bore you, and detract from the message I'm trying to send.

No animal needs to, or can evolve to survive. They either do or they don't. 

The very ideas of the 'struggle for existence', 'Nature red in tooth and claw', etc, -only go back a very few years in human history, to Herbert Spencer (inspired by Alfred Tennyson's phrase, used in passing, as he mourned his boyhood love) and Raymond Dart, a colonial Australian in colonial South Africa, who became, quite justifiably, angry about the acceptance (or not) by the British 'Establishment' of his finding of the very earliest human fossil in the first half of the 20th century, while they were still prattling on about a complete fake, "Piltdown Man".

Cunnane and Crawford do it nicely - there was no need at all for anything to force humans, and above all, no final objective to make them to become what we are; they enjoyed a plentiful life, and were merely brushed by the winds of change, very occasionally, over a very long period.

'Parsimony' is a word much employed by scholars who wish they were scientists, in the Popperian sense, where a theory can be 'disproven' by alteration of just one critical (and very real) factor.  

Amongst palaeoanthropologists, John Hawks uses the word, as a club, wielded in a very clumsy way:

Evaluating the parsimony of hypotheses is a fundamental aspect of the scientific method. The idea is that hypotheses differ with respect to the kind of assumptions that the (sic) requires to make. Some hypotheses require a large number of assumptions, others require fewer assumptions. Some hypotheses require fairly extraordinary assumptions.

There can be no 'scientific method' in a field of study that can only build, conjecture upon conjecture, until it has such a towering house of cards that any alternative ideas are seen as threats to its very foundations and have to be ridiculed or dismissed.

To give an example - the judgement that one early fossil - Ardipethecus ramidus, was already bipedal rests on the find of a single toe bone.

Does the hypothesis that certain apes, driven out of thick and fruitful forests by aridity and encroaching grasslands, stood upright, lost their body hair to keep cool, learned to make stone tools, learned to hunt or scavenge large animals, changed their basic diet from fruits and nuts to barely more nutritious meat, learned to cooperate to make the best of hunted or scavenged carcasses, reduced their gut sizes, and so grew brains - really make sense? Is it in the least bit parsimonious?

Little of it is provable or not - the accepted 'Human Story' is conjecture, conjured up from remarkably little real evidence.

So, sit back and enjoy a much much more comfortable ride.

Infants floating?

Conclusions

The reason that I tag Cunnane and Crawford's view of the circumstances of human brain evolution as 'A Persuasive Answer' is that it is one of the first explanations that I've come across that is not teleological, ie, it doesn't assume brain evolution was in any way directed, and at least in the earliest stages, was not somehow geared towards the higher human intelligence that is its most obvious attribute today. They've completely bypassed  the 'Chicken & Egg problem.

Mof the content of this webpage is straightforward factual facts, leading to very well-founded conjectures (mainly by others, I would add, not me).  None of the facts has been shoehorned into the straitjacket of a 'well-known' paradigm.

Much of the material for this webpage , and for Fats & The Brain 1 - Why DHA matters comes directly from the writings of Michael Crawford and Stephen Cunnane.

Both cooperated on a seminal paper: