Stop Fearing Carbohydrates? New Research Says Sugar Helped Build the Human Brain

For decades, one of the most familiar stories about human evolution has gone something like this: our ancestors started eating more meat, gained access to concentrated protein and fat, and suddenly had enough energy to build much larger brains.

A major new analysis published in Science argues that this story is incomplete.

The human brain does not run primarily on protein. Under ordinary physiological conditions, its preferred fuel is glucose. As the brains of our ancestors expanded dramatically over millions of years, their glucose requirements would have increased as well. Researchers from the University of Sydney and the University of Glasgow therefore asked an unusually simple question: where was all that glucose coming from?

Their answer points toward foods that often receive surprisingly little attention in popular accounts of the “Paleo” diet: fruit, honey and eventually cooked starch-rich plants such as underground tubers.

The study, titled A central role for dietary sugars in human evolution, was published in Science on August 6, 2026. Led by nutrition scientist Jennie Brand-Miller with Karen Hardy, David Raubenheimer and Les Copeland, it models changing carbohydrate availability and glucose requirements across roughly four million years of hominin evolution.

Its conclusion is not that meat was irrelevant.

Nor does it say our ancestors survived on candy-like quantities of sugar.

Instead, it proposes something more interesting: animal foods and carbohydrate-rich plant foods probably played complementary roles in human evolution, and the importance of glucose has been underestimated.

That distinction matters because the word “sugar” means something very different in an evolutionary landscape filled with ripe fruit and occasional honey than it does in a modern supermarket filled with soft drinks, confectionery and refined snacks.

The New Science Study at a Glance

The 2026 paper argues that:

• Human brain expansion created steadily increasing glucose demands.
• Early hominins probably obtained substantial carbohydrate energy from fruit and other naturally sweet foods.
• Honey may have provided an unusually concentrated source of sugars when available.
• Increasing consumption of animal foods remained important for protein, fat and micronutrients.
• Cooking later increased access to digestible starch from underground storage organs and eventually other plant foods.
• Pregnancy, fetal growth and lactation imposed additional glucose requirements that may have influenced dietary evolution.
• Children’s unusually energy-demanding brains may help explain humans’ strong preference for sweet tastes.
• Modern nutritional lessons should emphasize carbohydrate quality, not simply carbohydrate avoidance.

The paper therefore challenges the idea that there was one magical food that “made us human.”

Human evolution was almost certainly nutritionally more complicated than that.

Our Brains Became Exceptionally Expensive Organs

The human brain is metabolically expensive.

Although an adult brain represents only a small proportion of total body mass, it accounts for a substantial share of resting energy use. Growing children face an even more remarkable energetic burden. Research on childhood metabolism has estimated that brain glucose use can peak at the equivalent of roughly 66% of resting metabolic expenditure around early childhood.

That is an important correction to a claim often repeated in popular summaries.

It does not mean a child’s brain routinely consumes two-thirds of all calories eaten during the day.

A 2019 analysis distinguished the measures clearly: at its lifetime peak, childhood brain metabolism corresponds to roughly 66% of resting metabolic rate and about 43% of total daily energy requirements.

Even so, the number illustrates an extraordinary evolutionary problem.

Brains are expensive.

Bigger brains are even more expensive.

The new Science study models a lineage in which brain mass rose from roughly 300 grams in early hominins such as Australopithecus afarensis to approximately 1,500 grams at the modern-human end of the authors’ evolutionary model.

Something had to pay that metabolic bill.

The Missing Question: Where Did the Glucose Come From?

Protein receives enormous attention in modern diet culture.

But protein is not the brain’s preferred everyday fuel.

The brain normally depends heavily on glucose, while other glucose-dependent tissues include red blood cells and portions of the kidneys. Pregnancy and lactation introduce further demands through the fetus, placenta and mammary glands.

Humans can manufacture glucose through processes such as gluconeogenesis, including from certain amino acids and other substrates.

But the existence of that pathway does not make dietary carbohydrates biologically irrelevant.

Brand-Miller and her colleagues focused on what they call obligatory glucose demand: the glucose requirements of tissues whose metabolic needs would have had to be satisfied as brains and bodies changed throughout hominin evolution. They then compared those needs against plausible dietary resources across six evolutionary stages.

The researchers combined evidence from multiple disciplines, including:

• Human physiology
• Metabolism
• Food composition
• Primate diets
• Dental morphology
• Fossil isotope evidence
• Archaeology
• Genetics

This is therefore not a fossil discovery showing a bowl of prehistoric fruit salad.

It is a model-based synthesis of existing evidence.

That distinction is crucial.

The Study Does Not Prove Sugar “Caused” Big Brains

Popular headlines inevitably simplify research.

“Sugar made the human brain” is catchy.

Scientifically, it is too strong.

The researchers did not experimentally demonstrate that eating a particular amount of fruit caused hominin brains to expand.

Instead, they argue that the energetic requirements of expanding brains are compatible with substantial carbohydrate consumption and that carbohydrate-rich foods deserve a larger place in explanations of human dietary evolution.

Brain evolution involved many interacting pressures, potentially including:

• Diet
• Foraging complexity
• Social organization
• Environmental variability
• Tool use
• Cooperation
• Development
• Life-history changes
• Food processing

No single nutrient explains all of human cognition.

The new study is important because it restores an overlooked part of that equation.

Fruit May Have Been Far More Important Than the Popular “Caveman Diet” Suggests

Our early hominin ancestors did not suddenly appear as spear-carrying hunters.

The lineage inherited a much older primate dietary history.

The new analysis uses chimpanzee-like dietary patterns as one reference point and concludes that the earliest stages were strongly dependent on plant foods, particularly fruit. Science News reports that the model places more than two-thirds of dietary energy in the earliest chimpanzee-like stage as coming from fruit-rich diets.

Fruit provides several things simultaneously:

• Glucose and fructose
• Water
• Fiber
• Vitamins
• Minerals
• Phytochemicals
• Readily accessible energy

Importantly, saying that a large percentage of food energy came from fruit is not the same as saying the same percentage came from pure sugar.

Fruit contains water, fiber and many other components.

The researchers’ reconstructed hominin diets suggest that natural sugars themselves may have supplied roughly 20% to 35% of dietary energy during major phases of hominin evolution, while the balance shifted as animal foods and starches became more important.

That is a very different image from a prehistoric human living almost exclusively on steaks and leafy vegetables.

Why Fruit Could Have Influenced Brain Evolution in More Than One Way

Fruit may have mattered not only because it contained calories.

Finding ripe fruit is cognitively demanding.

Fruit resources change with:

• Geography
• Season
• Rainfall
• Ripeness
• Competition
• Plant species

A forager benefits from remembering where particular trees are located, when they produce fruit and which routes efficiently connect scattered resources.

Brand-Miller pointed to earlier research linking fruit consumption in primates with relatively larger brains and suggested that locating seasonal fruit may itself have rewarded memory and cognitive flexibility.

This creates an intriguing evolutionary possibility.

Fruit could simultaneously have:

1. Provided fuel for metabolically expensive nervous tissue.
2. Rewarded cognitive abilities useful for locating that fuel.

That does not prove a simple feedback loop, but it helps explain why fruit deserves more attention in discussions of primate and human brain evolution.

What About Honey?

Honey is another fascinating part of the hypothesis.

Unlike most plant foods, honey contains a high concentration of readily available sugars.

For hunter-gatherers able to locate wild bee colonies, it could provide an exceptionally dense burst of carbohydrate energy.

Brand-Miller argues that honey should not be dismissed historically as nutritionally meaningless “empty calories.” In an ancestral environment where concentrated energy was difficult to obtain, honey could have been a valuable resource.

But there is an important modern distinction.

Evolutionary value does not equal unlimited modern health benefit.

For ancient foragers, honey was difficult to find, seasonally constrained and expensive to obtain.

Modern humans can buy kilograms of concentrated sugar without climbing a tree, searching kilometers of landscape or dealing with angry bees.

That radically changes the nutritional context.

Meat Still Matters

The new study does not overthrow the importance of meat in human evolution.

Brand-Miller explicitly describes the carbohydrate and animal-food hypotheses as parallel rather than mutually exclusive. Animal foods are nutrient dense and likely contributed substantially to the evolution of later hominins.

Meat and other animal foods can provide:

• Protein
• Fat
• Iron
• Zinc
• Vitamin B12
• Other micronutrients
• High caloric density

Evidence of increasing meat consumption becomes particularly important from roughly the emergence and expansion of early Homo onward.

The error is turning that into:

Meat alone built the brain.

Evolution does not require that one food defeat another.

An omnivorous strategy allowing humans to obtain energy and nutrients from diverse sources may have been one of our lineage’s greatest advantages.

“Meat Versus Carbohydrates” Is Probably the Wrong Debate

Suppose early humans gained increasing access to both animal foods and energy-rich plants.

Those resources would solve different nutritional problems.

Animal foods could contribute high-quality protein, fats and micronutrients.

Carbohydrate-rich foods could supply glucose relatively efficiently.

Food processing could increase access to energy from otherwise difficult plants.

The combination could support:

• Larger brains
• Larger bodies
• Longer childhoods
• Pregnancy
• Lactation
• Physical activity
• Survival during variable food availability

The new paper therefore argues for a more complete model rather than a dietary winner.

The Pregnancy Problem Makes Carbohydrates Even More Interesting

One of the paper’s most important arguments has received less attention than the headlines about fruit.

Reproduction is energetically expensive.

A pregnant female must support:

• Her own brain
• Her other glucose-dependent tissues
• Fetal development
• The placenta

After birth, lactation adds further metabolic demands.

The researchers modeled these requirements and concluded that reproductive females would have experienced especially high glucose needs as hominin brain and body sizes increased.

That changes the evolutionary question.

Instead of asking only:

“What fuel did an adult male hunter need?”

we also need to ask:

“What diet allowed pregnant and breastfeeding females to successfully produce and raise increasingly large-brained offspring?”

Evolution depends on successful reproduction.

A dietary theory that cannot support mothers and developing children is incomplete.

Children May Explain Why Humans Love Sweetness

Humans are born with a strong attraction to sweet tastes.

The new study argues that this preference makes evolutionary sense.

A child’s growing brain demands enormous amounts of energy relative to the rest of the body, particularly around early childhood.

In an ancestral environment, sweetness usually signaled a potentially valuable energy source.

Ripe fruit is sweeter than unripe fruit.

Honey is intensely sweet.

Detecting sweetness could therefore guide children and adults toward calorie-rich foods.

A strong preference for sweet tastes would not necessarily have been maladaptive when concentrated sugar was difficult to obtain.

The modern problem is that humans carried the preference into an environment unlike anything natural selection prepared us for.

Evolution Gave Us a Sweet Tooth—Industry Gave It Unlimited Access

Our ancestors could not buy a two-liter bottle of sugary drink.

They could not open a packet containing refined starch, added sugar and fat within seconds.

The ancestral relationship between sweetness and food quality was therefore very different.

In fruit, sugars usually arrive with:

• Fiber
• Water
• Micronutrients
• Cellular plant structure

Modern refined foods can provide large quantities of rapidly available carbohydrate while removing much of that structure.

The University of Glasgow’s Karen Hardy specifically cautions that refined sugars in sweets and snacks differ substantially from sugars consumed within whole fruit, and that excessive amounts of rapidly digested carbohydrates can contribute to modern health problems.

So the evolutionary lesson is not:

Sugar is good, therefore eat more candy.

It is:

Carbohydrates were important enough in human evolution that treating the entire macronutrient category as biologically unnecessary makes little sense.

Then Came Starch

Fruit and honey are not the only carbohydrate sources available to humans.

Plants store carbohydrate as starch.

Potential ancestral sources included underground storage organs such as:

• Tubers
• Roots
• Rhizomes

These foods offered a major advantage: unlike ripe fruit, many underground resources could be available when above-ground foods were scarce.

But starch presents a processing problem.

Some raw starches are relatively resistant to digestion, and cooking can greatly increase starch gelatinization and accessibility to digestive enzymes.

This is where fire potentially transformed the human energy economy.

Cooking Opened a New Carbohydrate Reservoir

The researchers argue that once cooking became available, humans could obtain more glucose from starchy plant foods that were otherwise harder to digest efficiently. Their examples include underground foods such as wild yams, water-lily rhizomes and African potato.

Heating can break down plant structures and alter starch in ways that make it easier for digestive enzymes to access.

This expanded the menu.

Instead of depending heavily on fruit for carbohydrate energy, later humans could increasingly draw glucose from cooked starch.

That may have been particularly valuable when fruit was seasonal or scarce.

But the Timing of Fire Is Still Debated

This is one place where the new evolutionary model should not be presented as settled fact.

Exactly when hominins began regularly controlling fire and cooking food remains debated.

There is evidence suggesting very old interactions with fire, but demonstrating habitual cooking is harder than demonstrating that fire existed at an archaeological site.

Outside researchers commenting on the new study have noted that hominins with already substantially enlarged brains existed before evidence for routine cooking becomes unequivocal. Science News likewise emphasizes that much human brain enlargement preceded secure evidence for cooking.

That actually strengthens one part of the new argument.

If large brains began developing before cooked starch became consistently available, earlier carbohydrate sources such as fruit and honey become even more interesting.

But it also means we should avoid a neat sequence in which humans “mastered fire” at one exact moment and immediately switched to tubers.

Evolutionary transitions are rarely that tidy.

What About Amylase?

Humans possess enzymes called amylases that break starch into smaller carbohydrates.

Salivary amylase starts this process in the mouth, while pancreatic amylase continues it in the digestive system.

Changes in human starch digestion have long been discussed as evidence that carbohydrate-rich foods mattered in our evolutionary history.

The 2026 Science paper builds on this broader body of evidence rather than inventing the carbohydrate hypothesis from scratch. The new contribution is its attempt to model glucose demand across a much longer evolutionary sequence and connect fruit sugars, reproduction and later starch use within one framework.

Did Paleo Humans Eat Mostly Meat?

There was no single “Paleo diet.”

The Paleolithic spans an enormous range of:

• Time
• Geography
• Climate
• Human species
• Technologies
• Available plants
• Available animals

A population living near a tropical forest would encounter a radically different menu from humans living in Ice Age Eurasia.

Some hunter-gatherer groups undoubtedly depended heavily on animal foods.

Others had greater access to:

• Fruit
• Tubers
• Seeds
• Nuts
• Honey
• Grains
• Legumes or other plant foods

Even the 2026 study models shifting plant-to-animal proportions rather than one permanent ancestral diet.

So a modern dietary program marketed as “Paleo” should not automatically be treated as a precise reconstruction of what all prehistoric humans ate.

There was no universal prehistoric meal plan.

Did Our Ancestors Eat Grains?

The popular claim that grains are purely a post-agricultural invention also needs nuance.

Agriculture eventually made cereal grains far more abundant and reliable, but wild grains existed before farming.

The University of Sydney researchers note that grain consumption became important relatively late compared with fruit and underground plant foods in their evolutionary model.

The broader point is that carbohydrate evolution did not begin with bread.

For millions of years before agriculture, carbohydrate could come from sources including:

• Fruit
• Honey
• Roots
• Tubers
• Rhizomes
• Other edible plant tissues

Equating “carbohydrate” exclusively with pasta, white bread and breakfast cereal therefore makes little evolutionary or nutritional sense.

Carbohydrate Is a Chemical Category, Not One Food

Modern nutrition arguments often treat all carbohydrates as though they were interchangeable.

They are not.

The carbohydrate category includes foods as different as:

• Lentils
• Apples
• Oats
• Potatoes
• Brown rice
• Beans
• Soft drinks
• Cake
• Candy

All contain carbohydrate, but their nutritional profiles differ dramatically.

They may vary in:

• Fiber
• Protein
• Vitamins
• Minerals
• Food structure
• Digestion rate
• Added sugars
• Caloric density
• Satiety

This is why modern dietary guidance increasingly emphasizes carbohydrate quality rather than simply carbohydrate quantity.

What Does the World Health Organization Say About Carbohydrates?

Current WHO guidance does not recommend avoiding carbohydrates.

Its 2026 healthy-diet guidance states that, for most people, a substantial proportion of dietary energy can come from unrefined carbohydrates and recommends that carbohydrate sources primarily consist of:

• Whole grains
• Vegetables
• Fruits
• Pulses such as beans, chickpeas, lentils and peas

WHO also recommends limiting free sugars to less than 10% of total energy intake, with further reduction potentially providing additional health benefits.

That distinction is perfectly compatible with the evolutionary story.

Carbohydrates are not the enemy.

Unlimited refined sugar is not the same thing as carbohydrate-rich whole food.

Honey Creates an Interesting Modern Paradox

Honey may have been evolutionarily valuable.

That does not place it in the same modern nutritional category as whole fruit.

WHO classifies sugars naturally present in honey, syrups and fruit juices as free sugars for the purpose of its intake recommendations.

Why?

Because a modern spoonful of honey provides concentrated sugar without the intact cellular fiber structure of whole fruit.

So two statements can both be true:

Honey may have been an important high-value energy source during human evolution.

And:

Modern people should not interpret that history as permission to consume unlimited honey.

Evolution describes what helped ancestors survive and reproduce.

Nutrition science asks what helps modern people remain healthy in today’s environment.

Those are related questions, but they are not identical.

Does the Brain Need Dietary Carbohydrates?

This question requires precision.

The brain normally relies heavily on glucose.

But that does not mean every molecule of glucose must come directly from eating carbohydrate.

During prolonged carbohydrate restriction or fasting, the human body can produce glucose internally and the brain can increase its use of ketone bodies.

That is why humans can survive on diets containing very low amounts of carbohydrate under certain circumstances.

But survival without much dietary carbohydrate does not demonstrate that carbohydrates were evolutionarily unimportant.

The 2026 paper addresses what dietary strategy plausibly supplied the energetic requirements of expanding brains over evolutionary time—not whether modern humans possess metabolic pathways that can compensate during carbohydrate scarcity.

Those are different questions.

Does This Disprove Keto?

No.

The paper is about human evolution, not a clinical trial comparing ketogenic and higher-carbohydrate diets.

Ketogenic diets have established medical applications and are also used voluntarily by some people for weight management or other goals.

Nothing in the Science analysis demonstrates that every modern person must eat a high-carbohydrate diet.

Likewise, the fact that humans can function in ketosis does not prove carbohydrate foods were insignificant during evolution.

A species can possess metabolic flexibility precisely because its ancestors encountered changing food environments.

Does It Disprove the Paleo Diet?

Again, not exactly.

“Paleo diet” refers to a modern collection of dietary philosophies rather than one scientifically established prehistoric menu.

Some versions already include:

• Fruit
• Root vegetables
• Nuts
• Seeds
• Honey

Those versions are not contradicted simply by showing that ancestral humans consumed carbohydrate.

The new findings are more damaging to a popular caricature of Paleolithic eating in which prehistoric humans supposedly lived on enormous quantities of meat while carbohydrates played little meaningful biological role.

That caricature becomes increasingly difficult to defend.

The Meat-Focused Fossil Record May Be Biased

There is another fascinating reason meat can dominate stories about human evolution.

Bones preserve.

Stone tools preserve.

But fruit does not preserve nearly as conveniently.

An archaeological site containing butchered animal bones and stone cut marks provides dramatic evidence of meat processing.

A ripe berry eaten two million years ago usually leaves nothing comparably obvious.

University of Oxford archaeologist Julie Lee-Thorp, commenting on the new paper, suggested that modern assumptions about meat as a high-status food may also influence the questions researchers emphasize.

UCLA anthropologist Brian Wood offered an important counterpoint: human-evolution research has long recognized diverse high-quality foods rather than focusing exclusively on meat. He argues that the broader adaptive advantage may have been our ancestors’ ability to exploit many difficult-to-acquire resources—including meat, fruit, honey, nuts and underground plants.

That is probably the most useful debate generated by the paper.

Not “fruit beat meat.”

But:

Have we underestimated the diversity of foods required to build a human?

Human Evolution May Be a Story of Dietary Flexibility

Modern humans live successfully in radically different food environments.

Traditional diets have ranged from high-carbohydrate tropical diets to extremely animal-heavy diets in environments where edible plants were seasonally limited.

That flexibility is itself remarkable.

Our physiology can process:

• Starch
• Sugars
• Protein
• Fat

Our behavior adds another advantage: we process food culturally.

Humans:

• Cook
• Grind
• Ferment
• Dry
• Soak
• Roast
• Store
• Share

Food culture allows us to obtain energy from resources that might otherwise be difficult to exploit.

The success of Homo sapiens may therefore be explained less by discovering one “perfect” food and more by becoming unusually good at combining many foods.

The Study’s Biggest Strength Is Also Its Limitation

The new paper covers roughly four million years.

That scale allows researchers to ask enormous questions.

But the deeper we travel into the past, the less direct evidence survives.

The model necessarily depends on assumptions about:

• Food availability
• Body size
• Brain size
• Plant-to-animal ratios
• Digestibility
• Metabolic requirements
• Fire use

The authors integrate a wide range of evidence, but modeling cannot transform uncertain prehistoric variables into perfect knowledge.

Independent researchers have already highlighted assumptions that deserve further scrutiny, including the timing of fire and the extent to which different ancestral populations depended on specific food sources.

The study should therefore be read as an important argument, not the final word on four million years of diet.

The Study Is a Reframing, Not a Revolution Against Everything We Knew

The strongest interpretation of the research is surprisingly moderate.

Animal foods mattered.

Plant foods mattered.

Energy mattered.

Glucose mattered.

Reproduction mattered.

Cooking mattered.

Different resources became important at different moments.

That may sound less dramatic than saying “sugar created humanity,” but it is scientifically much more interesting.

Evolution does not need one hero nutrient.

What Should Modern Humans Actually Learn From This?

The evolutionary lesson is not to recreate a theoretical Australopithecus menu.

Our lives are different.

Our lifespans are different.

Our physical activity is different.

Our food supply is radically different.

Most importantly, highly refined foods are available at a concentration and consistency our ancestors never experienced.

The practical lesson supported both by the new research and current nutrition guidance is simpler:

Do not confuse carbohydrates with refined junk food.

High-quality carbohydrate foods can include:

• Whole fruit
• Vegetables
• Beans
• Lentils
• Chickpeas
• Whole grains
• Minimally processed starchy foods

WHO recommends precisely these types of foods as preferred carbohydrate sources.

“Stop Fearing Carbs” Needs One Important Footnote

There is a temptation to turn the study into another nutrition slogan:

Carbs made your brain, so eat all the carbs you want.

That would simply replace one oversimplification with another.

Carbohydrate quality matters.

Total energy intake matters.

Individual metabolic health matters.

Medical conditions matter.

Food preparation matters.

WHO distinguishes strongly between carbohydrate-rich whole foods and excessive free sugars.

The best takeaway is therefore:

Stop treating carbohydrates as inherently unhealthy—but do not treat all carbohydrate foods as nutritionally equivalent.

Refined Sugar Is Not an Evolutionary Superfood

Our ancestors’ attraction to sweetness may have improved their ability to locate valuable calories.

Modern food manufacturing can exploit exactly that preference.

The environment has changed faster than our biology.

In nature:

Sweetness might lead to a ripe mango.

In modern life:

Sweetness might lead to a liter of sugar-sweetened beverage.

The sensory signal is similar.

The nutritional package is not.

This is why evolutionary history cannot be used to argue that consuming large quantities of refined sugar is healthy.

WHO continues to recommend limiting free sugars while encouraging fruits, vegetables, whole grains and pulses.

What the Study Really Does to the Popular Paleo Narrative

The new research does not demolish all forms of Paleo eating.

It demolishes a simplistic myth:

Humans became intelligent because our ancestors abandoned carbohydrate-rich plant foods and became predominantly meat eaters.

The evidence increasingly favors something more nuanced.

Our ancestors were adaptive omnivores.

Meat added valuable nutrients.

Fruit supplied readily available carbohydrate.

Honey offered concentrated energy.

Underground storage organs provided another resource.

Cooking eventually expanded access to starch.

Different environments favored different combinations.

Evolution rewarded flexibility.

Perhaps We Became Human Because We Refused to Eat Just One Thing

This may ultimately be the most interesting interpretation.

Chimpanzees can eat animal foods.

Many animals eat fruit.

Others dig roots.

Some raid bee nests.

The defining feature of humans may not have been the discovery of one special macronutrient.

It may have been our extraordinary ability to combine:

• Ecological knowledge
• Memory
• Cooperation
• Tools
• Food processing
• Hunting
• Gathering
• Cooking
• Sharing

to obtain energy from an expanding range of environments.

The brain then became part of that feedback system.

A larger brain helped humans acquire difficult foods.

Difficult foods helped pay for the larger brain.

Diet and cognition evolved together.

The Most Accurate Verdict

The 2026 Science paper provides a compelling new argument that dietary sugars and later starches were important contributors to the energetic foundations of human brain evolution. It models the rising glucose demands produced as hominin brains increased dramatically in size and argues that fruit, honey and other naturally sweet foods probably supplied substantial energy long before cooking made starch-rich plants easier to exploit.

The research does not show that:

• Sugar alone caused intelligence.
• Meat was unimportant.
• All humans historically followed one high-carbohydrate diet.
• Refined sugar is healthy.
• Everyone should abandon low-carbohydrate diets.
• Modern honey or sweets can be consumed without limit.

What it does show is that the conventional picture of human evolution deserves a broader nutritional lens.

Our enormous brains required energy.

Glucose was part of that requirement.

For millions of years, carbohydrates helped provide it.

The strange irony is that a nutrient category frequently blamed for modern nutritional problems may also have helped make possible the organ we use to argue about nutrition in the first place.

Frequently Asked Questions

Did a 2026 Science study really say sugar helped human brains evolve?

Yes. Science published A central role for dietary sugars in human evolution on August 6, 2026. The authors argue that glucose supplied by naturally sweet foods and later starches was an important part of the energy system supporting human brain evolution.

Who conducted the study?

The paper was authored by Jennie Brand-Miller, Karen Hardy, David Raubenheimer and Les Copeland, with researchers affiliated primarily with the University of Sydney and University of Glasgow.

Is this an experimental study?

No. It is an analytical synthesis and evolutionary model drawing on existing evidence from metabolism, physiology, primate diets, fossils, dental evidence, archaeology, genetics and food composition.

Did human brains really grow from 300 to 1,500 grams?

Those are approximately the endpoints used in the authors’ evolutionary model, from small-brained early hominins to the modern-human stage.

Did sugar make humans intelligent?

That is too strong. The study argues that carbohydrate-derived glucose helped meet the energetic requirements of enlarging brains. It does not prove sugar alone caused increased intelligence.

Does the human brain need glucose?

The brain normally relies heavily on glucose for energy, although metabolism can adapt during fasting or very-low-carbohydrate intake and use more ketone bodies.

Why could fruit have mattered to early humans?

Fruit supplied readily accessible carbohydrates along with water, fiber and micronutrients, making it a valuable energy source before widespread cooking expanded access to digestible starch.

How much energy may have come from natural sugars?

The study’s modeling, as summarized by Nautilus, suggests natural sugars from foods such as fruit and honey may have provided roughly 20% to 35% of dietary energy across important parts of hominin evolution.

Why do some reports say early ancestors got more than 65% of energy from fruit?

Those numbers refer to different things. The earliest chimpanzee-like dietary stage was modeled as strongly fruit based, with more than two-thirds of energy potentially coming from fruit. That does not mean more than two-thirds of calories consisted of pure sugar.

Did early humans eat honey?

Evidence and observations of primate and hunter-gatherer behavior make honey a plausible valuable resource, and the new paper treats it as an important potential source of concentrated natural sugars.

Does that mean honey is healthy in unlimited amounts?

No. WHO classifies sugars in honey as free sugars and recommends limiting total free-sugar consumption.

Was meat still important in human evolution?

Yes. The authors explicitly say animal foods were important and view meat and carbohydrate-rich plant foods as complementary parts of the evolutionary story.

Did meat make the human brain bigger?

Increased animal-food consumption is one important hypothesis for supporting larger brains because animal foods provide concentrated energy, protein, fat and micronutrients. The new research argues that glucose-rich plant foods should be included alongside that story rather than replacing it.

Did Paleo humans eat mostly meat?

There was no single Paleolithic diet. Human and prehuman diets varied enormously by species, geography, climate and available food resources.

Does this prove the Paleo diet is wrong?

It challenges highly meat-centric versions that portray ancestral carbohydrate consumption as trivial. It does not test modern Paleo diets clinically.

Did humans eat carbohydrates before agriculture?

Yes. Fruit, honey, roots, tubers and other plant foods provided carbohydrates long before agriculture or domesticated grains.

Did humans eat starch before farming?

Yes. Underground storage organs and other wild plant foods contain starch. Cooking later made many of these resources easier to digest efficiently.

Did cooking make carbohydrates more useful?

Cooking can substantially increase accessibility of starch by changing its physical structure, which allows digestive enzymes to process it more efficiently. The new evolutionary model treats cooked starch as increasingly important later in human evolution.

When did humans begin cooking?

The exact timing remains debated. Evidence for fire extends far back in prehistory, but proving habitual cooking is more difficult, and some substantial brain expansion appears to precede unequivocal evidence of regular cooking.

Does the study prove fire caused another leap in brain evolution?

No. It proposes that cooking expanded access to starch-derived glucose, but the evolution of human brain size cannot be attributed to one event.

Why are pregnant women important to this hypothesis?

Pregnancy adds glucose demands from the fetus and placenta, while lactation adds further metabolic requirements. The researchers argue that reproductive energy needs must be considered when reconstructing successful ancestral diets.

Why do children like sweet foods?

Humans appear to have an innate preference for sweetness. The researchers suggest this may partly reflect the unusually high energetic demands of the developing brain.

Does a child’s brain consume two-thirds of all daily calories?

No. That is a common misstatement. Peak childhood brain metabolism has been estimated at approximately 66% of resting metabolic rate, not two-thirds of total food energy. Another analysis places it around 43% of daily energy requirements at the peak.

Are carbohydrates essential nutrients?

Specific dietary carbohydrates are not “essential” in the same technical sense as essential amino acids or essential fatty acids because humans can synthesize glucose. That does not mean carbohydrate-rich foods were unimportant in human evolution or are nutritionally worthless.

Can humans survive without eating many carbohydrates?

Yes. Human metabolism can adapt to carbohydrate restriction by producing glucose internally and increasing the use of ketone bodies. That metabolic flexibility does not tell us what diets supported millions of years of hominin evolution.

Does this study disprove ketogenic diets?

No. It is an evolutionary analysis, not a clinical comparison of ketogenic versus higher-carbohydrate diets.

Should everyone eat a high-carbohydrate diet?

The study does not establish one ideal macronutrient ratio for every modern person.

What carbohydrates does WHO recommend?

WHO recommends obtaining carbohydrates primarily from whole grains, vegetables, fruits and pulses such as beans, lentils, chickpeas and peas.

How much carbohydrate does WHO recommend?

WHO’s current healthy-diet guidance notes that carbohydrate intake can vary and that, for most people, unrefined carbohydrate foods can make up a substantial portion of energy intake. Its strongest emphasis is on the quality and food source of carbohydrate.

Are refined sugars the same as fruit carbohydrates?

No. Whole fruit packages sugars within water, fiber, micronutrients and intact plant structure. Refined sugary foods can deliver concentrated energy with much less of that nutritional matrix.

What are free sugars?

WHO defines free sugars as added monosaccharides and disaccharides plus sugars naturally occurring in honey, syrups, fruit juices and fruit-juice concentrates.

How much free sugar should people consume?

WHO recommends limiting free sugars to less than 10% of total daily energy, with further reduction to 5% or less potentially providing additional health benefits.

Does the study mean fruit is better than meat?

No. Fruit and animal foods provide different nutrients. Human evolution likely benefited from dietary diversity rather than one universally superior food.

Why might researchers have underestimated plant foods?

Plant foods often leave less obvious archaeological evidence than animal bones and stone-tool butchery marks. This can make prehistoric plant consumption harder to reconstruct directly.

Is the new theory accepted by every anthropologist?

No scientific model of four million years of diet is universally settled. Researchers commenting on the study agree carbohydrates deserve attention but debate issues such as the degree of previous “meat bias,” reconstruction assumptions and the timing of cooking.

What is the biggest limitation of the study?

It reconstructs ancient diets through modeling and multiple indirect lines of evidence. Exact diets, food availability and cooking behavior cannot be known perfectly millions of years later.

Does the paper overturn everything scientists thought about human evolution?

No. It extends and reframes existing research by emphasizing glucose and natural sugars alongside already recognized roles for meat, food processing and diverse foraging strategies.

What is the simplest takeaway?

Human brains are metabolically expensive, and carbohydrate-rich foods probably helped provide the energy required to support their evolution.

Should we stop fearing carbohydrates?

For most people, treating all carbohydrates as inherently unhealthy is not supported by modern dietary guidance. The more useful distinction is between nutritious carbohydrate-rich foods—such as fruits, vegetables, whole grains and pulses—and diets dominated by refined carbohydrates and excessive free sugars.

What does this study really change?

It changes the evolutionary story from:

“Meat gave us big brains.”

to something closer to:

“Human brain evolution depended on an increasingly sophisticated omnivorous diet in which animal foods, natural sugars and later starches all helped satisfy extraordinary energetic demands.”

That may be less dramatic than declaring one nutrient responsible for humanity.

It is also much closer to the wonderfully complicated way evolution actually works.