Long before there were bakeries, sweet shops, or a jar of honey on the shelf, our ancestors were already chasing something sweet — and that instinct may have quietly built the very brain we now use to crave it.

• A 2026 study in the journal Science found that natural sugars, not meat, may have driven much of human brain growth over four million years
• Human brain size grew from about 300 grams to roughly 1,500 grams, and glucose is the brain's main fuel
• Early humans likely met that glucose need through ripe fruit and honey, long before cooking made starchy foods easy to digest
• Grains entered the human diet far later, with the earliest seed-grinding evidence dating back only about 65,000 years
• The findings suggest our love of sweetness is an ancient survival trait, though the researchers are clear that whole fruit is very different from refined sugar

Yes — according to a 2026 study published in the journal Science by researchers at the University of Sydney and the University of Glasgow, natural sugars from fruit and honey likely played a bigger role in growing the human brain than meat did. Led by nutrition professor Jennie Brand-Miller, the research modelled the glucose needs of human ancestors across four million years of evolution. As brain size grew from around 300 grams to about 1,500 grams in modern humans, the demand for glucose — the brain's primary fuel — grew right along with it. The study suggests our ancestors met much of that demand through naturally sweet foods, well before grains or cooked starches were part of daily life.

Why the Brain Needed So Much Glucose

The human brain is unusually large for our body size, and it runs almost entirely on glucose. But the brain was not the only organ competing for it. The researchers calculated what they called "obligatory glucose demand" — the sugar needed by the brain, red blood cells, kidneys, and reproductive tissues, including the placenta and mammary glands during pregnancy and breastfeeding. Women who were pregnant or nursing needed noticeably more glucose than other adults, since building a fetus, producing milk, and forming new brain tissue all draw on the same fuel supply. As hominin brains grew larger across six evolutionary stages, from early ancestors similar to "Lucy" through to Homo erectus, this baseline glucose requirement kept climbing.

Fruit and Honey Before Grains

Here is the part that reframes the usual story of human evolution. Raw starch does not release much glucose on its own — it needs cooking to become digestible. So before fire and cooking were widespread, our ancestors could not have relied on grains or raw tubers for their sugar needs. Instead, the study points to ripe fruit and honey as likely staples, supplying energy long before farming existed. Archaeological evidence backs this up: the earliest known seed-grinding stones, used to make flour, date back only around 65,000 years. For millions of years before that, sweetness in nature — not bread or cereal — was doing the heavy lifting for our growing brains.

What This Means for How You Eat Today

None of this is a case for eating more sugar. It is a case for eating the right kind. The researchers were careful to point out that sugars found in nature come bundled with fiber, vitamins, minerals, and other compounds that slow digestion and add nutrition — very different from refined or added sugars eaten on their own. Global health guidance reflects this same distinction: the World Health Organization's guideline on free sugars intake recommends limiting added and refined sugars, while whole fruit is not included in that caution. It is worth noticing that many traditional Indian sweets already followed this instinct long before the science caught up — using dates, jaggery, and dried fruit instead of refined sugar. Our own Dry Fruit Ladoo, made with dates, figs, and raisins and no refined sugar, leans on that same idea — energy the way nature originally packaged it.

If you are looking to satisfy a sweet craving the way our ancestors might have, reaching for a naturally sweetened bite like our Dry Fruit Ladoo is a small, simple way to do it.

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Frequently Asked Questions

1. Did early humans eat more sugar than meat?

Not exactly — meat, fat, and protein remained important parts of the human diet. But researchers found that fruit and honey supplied much of the glucose the growing brain needed, especially before cooking made starchy grains and tubers digestible, showing carbohydrates played a bigger evolutionary role than previously recognized.

2. Why does the human brain need so much glucose?

Glucose is the brain's main energy source and is also required by red blood cells, kidneys, and reproductive tissues like the placenta during pregnancy. As the human brain grew from around 300 grams to 1,500 grams over millions of years, the body's baseline glucose demand rose sharply alongside it.

3. Is fruit sugar the same as refined sugar?

No. Natural sugars in fruit and honey come packaged with fiber, vitamins, minerals, and other beneficial compounds that slow digestion and support health. Refined or added sugars lack this packaging, which is why global nutrition guidelines recommend limiting free sugars rather than whole fruit.

4. When did grains become part of the human diet?

Much later than fruit. Archaeological evidence shows the earliest seed-grinding stones date back around 65,000 years, while fruit-based sugars are believed to have supported human energy needs for millions of years before that, well before farming or bread-making existed.