Archive · 20 Aug 2026
Natural Sugars May Have Fueled the Evolution of Bigger Brains
Scientists studied how much sugar energy human bodies needed as brains became bigger.
They looked back over about four million years.
Early humans probably got much of this energy from naturally sweet foods such as fruit and honey.
Raw grains and starchy plants do not release usable glucose very easily.
Cooking later made foods such as wild yams and grains more useful sources of energy.
The brain uses a lot of energy, especially while children are growing.
Pregnancy and breastfeeding also increase the body’s need for glucose.
The researchers say this may help explain why people and children often like sweet foods.
They recommend getting carbohydrates mainly from nutritious foods such as fruit, legumes and whole grains.
A study modeled glucose requirements across four million years of human evolution.
Researchers found naturally sweet foods likely supplied important energy before cooking became widespread.
Human brain size grew from about 300 grams to roughly 1.5 kilograms on average.
Fruit and honey were likely major carbohydrate sources, while cooked tubers and grains became important later.
The researchers say the findings may help explain humans’ instinctive preference for sweet foods.
- Who
- Scientists from the University of Sydney and the University of Glasgow, led by Professor Jennie Brand-Miller with co-author Professor David Raubenheimer.
- What
- A study modeled how glucose needs and food sources may have supported the evolution of larger human brains.
- When
- Across approximately four million years of human evolution; the study was published in Science.
- Where
- The research was conducted jointly by the University of Sydney and the University of Glasgow.
- Why
- To examine how the brain’s growing glucose demands were met and how this may explain humans’ preference for sweet foods.
- Study publication
- Published in Science.
- Evolutionary period modeled
- Approximately four million years.
- Brain-size change
- From an initial estimate of about 300 grams to around 1.5 kilograms in modern humans.
- Model structure
- Researchers examined six distinct evolutionary stages.
- Early carbohydrate sources
- Fruit and honey were likely important for much of human evolution.
- Effect of cooking
- Cooking enabled starches from tubers such as wild yams, and later grains, to contribute more meaningfully.
- Evidence used
- Food composition, fossil isotopes, dental morphology and primate diets.