Children may be programmed to be fussy about their food, according to a study by British scientists.
Children had similar dislikes of food
They believe being picky about food is an evolutionary trait, designed to protect them from harm.
The scientists from Cancer Research UK based their findings on a study of 564 mothers with young children.
They found children were generally fussy about the same foods - green vegetables, meat and fruit, which historically were the most dangerous.
In early human history, the presence of toxins within many plants made eating fruit and vegetables risky for children, while meat carried a high risk of food poisoning.
Very young children are often happy to put almost anything in their mouths, but by the age of two, many become reluctant to eat foods they have not tasted before.
Such behaviour is known as neophobia and almost all children show it to some degree, although some more so than others.
Lucy Cooke and colleagues at Cancer Research UK's Health Behaviour Unit at University College London carried out a survey to see if children were fussy about certain types of foods.
They questioned each of the mothers on their own and their children's eating habits.
They found neophobic children often consumed very low amounts of green vegetables, meat and fruit, but ate normal amounts of other types of food, such as potatoes, cereals, biscuits, crisps and cakes.
The fussier a child was, the lower their consumption of potentially dangerous foods.
The researchers concluded that neophobia is not a random phenomenon but a carefully directed strategy to avoid particular food types.
"Plant toxins can be very dangerous to children, as could the effects of food poisoning from unrefrigerated meat," said Mrs Cooke.
"So it makes sense that humans may have evolved to be highly suspicious of certain food types as youngsters and only to trust foods they have eaten before."
She said rather than giving children free reign to refuse to eat their greens again, the study findings could help parents.
"If children see their parents eating a particular food before having to face it themselves, they may be reassured that it is unlikely to do them any harm."
Fruit and veg
Dr Lesley Walker, director of cancer information at Cancer Research UK, said parents should encourage children to eat fruit and vegetables.
"Up to a third of cancers could be prevented with improvements in diet, with an increase in fruit and vegetable consumption the top priority.
"Unfortunately, people often form their eating habits very early in life and it can be difficult to persuade them to eat more healthily later on.
"The traditional family meal is becoming a thing of the past, with parents losing their opportunity to demonstrate the tastiness - and the benefit - of vegetables and fruit.
"This intriguing glimpse into the mind of the fussy child suggests that children need active persuasion that their greens really are good for them."
The study is published in the journal Appetite.