Countless generations have relied on grandparents for childcare, emotional support and a helping hand.

Now a theory claims that the older generation may have played a key role in the evolution of mankind.

Fossil experts say the number of grandparents shot up dramatically 30,000 years ago as people started to live longer.

© The Gallery Collection / CorbisSurvival: Grandparents passed on skills such as tool-making and water supplies allowing their offspring to survive for longer
With older people able to look after children, pass on knowledge and share in food gathering, our ancestors were able to spread around the world and develop farming, tools and civilisation.

The theory comes from American anthropologists who charted the life expectancy of our prehistoric ancestors by studying the wear and tear of fossilised teeth.

Although the first modern people evolved at least 100,000 years ago in Africa, grandparents were a rarity for much of prehistory.

© AlamyGran knows best:Good foraging grannies played a significant role in the evolution of homo- sapiens
According to Professor Rachel Caspari, of Central Michigan University, most of our prehistoric ancestors died before the age of 30 as a result of disease, famine, injury or childbirth.

But 30,000 years ago the number of adults seeing their 30th birthday soared. Around the same time our hunter-gatherer ancestors went through a major change in behaviour. Artwork became more sophisticated, tools became more complex and food production shot up.

Professor Caspari believes the two events are linked. 'Living to an older age has profound effects on the population sizes, social interactions and genetics of early modern human groups and may explain why they were more successful than other archaic humans such as the Neanderthals,' she told the magazine Scientific American.

Professor Caspari is unsure why people started living for longer. Some experts have claimed that food-gathering skills improved around the same time.

But the arrival of the grandparenting generation would have given our ancestors a massive boost.

Professor Chris Stringer of the Natural History Museum said older people would have passed on skills including tool-making and knowledge such as the location of food.

They would also help to bind distantly related families together.

'When it came to disputes over access to water holes or to land rich in game, the more elders there were to remember distant relations in other tribes, the easier it would have been to negotiate and share resources,' he told the Observer.