It was only 30,000 years ago, when life expectancy began to grow, that grandparents came into being and helped early human societies to expand, researchers have revealed.
Simply put, most of our ancestors died before they were old enough to have grandchildren.
Anthropologist Rachel Caspari said that by examining Neanderthal dental records, her team established that 130,000 years ago, 'no-one survived past 30', which was the age at which they would have become grandparents, reports the Daily Mail.
In the Neanderthal culture there were just four adults past the age of 30 for every 10 young adults. The average life expectancy was between 15 and 30.
However, when researchers turned to the European humans of the early Stone Age, they discovered that the ratio of older to younger adults was 20 to 10, meaning that many people were now living to have grandchildren.
What is clear is that the longer lifespans brought huge advantages to early human society, the researchers say.
They then concluded that early humans were 'older and wiser' than their rivals, which allowed them to out-compete and eventually exterminate them.
The findings have been published in the magazine Scientific American.