SAD LOVE QUOTES: Life expectancy: Grandparents were a rare breed until 30,000 years ago

Wednesday, July 20, 2011

Life expectancy: Grandparents were a rare breed until 30,000 years ago

Last updated at 3:29 PM on 20th July 2011

Grandparents are a relatively new phenomenon, researchers said today.

Until around 30,000 years ago, mankind's ancestors had lifespans that were too short for three generations to live side-by-side, according to a study.

Simply, most people died before they were old enough to have grandchildren.

Scientists said their findings show that once life expectancy began to grow, populations expanded and societies started to thrive.

When grey hair was rare: The advance in life expectancy 30,000 years ago led to grandparents and helped early human societies to expand

It is even possible that early humans' longer lifespans may have been the key factor which allowed them to establish their superiority over competitors like Neanderthals.

A long-running research project, studying the fossils of proto-humans stretching back three million years, reported some of its findings in the magazine Scientific American.

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.

The study, which involves fossil remains from 768 individuals, has been calculating the ratio of older to younger adults in ancient human societies down the millennia.

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.

Early man: The descendants of the first humans to leave Africa thousands of years ago shrank to little more than 1,000.

Early man: Until relatively recently, very few humans lived long enough to have grandchildren

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.

Scientists have concluded that 'adult survivorship soared very late in human evolution', but have so far been unable to explain the phenomenon.

But what is clear is that the longer lifespans brought huge advantages to early human society.

Not only did grandparents increase the 'economic and social resources' of a group, they also passed on 'cultural knowledge', such as traditional hunting techniques, to their descendants.

Eventually, according to the magazine article, 'Longevity became a prerequisite for the unique and complex behaviours that signal modernity.

'These innovations in turn promoted the importance and survivorship of older adults, which led to the population expansions that had such profound cultural and genetic effects on our predecessors.'

The article concluded that early humans were 'older and wiser' than their rivals, which allowed them to out-compete and eventually exterminate them.

These new findings may explain how the human population recovered after being reduced to no more than a few thousand, as reported earlier this week.

A recent study claimed that the group which went on to populate Europe and Asia numbered only 1,200 people at one point.

However, it may be that the advances in longevity promoted rapid population growth which allowed humanity to re-establish itself.