They smoke, drink, and are overweight. They are nearly 100 years old - and Jewish.

This week an Israeli-born academic revealed the secret: it's in their genes.

In London this week to speak to the Royal Academy, Professor Nir Barzilai, director of the Institute of Ageing in New York, discussed his pioneering 12-year study of 500 Ashkenazi Jews aged between 95 and an astonishing 112 years old.

While it was desirable for people to live a healthier lifestyle, it would not guarantee they would live to a ripe old age - and many of those in the study smoked, were overweight or had high cholesterol.

So how was it that the New York Jews had reached such great ages?

It seems to be genetic programming. Professor Barzilai said that Jews had "a very long history where we were persecuted and killed. We became isolated and there was inbreeding, with cousins marrying cousins. In fact, we are all like cousins".

But he was anxious to dispel the suggestion that Jews live longer. He said: "Our assumption is that they live much the same as everyone else, with the same incidence of centenarians as the rest of the population.

"This is about the achievements of the Jews, of the abilities of their genome to solve medical questions because of their inbreeding and lack of variability."