Show me a Lambert at six months ..

LIFE is full of secrets which, though eternal, fail to be grasped from one generation to the next. Like: nobody tells first-time parents what hard work babies are. The world and its mother-in-law urge young couples to procreate, but do not warn them that once they do life will never be the same again. Social life, home life, career and above all, sex life - all changed, changed utterly.

After this, it comes as a complete surprise to discover what a joy grandchildren are. One of the delights of middle age - along with weekends a deux, holidays out of season, and never having to supervise a teenage party ever again - is the discovery that it is easier to be a good grandparent than it was to be an even passable parent.

Why did it take so long for Darwin's theory to be formulated, when every grandparent can bore for England on evolutionary development and inherited characteristics? The birth of the next generation is living proof of posterity made visible.

My mother used to say: 'The apple never falls very far from the tree.' She meant, children are what they spring from; but when I was a young mother, dragging my protesting toddlers round art galleries and museums to furnish their vulnerable young minds with the best of Western culture, I thought she was wrong. I was quite sure that children are what you make them. Now, with a second-generation perspective, I can see that I was wrong.

It is extraordinary how many newborn babies are the miniature spit and image of some family member. This physical resemblance is matched, as the child grows up, by emerging traits of character, talents and even gesture, which prompt happy argumentative hours of comparison and disagreement and provide an inexhaustible topic of conversation with aged relatives at christenings, who as clan elders love to trump one's new card by citing generations further back.

As a granny three times over, I have come to believe that the newborn child, far from being tabula rasa waiting for the parental imprint, is programmed by genetic inheritance. Parents, teachers, nannies and grannies can lay down a veneer of good manners plus a polish of taste, education and culture, but the extent to which the child accepts these will be modified by its innate qualities.

This should not be taken as a challenge, but a relief. As long as parents are, in Bruno Bettelheim's reassuring phrase, 'good enough', a child's passage towards adulthood will be pretty much what the genes have preordained. There are exceptions - how else do you account for Beethoven? - but by and large people are born and not made.

I would recommend every new parent to write a character sketch of their child at six months - too soon for parental guidance to have made its mark - and again at two or 10 years. The older child usually conforms closely to the original pattern. My 10-year-old daughter wrote a 'report' on her nine-year-old brother which turned up many years later, hidden between the pages of an old cookery book. It was quite uncanny. His good points then are good still; his shortcomings unchanged 20 years on.

I used to think recurring family characteristics were confined to royalty and the aristocracy: the Hapsburg chin, long Windsor upper lip (and philistinism); Cecil intellect, chubby Churchill face and so on. I now believe that this was merely because such families were portrayed and recorded through several generations, thus providing a clear record of their likenesses. But once you sit at the mid-point of a large family (and mine currently spans the ages four to 83) you realise that the same is true of every family.

Peter Townend, who as a social editor for Tatler has been chronicling the British upper classes for half a century, has an encyclopaedic knowledge of their history, marriages and quarterings. He can survey the infants attending a big society wedding or children's party and recognise, from their unformed little features, which family they belong to. The Brudenell or Howard face emerges early.

I now know that the Lambert, Price or Butler face does, too. My partner and I can spend hours discussing his first grandchild, young Oscar (nine months old but already the living spit of his father), happily analysing from which branches of the family tree this particular little apple has fallen.