The factors that decide health and longevity are mostly genetically determined. So the medical research last week that recommended a strong handshake got an enthusiastic airing. But are handshakes an expression of physiology or of character?
A firm handshake might be associated with status, wealth and a more muscular and self-confident view of the world. By contrast, a drippy grip can convey timidity, defeatism and low self-esteem.
I remember reading a medical survey that linked women who had undergone cosmetic surgery to premature or unnatural ends. Did surgery cause death, or was the type of woman who chose surgery more metropolitan, flightier and thus generally higher risk?
The illustrations in Tony Blair's autobiography are quite handshake-based, because the gesture denotes power, purpose and public relationships. His favourite is the strong clasp, with thumbs stretched to the wrist, as practised on his buddy President Clinton. The hands are kept low, almost at groin level. It is quite unlike the swift outstretched handshake that leaders use when they want somebody out of the way.
Blair includes a photograph of himself shaking hands with Bertie Ahern after the Good Friday agreement, and none of him shaking hands with Gerry Adams. He does not show off the clenched fist handshake exchanged with Colonel Gaddafi and he omits whole sequences of jolly handshakes with President Bush.
In his book he also broke protocol by revealing his conversation with the Queen. Their private conversation turns out to be identical to the fictionalised account in Peter Morgan's film The Queen. Unsurprisingly, Tony Blair does not grip the Queen's hand to his groin. He approaches the monarch gingerly, holding her fingers rather than wrist.
This raises the question of what sort of handshake a woman should offer. It is all very well for medical research to recommend the manly Don Draper clutch. What does that mean for women who do not play rugby for England? How can they express authority without rippling strength? The Queen wears dignified white gloves, but these would not work for most of us in the workplace.
Even the magnificently self-confident American Secretary of State Hillary Clinton can find her hand vanishing inside a greater male grip. Barack Obama practically squeezed her to death during a pre-election television performance.
On the Continent, there is a further threat to women that their outstretched hand will be kissed. Women need to be firm and above all quick. We have no training in male tricks such as slapping one's spare hand over the handshake like an oyster shell, or gripping the wrist of the hand that we shake.
It is more complicated for teenagers, whose handshakes demand intricate choreography. Handshakes are also slaps and fist bumps and high fives. YouTube offers several guides to cool handshakes. They are as tribal as the freemasons'.
Maybe it is not muscular ability that guarantees longevity, but something else. Competitive instinct and will. The firm handshake contains a Darwinian element. Who grips strongest, wins. It was Tony Blair's need to dominate that took him into politics. And now the world stage offers him 1,000 handshakes. No wonder he is looking so youthful.
Sarah Sands is deputy editor of the London Evening Standard