Television Review

AT THE beginning of The Secret Life of Twins (BBC1), Robert Winston rated twins "amongst... the most valuable people in the world, because they help us understand what makes us who we are". This seemed overstated, but twins do encourage that sort of thing - they bring out the part of us that wants life bigger, gorier and freakier.

This programme had plenty to satisfy those appetites: the customary stories of twins masquerading as each other, twins brought up continents apart who both had wives called Fiona and bluebird tattoos... David Teplica, a plastic surgeon and photographer who specialises in snapping identical twins, showed how they replicate one another in minute detail, down to individual eyebrow hairs - then explained how, years after he began this project, he discovered he was the surviving half of a pair. Whooo, spooky. At one point, Winston speculated that the special "bond" between twins could be traced back to their time in the womb. The idea was pleasingly undercut by an illustrative film of embryonic twins headbutting each other.

But all this boggling went along with some genuine information. Even among identical twins, there are different varieties. If embryos split within 10 days of conception, you get carbon copies; if it happens between 10 and 13 days, you get mirror images, one right-handed, one left-handed. If they split after that, they cannot fully separate, and you get Siamese twins.

The cameras followed Lori and Reba Schappell, 37-year-old twins from Philadelphia who are joined at the head. They share a great deal of brain tissue, but not thoughts or sensations. Indeed, they work hard to maintain separate lives, showering separately, having different hairstyles (Lori's is short and dark, Reba's is long and dyed red). Lori said she is something of a drifter, while the more motivated Reba has managed to carve a career as a country and western singer. The awkwardness of their lives is compounded by the fact that Reba is paralysed from the waist down by spina bifida, and has to be pushed around on a tall, wheeled stool. Still, they seemed to get on pretty well, as Reba said: "In a situation like this, this is where you really learn to compromise."

Their experience was almost too strange to marvel at, let alone take as an occasion for moralising. Still, there was something chastening in seeing people survive and stay individuals in the face of such odds.

Sharks - the Truth (BBC1) set out to show that these predators are not mindless killing machines: on the contrary, they are highly intelligent ones. There was some balancing footage of sharks courting, giving birth and filtering plankton through their gills; but mostly it was the usual parade of them biting seals in half, gulping down baby albatrosses and scoffing seal pups whole ("No more than a snack," commented David Attenborough, "but packed with nutrients"). The film also explained how to recognise hostile body language in a great white shark (large pectoral fins point downwards, flashing white patch at base). As a rule of thumb, though, if you're close enough to spot this, the information isn't going to do you any good.