Last Night's Television: Who Do You Think You Are?, BBC1<br />The Cell, BBC4

Science hasn't been in the best of shape on British television recently. Equinox seems to have disappeared into some broadcasting black hole, Horizon has been steadily regressing into second childhood and mainstream offerings – such as Bang Goes the Theory – appear to be pitched at a hyperactive seven-year-old out of his skull on SunnyD. There are sporadic efflorescences of the serious on BBC2, but if you want something sustained and detailed your last best hope is BBC4, a little cranny in the rock that sustains some flourishing micro-cultures of straightforward instruction. And even here there are signs that the evolutionary pressures are having their effect. In The Cell, for example, Dr Adam Rutherford referred to Anthony van Leeuwenhoek as "a lens geek", to Robert Hooke as "the go-to guy when you had very small things to investigate", and concluded a little aside on Robert Brown's unique double contribution to physics and biology with the exclamation "Respect!", possibly the least convincing attempt to sound "street" since Richard Madeley channelled Ali G on the This Morning sofa.

I think we can forgive Dr Rutherford these brief lapses of taste because The Cell is refreshingly gimmick free. This is a sturdy bit of science history, neatly crafted to introduce one of the biggest ideas in biology to a general audience. And it's a story that, in its early stages at least, belongs to the brilliant amateurs – men like Van Leeuwenhoek himself, who worked by day as a linen merchant and used his spare time to grind the best microscopes in the world. Leeuwenhoek's lenses were so good, in fact, that his scientific contemporaries weren't always convinced that he wasn't making things up. Gratifyingly, rather than dismissing the findings of Johnny Foreigner, Hooke put forward a more open-minded theory as to why he couldn't replicate Leeuwenhoek's observations of protozoa: "Either my microscope was not so good as the one he made use of or... Holland might be more proper for the production of such little creatures." In the end, he improved his equipment and saw the same things. Rather than being mocked Van Leeuwenhoek ended up as an honoured Member of the Royal Society.

The Royal Society's motto – "Nullius in Verba" – roughly translates as "Take Nobody's Word for It", a sentiment that can't always be adhered to when watching television. I'm just going to have to take it on trust that Dr Rutherford supplied his own semen sample in order to replicate one of Leeuwenhoek's early ventures in microscopy and that what we saw on screen genuinely were "tiny little Adams". I have no way either to verify whether he correctly followed Jean Baptiste van Helmont's procedure for spontaneously generating mice from human sweat and wheat, an enterprise designed to illustrate the medieval guesswork from which modern biology first had to free itself before developing cell theory. But he seemed a reliable type and the story he told – the realisation that all life on earth shared a cellular kinship – satisfyingly derived nearly all of its thrills from the ideas it contained, rather than the style in which they were tricked out.

Kim Cattrall was the celebrity clambering through her family tree in Who Do You Think You Are? this week, and in particular reconstructing one sawn-off branch, following up the mystery of her grandfather's abandonment of his wife and three daughters – now Cattrall's mother and aunts – leaving them in desperate poverty. George, the bolter, was eventually discovered to have married again bigamously in County Durham, where he brought up a family of four children before emigrating to Australia, where he lived his life out in modest prosperity. His daughters, confronted with pictures of the happy childhood that they'd effectively had stolen from them mouthed abuse under their breath and wept – three old ladies suddenly eight years old again. "I'm hoping to find something in his face that is about regret or remorse," Cattrall had said, shortly before she was shown the first photographs she'd ever seen of her grandfather. Fat chance, though some kind of retribution had trickled down the generations. Out there in Australia, presumably, four people have just had their childhood memories of dad completely upended, despite the fact that they never signed up for the exhumation of family secrets. The sins of the fathers indeed.