Melvyn Bragg rounded the numbers up. The Origin of Species had been published "nearly 140 years ago", he said, introducing a round table discussion about the disputed border between social studies and evolutionary theory. As anniversaries go that wasn't particularly convincing, but the refreshing truth is that there was no commemorational alibi for BBC2's weekend of programmes about evolution, no calendrical imperative to address it now rather than in another eleven years time, when "the most powerful idea ever to occur to the human mind" will celebrate the 150th birthday of its formal publication. What had provoked this intriguing miscellany was the current vigour of the idea itself - still hot to the touch despite the many years which it has had to cool and congeal into a commonplace truth. Ordinary people can now talk about themselves as "human animals" without a flicker of existential dismay - as a woman happened to on Friday, in a programme about working from home - but that does not mean that the theory of natural selection (Darwin's true stroke of genius) has lost its effervescent energy, the sense of vast implications copiously pouring from a modest container. 139 years on, the bust of Darwin shows signs of displacing those of Freud and Marx in very different disciplines - a fact which raises almost as much alarm now as our primate ancestry did in Victorian days.

The best of the programmes were those that addressed this directly, rather than treating evolution as a simple inherited truth. In The Darwin Debate Melvyn Bragg chaired a discussion of the limits of evolution's explanatory power, an encounter which combined good manners with the necessary amount of argumentative friction. Stephen Pinker championed the fundamentalists, those who are pushing Darwinian ideas into hitherto cordoned areas of human experience, while Steve Jones and Jonathan Miller tried to hold some ground for culture. What fascinated here was the sense of man as a creature half emergent from the primal sea of natural selection, indelibly stained by its processes but capable of ignoring its laws.

This was nicely demonstrated when Stephen Pinker trumped a riposte from Steve Jones - how, the latter challenged, can evolution account for the likelihood that, by 2010, around half of mothers will be step-mothers (that is bringing up children that are not their own). It can't replied Pinker, but it might have something to say about why step-parents are many, many times more likely to abuse or even kill their charges. A social choice may cut against the grain of biological instinct. Darwin: The Legacy, David Malone's clear and often beautiful primer in the schisms of evolutionary theology, offered a similar sense of understanding in the making, of scholars struggling with a new intellectual territory which had still not been mapped in its entirety. A weekend can't begin to do justice to the subject but this one should have recruited some more cartographers.

It is a popular misconception that evolution produces perfectly adapted organisms (rather than organisms just that bit better than their rivals). If you needed evidence that this is a fallacy you could hardly improve on the National Lottery Big Ticket (BBC1), with its singularly unflattering representation of homo ignorens. On one level this programme is obviously intended to fill the niche in the BBC broadcast ecosystem left vacant by the extinction of It's a Knockout. On another level it's simply intended to sell more scratch cards for Camelot. It seems to me to drive a coach and horses through the BBC's own guidelines (following the ruts left by the all the others that have already passed that way) but is it any good?

Not quite good enough, I think, even though the size of the final jackpot adds a certain spice to every round. But the fun-park technology is not always very interesting to watch and the attempt to incorporate the good cause alibi into a stadium-type gameshow often rather queasy in its effects. It was also unwise of Anthea Turner's agent to permit the presence of a computer-generated virtual presenter who is much more lifelike than her client. Watching these two animatronics side by side, I could swear I heard the cogs of natural selection tick forward another notch.