HORIZON: What Makes Us Human? (BBC2, Wednesday of last week) is a title arresting enough to save me thinking up my customary opening gag designed to attract your attention. Professor Alice Roberts trod again that well-worn documentary topic of what it is that marks us out from our closest living relatives, the apes.

It was well worth watching, because she came up with a couple of new and significant insights. One experiment demonstrated that, at the level of lateral-thinking problem-solving, chimpanzees are more intelligent than humans.

Another test showed that apes, like human children, can quickly learn to co-operate to succeed at a task that rewards them. The unexpected difference was that when the prize was unequally divided between the two partners, the winning ape gleefully scoffed her share, while the child shared her winnings with her unfortunate partner. So much for original sin.

Why are humans born so helpless? Compared with apes, our babies need years of nurture before they can fend for themselves. The accepted explanation is that two competing vital human characteristics force an uneasy compromise: our bigger brains mean that we have larger heads; and our unique upright stance requires our hips to be as narrow as possible.

Add these together, and for women to compete in the race of life, their birth canals must be so restricted that giving birth is extremely painful; and humans are, unfortunately, born at a far earlier stage of their development than other species.

But new research challenges all that. Width of hips makes very little difference to speed of running. Humankind's most unique feature is its complex social interaction, of which language is merely the apex. In other words, remaining solitary in the womb won't work: we have to be surrounded by others while still being formed. We are born at exactly the right moment.

All this was given personal context by the fact that Roberts was pregnant while making the film, and continually referred to the new life growing within her.

A child abandoned by his mother formed the core of Henry, last Monday's episode of Coming Up, Channel 4's admirable series that gives emerging writers and directors a slot to produce a drama. Karen, abandoned by her husband, despairs of being able to care for her toddler. After a day of humiliating failure, she gives in to a wild impulse and leaves him with a well-off stranger, in the hope that he will have a better upbringing.

This drew us into the pain of her life, thwarted not by ogres but by circumstances that no one was able to alter. My only hesitation is that the heroine was too beautiful and well turned out to be entirely believable; but that is no criticism of her acting.

In Burma, My Father and the Forgotten Army (BBC2, Sunday) Griff Rhys Jones focused on Britain's shameful post-war treatment of the West African troops who had achieved "the greatest feat of arms of the Second World War". It was a fine example of a programme that starts off exploring one topic, then is taken over by passion and conscience into another direction.