TV review: Meet the Izzards, BBC1

People Like Us, BBC3

"I don't know where I'm going," Eddie Izzard confesses as he digs for tubers in Namibia's Kalahari desert.

He succeeds in gathering the roots, quipping that his painted "nails [are] still intact". It's one of the diminutive funnyman's droller asides in Meet the Izzards, a portentous documentary that opens with narrator David Morrissey proclaiming: "Eddie Izzard. Actor. Comedian. Transvestite. And marathon runner extraordinaire... is about to embark on a remarkable journey using his own DNA as the road map."

Yet another genealogy programme, then, but this time going back 10,000 generations instead of 200 years and taking in a host of no-expenses-spared, exotic locations. This is "epic" and "momentous", Morrissey booms. THIS IS IMPORTANT.

Like all TV travelogues, your enjoyment of it very much depends on your travel companion and inscrutable Izzard, with his Malcolm X-style goatee, is certainly game: he digs in the dirt, gleefully makes a fire, collects berries and dances like a sozzled uncle taking to the dance floor at a posh wedding. But do we actually give a hoot about his ancient ancestors? Not really.

The 51-year-old Izzard is sent on his way by Edinburgh University's Dr Jim Wilson, a groovy geneticist (he sports dark shades on his head; his online profile has him at the wheel of a speedboat) who pops up intermittently with boffin gumpf such as "Eddie's next key marker gave birth to the L3 branch... but what's really interesting is the next marker after that, which produced the N branch." Right. Thankfully, he's cut short by more pretty shots of Africa and remote locations such as Djibouti's Bab-el- Mandeb Strait, which is "saltier than the Dead Sea". It provides Izzard with an opportunity to look wistfully out at a huge expanse of water – an obligatory shot in ancestry shows. Wistfulness is key, too.

Due to political unrest Izzard can't visit Yemen, where he was born, so the narrow-eyed comic makes his way to Turkey's Black Sea coast instead to discover where his "blue eyes came from". Cue awkward chats with busy farmers and close-ups of goats being milked. He also stays in the hotel where his parents honeymooned: Izzard's mother died when he was six; his father is a sweet fellow with an immaculately kept front garden. Izzard appears too durable and impenetrable a character to give us easy tears, another key component to this kind of documentary's success. The emotional payoff is absent here.

Then it's Pompeii and by then interest drifts. Even Izzard's vim seems to have receded until he enters "a house of sex" and views smutty scenes on the wall. Up pops Wilson again to boldly claim "that we're getting to a really exciting stage of the genetic journey", while staring at some unfathomable stats. Izzard heads for Denmark, then Northamptonshire. It's not that exciting.

There are more (dubious) thrills to be had from BBC3's less ambitious but more visceral People Like Us, a look at the people of Harpurhey, Manchester, one of Britain's most disadvantaged inner-city neighbourhoods. "There's water that comes through my fire alarm," explains unemployed chef Pidge, a 21-year-old who's been arrested seven times in eight weeks since moving into his leaky hovel, owned by unnerving landlord Nik (think of a furtive Mark Heap on Chris Morris's Jam) who explains that locals "will steal the snot out of your nose".

More endearing are gay pals Arroll and Patrick, who are getting a facial ("You look like Dale Winton on crack") before their first summer holiday in Kavos ("Chavos") together and make observations such as "Kate Middleton's got nice eyebrows". Most amiable of all is copper Jim Evans, who remains remarkably sanguine despite policing one of the "highest crime areas in Manchester" and having to haul miscreants out of Asda. Horribly compelling, but Lord alone knows what our ancestors (or Dr Jim Wilson) would make of it all.