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Right of passage.
But now scientists have tracked down the evolutionary origins of kissing,
and it wasn't humans that started it.
I'm Hannah Gelbart.
I'm the host of What in the World, an award-winning daily podcast from the BBC World Service.
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On an average, I drive like 10,000 miles a month.
For a year, it becomes like 120,000 something like that.
It's too much here.
Sukpal Singh sits behind the steering wheel of his truck,
about an hour from Toronto on Canada's east coast.
Here, there are more than a million trucks,
just like his, criss-crossing the country's roads each day.
It can be a tough job, long hours alone, weeks on the road and little time at home.
And more and more, these jobs are being done by Sikh truck drivers, including Sukpal.
Especially whenever I go to some remote areas quite far from the cities,
I know there are a lot of few people that don't know about Sikhism.
This is the documentary from the BBC Wild Service.