At last, science tells us why buses always show up in threes

Why do you never see baby pigeons when the adult birds are so common? Why do insects never get fat? And why do buses always seem to arrive in threes?

Why do you never see baby pigeons when the adult birds are so common? Why do insects never get fat? And why do buses always seem to arrive in threes?

These long-standing riddles are among the 10 questions that most trouble members of the British public, according to research by the Discovery television channel.

Discovery supplied some of the answers yesterday, including the explanation that young pigeons stay in their nests until they are fully feathered, by which time they are almost indistinguishable from adults.

The secret of insects' slenderness is that their skeleton is external, not internal, which dictates their dimensions. Rather than getting fatter, a greedy fly will eventually burst.

The regular gripe of commuters – that they wait hours for a bus and then three come along at once – may have some truth in it. According to Discovery, if a large number of passengers cluster at one stop, the bus that picks them up is delayed as they pile on board. As the second bus catches up, there is less time for a queue to form by the time it comes to the stop, so it gains even more ground. On a long route, a third bus will catch up as well.

The question of why men have nipples is also answered by the channel. The human embryo develops mammary tissue before deciding whether to be male or female. In a male foetus, the "milk ridges" regress and leave the nipples behind.

Then there is the custom of clinking glasses and saying cheers. This is said to date back to the ancient Greek habit of poisoning one's enemies. To prove wine was safe, a host would pour some of his guest's wine into his own cup and drink it first. But if the guest had confidence in his host, he would merely touch his cup against the other's. The "clink" was a sign of trust.

And finally: why are things always found in the last place we look? One does not need scientific genius to unravel this one. Once we have found the object of our search, we stop looking.