should you let your dog sleep on your bed?

Do not let your dog sleep on the bed.
Advice well known to all dog owners.
Supposedly it is all about leadership power within the pack. Letting your dog sleep at the same level as you is said to be signaling an equal position in the pack hierarchy.

And for a short time I enjoyed ranking as alpha male status in the bedroom domain. That was, until one cold winter night when Kelly was away and Smudge was still a pup, I felt sorry for the little guy and lifted him up onto the bed.

He embraced his new-found promotion by ecstatically stretching out onto his back, splaying his legs to occupy maximum bed real-estate, and releasing a long ludibrious yawn.
Scrunching over to one side of the bed I had first inkling of my error.

Several hours later, the snoring and farting (his, not mine ), and getting pushed to the outer lip of the mattress put the matter beyond question.

15,000 years ago, somewhere in central Asia, man began interacting very closely with Smudges distant forebearers, the Grey Wolf (Canis Lupus). The long process of this domestication remains controversial but these first ancestors of today’s estimated 400 million dogs (Canis lupus familiaris) were probably used as combination hunting and herding aids, companions, warning alarms, sled pullers and even food sources.
The nature of 15,000 years of close interaction has produced a special close relationship between man and dog that probably does not exist between any other two species.

But as this close bond developed between the species, is there any evidence that we have actually slept with our dogs?

Emily Toffe wrote in an article for Slate magazine:

There is historical evidence that sleeping with pets is not necessarily aberrant behavior. According to The International Encyclopedia of Dogs, the xoloitzquintli, or Mexican hairless, was used in pre-Aztec Mexico as both pet and bed warmer (and dinner—let’s not talk about that here). An account from a 19th-century explorer in Australia, as quoted in The Domestic Dog, describes how Aborigines were so devoted to their dingoes that the dogs were treated as members of the family and allowed to sleep in the hut. (The rock group Three Dog Night takes its name from the supposed Aboriginal practice of judging the coldness of an evening by the number of dogs required to keep warm.)

Ever since that first invitation to join us, Smudge has spent almost every night on our bed. Except for those mid summer heatwaves when he seeks the coolness of the bathroom tiles.
Each evening he follows his well ensconced routine.
Just after 7PM, he gets up form the couch, goes over to his bowl and scoffs down the remainder of his biscuits (which he routinely sets aside for just this snack).
Next, he noisily drinks his fill, and spends a few minutes in a snorting contemplation of each of his soft toys he will choose to bed.
And off he trots. Without so much as a “goodnight guys”.
Later, we will find him asleep, just like a human, under the covers with his little head on one of our pillows and his paw across his green caterpillar. Simply way too cute to assert my evolutionary superiority over.

For Smudge, there is absolutely no issue with nocturnal altitude and hierarchy. He will lose no sleep contemplating issues of family dominance.
For him, its just another Two Human Night.