I've been doing some research, and it turns out that there is undeniable evidence pointing to the fact that the Drysdale sheep evolved from the North American beaver.

Evidence suggests that 300 years ago a farmer named Bill the Farmer was tending to his flock one day when he came across what he later described as a sophisticated hydro-electric power station built across a stream running through his back paddock. This dam was built entirely out of stray drift wood, mud, snot and titanium impregnated reinforced concrete. The power output of this was driving a small woolshed, a sawmill, and a cluster of fast-food outlets, with any surplus siphoned off to the national power grid. This raised several questions in Bill the Farmer's mind such as: Who built this dam? Why on my farm? Should I eat all of my cow-testicle sandwiches now, or wait until lunch time? Can trees feel pain? Do they install smoke detectors in firestations? Bill the Farmer's curiosity piqued when he noticed a band of stray sheep, which he recognised by name to be from a group he lost in a recent unsuccessful coup attempt, to be performing maintenance operations on the dam.

This is one of many such documented occurrences of sheep reverting back to their roots. In another encounter that was carved into ancient sandstone tablets, reports of a mob of sheep attempting to dam up the River Nile, only to be thwarted by angry Egyptians reliant upon the waters for a constant flow of giardia and crypto spiridium.

If you don't believe the insurmountable facts above, try this:

Q. Why do farmers dock the tails off lambs?
A. This is to discourage the natural devolution of the sheep's tail back to a flat paddle shape, built for swimming and slapping mud into piles of sticks.

Q. Why do sheep have wool then?
A. Have you ever slept in a cold, wet dam with a constant flow of river water running over and through it? You'd want to put a jersey on too.

Q. Well how come nobody has made this obvious connection before then?
A. Because everyone in the world is stupid except me - that's why. I hope this has been an enlightening experience for you. I'll try to keep you informed of further flashes of brilliance, as and when they occur.