Its a cool animation but its not belived to be complete..
Most importantly is that the history of the arctic and the northern hemisphere is much older then what is believed today. There were humans in the arctic during the whole ice age. Furthermore we have just discovered that there was ice free forested refuges in Scandinavia during the ice age too.
They have discovered that both Scandinavia and Siberia was warmer then it is today during the ice age, this is a major puzzle that presents questions that modern science has not yet understood.
http://www.newsinenglish.no/2012/03/02/norwegian-trees-survived-ice-age/
Also that settlements on the arctic ocean is far older then what we have thought..
http://www.archaeology.org/0403/newsbriefs/siberia.html
on the Yana River in northeastern Siberia, archaeologists have discovered the oldest known Ice Age settlement north of the Arctic Circle. Carbon-dated to about 30,000 years ago, it is twice the age of the previously known oldest settlement
Several new theories have been presented to explain how these things are possible, but there has not been a consensus on any of the new theories yet. Its quite a puzzle since Scandinavia is believed to have been covered by a several kilometer thick inland ice just like Greenland is today, this completely excludes the possibility of pine trees growing there.
... regarding what you are saying about the development of automatic cannabis, i think that it sounds reasonable that nature can move seeds around quicker then man. However, man could be capable of cultivating strains in areas where tehy dont necessarily grow wild. So man could be contributing to the development of certain traits.
But considering that we know that there has been warm climatic refuges several places in the arctic regions at several times in history, its entirely possible that the dwarf autos developed as a result of natural selection somewhere in a northern latitude during one of these warm periods.