In the Highlands of Scotland, the carved stones of the pre-Celtic Pictish people of Alba are the legacy of a mighty warrior race who defied and defeated Rome, who slaughtered hordes of invading Angles [Germans], and who quickly sent the invading Viking warriors back home.
By 845 A.D. the migrating Irish Celts had secured the Kingship of Pictish/Celtic Alba (Celtic Scotland). A Celtic Scot, Kenneth, Son of Alpin, son of a Pictish princess ruled over both Picts and Celts.
The Picts were a fiercely independent people, of which little is known today, other than that the Romans feared them. Rome built Hadrians wall in an attempt to stop the Picts attacking their Garrisons. The Picts were also said to be magnificent sailors, equally feared by the Romans.
By the end of the tenth century the Picts had completely and mysteriously disappeared. It is considered one of the greatest mysteries of the Scottish Highlands.
I don't think it is such a mystery... Being such masterful sailors, I think this unique and very different (to the Celts) Pictish ethnic race left the North of Scotland after their defeat and "Mac Alpin's Treason".
Rather than share Scotland with the Pictish Rulling families, the Gael warrior king Mac Alpin [son of Alpin] brutally murdered the families of the seven Pictish ruling households, securing power over Scotland for the "Gael line of Kings".
Climate Change & Turmoil 834 A.D.
I have this theory that "Climate Change" defeated the previously undefeatable Picts. Not just extreme climatic change in Alba/Scotland .. but more widespread climatic changes that affected the Vikings, the Angles, the Romans, the Gaels (Celts), the Gauls and the Normans.
I have this theory, that these cultures were all looking for and fighting over "resources" as well as "land" and "food". That is my theory...
Half Naked Picts & Naked Celtic Warriors
Half naked Picts in the North of Scotland, who took time to completely tattoo their bodies with elaborate designs. Naked Celtic warriors fighting battles against the Romans. Obviously, the climate had to be much warmer than it is now.
I also think that the mysterious Picts were a different ethnic race than the Gaels / migrating Irish Celts. The descriptions of the elaborate full body tattoos makes me think of the Japanese.
I don't think the Picts "disappeared off the face of the Earth"; but that once the seven ruling houses were destroyed .. the Picts sailed off to new lands. Most probably, because the climate was changing rapidly, and it was getting too cold to run around half naked in the Highlands of Scotland.
At the time the Picts were defeated, there was clearly some kind of mass migration/resource chaos taking place across ancient Europe.
Around 834 A.D. to 839 A.D. the Irish Gaels / Celts were on the move migrating in increasing numbers to Scotia - the Scottish Highlands. The Picts were fighting a wave of invading Celts. They were also fighting new waves of Viking hoards as well as Norsemen who conquered the Shetland Isles and the Orkney Isles as they pushed South.
It is clear from the early descriptions of half naked and naked Pictish and Celtic warriors that the Northern climate was a lot warmed than it is today. I think that after 834 A.D. climate temperatures began to radically decline leading to a push from Rome to control greater areas of land and dominate Europe as a move for self-survival.
I also think that the Mayan's had unique and extensive knowledge of these naturally occurring climate cycles, and this is why they became so expert in predicting each new cycle. The Mayans and many original Native Cultures knew about and understood these naturally occurring Earth climatic cycles.
Let's say that the ancient Picts began to experience a much colder climate than the one they were used to. At the time of the Picts, it was getting COLDER .. and today the climate appears to be getting WARMER. We are used to a much cooler climate .. just as the ancient Picts were used to a much warmer climate.
Climate & Civilisations
When climate temperatures alter RAPIDLY civilisations fall and decline as other civilisations rise and grow. Population density alters in relation to adaptability and ethnic / cultural resourcefullness.
For example, white Europeans adapted very well to a cooling climate .. using the advantage to colonise most continents on Planet Earth. As temperatures rise, Europe and America are going into decline in a similar way to the Picts and later the Gaels / Celts and the Gauls.
To say: We have to do something to stop changes in the Earth's climate .. is like going to the shore of the oceans and commanding the waves to stop.
The Earth's climate has been changing for millions of years!