Gochos The Greek wrote:How are they fake?
How? A bit of reading shows that they were hand crafted beginning in the 19th century with the intention of deceiving people into believing they are pre-Colombian in origin for the motive of profit. That's a good working definition of a hoax. They're one thing deliberately being passed of as something else, something far more fantastic, for the purpose of aggrandising and enriching the supposed finder.
The problem is that no records or images of such skulls appear anywhere in recovered Mesoamerican cultural artefacts. That's a big flaw in the premise to the hoax. In fact, rather tellingly, the first mention and speculation about their origins is by their 19th century finders. They first come to light being sold by the French antiquities dealer Eugène Boban in Mexico City between 1860 and 1880. It's as if they simply didn't exist before that time, which metaphorically places the hoaxers fingerprints all over these otherwise stunning pieces of work.
Studies undertaken in the past 15 years or so (including one published this year that used electron microscopy and X-ray crystallography) have shown conclusively that the tooling on the skulls was made using powered rotary tools available from the 19th century onwards, and using a synthetic abrasive called carborundum which was only available after 1890. One skull is now dated to ~1950. Also, the structure and composition of the crystal used in the skulls studied identifies it as Brazilian and European in origin. It couldn't be from the area it's supposed to be from because geological conditions don't create quartz there. Could the Mesoamericans have travelled to get it? No. There's no evidence of their civilisations in Europe or Brazil even though these civilisations are very "noisy" in the physical record. So the hoaxers began from a flawed premise, which is bad hoaxmanship.
All this is a salutary lesson for anyone creating a genuinely believable persona: assume nothing because assumption, like a high fat diet, is like a psychotic homing pigeon. Sooner or later, it'll hunt you down and kill you

Why am I not in the pub? It's Saturday afternoon. I demand to have some booze!