(go to 1:01:33 in the video).
(see footnotes below)
Many people are familiar with these images of stone heads, called Moai by the locals. Ancient Aliens tells us that nothing is really known about them:
Ancient Aliens: “How in the heck did they make these; where did they come from and how did they move them? Nobody has the answer.”
This isn’t true at all. For instance, we know exactly how they were cut and shaped. Because the construction of the Moai was abandoned abruptly, so there are plenty of examples of Moai in various stages of development. 
Also the stone tools that they used to pound out the relatively soft volcanic rock were found all over the quarries. Here is a clip of one of the local explaining to his grandson how the Moai were built:
Spoken through a translator: “He thinks that 20 people carved this over a period of 5-6 years to this stage. These are our sections of people that are given an assignment. This is their section. You can see different ways of doing it, and you can clearly see the tonki marks and how the people were carving and going in and making these deep cuts in the rock.”
Narrator: “The channels reached around, and eventually formed a boat-like keel, until the statue could be snapped off and fully extracted.”
Ancient Aliens spends most of its time here discussing the moving of the Moai, and it’s interesting the angle that they take, because it seems that they are aware that there have been many successful experiments moving Moai with wooden sleds and minimal workers. So Ancient Aliens has to do what they do best, create a false dilemma.
AA: “But there is a unique problem with the idea of moving Moai with sleds or rollers.”
AA: “When you go to Easter Island, you don’t get the impression they had enough wood to have rollers and, in fact, in the 1700s, the first four expeditions to Easter Island never really saw a tree. That’s the real mystery of Easter Island…how can you move a multi-ton statue if you have no trees for rollers?”
So they say there are currently no trees on Easter Island. Therefore they assume there were never any trees on Easter Island, and therefore, well…aliens.
The problem with this is that there used to be a lot of trees on Easter Island, which we know because of extensive pollen samples taken from the crater lakes, as well as other methods. In fact the very reason there are no trees on Easter Island now, is probably because they used all of them while moving and lifting over 1,000 Moais over 100s of years. In other words they used all the trees.
One interesting thing about Easter Island is regarding the soil erosion. If you take a land that once had a lot of trees and cut them all down, then you will have massive soil erosion problem. This is because there would be no more root systems to hold the soil in place. Also the rains no longer have anything to stop their velocity.
The soil erosion at Easter Island is so notorious that if you type “soil erosion” into a search engine, you will see the Wikipedia page has a picture of Easter Island.
Some of the Moai actually have full bodies, they are not just heads, but because of soil erosion, even in very short time they have been covered up to their necks in soil. This is a direct result of the land being completely deforested.
So we know for sure how these Moai were cut and shaped, that is with simple tools which are found all over the quarries, and we know that if they had trees on Easter Island then there are no problems with moving them and prying them into place. And Easter Island used to have a lot of trees before their fascination with creating Moai exhausted their supply.
 “Quarry on Easter Island.” National Geographic. Web. <http://education.nationalgeographic.com/education/multimedia/quarry-easter-island/kd/?ar_a=3&ar_r=999>.
 PBS Nova. Easter Island – Secrets of Lost Empires, 2000.
 Thor Heyerdahl., 1962. “at some unidentified date prior to AD 380, the first settlers landed on Easter Island, and found a verdant island covered by trees, shrubs, and palms.” He proved this to be true from the extensive pollen samples taken from the crater lakes with the aid of 26 feet long cores from the sediments