Archaeologist

An archaeologist (考古学者) is a particular type of historian who ventures out into the field to find ancient ruins and study them first-hand. They are interested in the cultures of lost civilizations.

Role and Duties
Archaeologists work to uncover things lost beneath the earth over time, and are eager to make new discoveries about the past. Archaeologists serve a most invaluable role of piecing together the development of countries, people, and cultures.

Archaeologists are not essential to a pirate crew; very few crews are known to have an archaelogist crewmate. However, they are far from useless since their knowledge and experience makes finding ancient treasures easier. For example Robin discovered where the "Lost City of Gold" was in one day, something that took Enel a long time to accomplish.

Void Century Censorship
The World Government does not mind archaeology taking place. However, should any archaeologist (or any person at all) research the Void Century or the Poneglyphs, they risk being sent to jail or killed, and if not captured, a very high bounty may be placed on their head.

Ohara Island boasted the most famous archaeologists in the world, and their Tree of Knowledge held the history of countries from around the world. They were eventually destroyed when the World Government found out they were researching forbidden histories; all save Nico Robin, who had a bounty put on her head as a result of her escape from death, were killed.

Most people in One Piece seem uninterested in the past and are unaware of the Void Century. Archaeologists are not completely scorned by people (unless they research the forbidden histories, then they are considered evil) around the world. However, due to the Ohara incident there appears to be few archaeologists left.

Trivia

 * Though Robin's role on the ship seems a little odd, it was not unheard of for there to be at least one crew member who was knowledgeable on the value of items such as jewels, other treasures or even merchant cargo, along with knowledge on where they originate from.
 * In raids and attacks on others, time along with carry capability of both a ship and its crew would have limited what items the pirates could steal, having someone with knowledge on the most valuable of any given set of items would have proven invaluable to any pirate crew.