Sometimes new ideas in science come from traditional methods people used in the past. What did researchers learn from terra preta? How is bio-char different from the traditional Amazonian method of creating terra preta?

What did researchers learn from terra preta?...  Because terra preta is loaded with so-called bio-char -- similar to charcoal -- it also can pull substantial amounts of carbon out of the increasing levels of carbon dioxide in the Earth's atmosphere, helping to prevent global warming.

How is bio-char different from the traditional Amazonian method of creating terra preta?  Terra preta owes its characteristic black color to its weathered charcoal content, and was made by adding a mixture of charcoal, bone, broken pottery, compost and manure to the low fertility Amazonian soil. ... Terra preta soils were created by farming communities between 450 BCE and 950 CE..  

The BBC's Unnatural Histories presented evidence that the Amazon rainforest, rather than being a pristine wilderness, has been shaped by man for at least 11,000 years through practices such as forest gardening and terra preta.

the sphincter muscles at the end of the digestive tract is the anus.