Approximately how long ago did the neolithic revolution begin

What from the columbian exchange had perhaps the biggest impact on the world?

Is the weather changing? consider the data of severe weather that includes tornadoes occurring throughout the u. s. over the last four years. compare the severe weather for the last three years. then compare the first three months of 2017 with that data. based on previous years, what might the prediction be for weather during 2017?

What were some of the new consumer appliances that americans could purchase in the 1920s