Over the last few millennia, we've invented a series of technologies … that have made it progressively easier and easier for us to externalize our memories, for us to outsource this fundamental human capacity.

This quote is from writer Joshua Foer's 2012 TED Talk about how people can improve their memories. The quote means that we as humans have invented technologies allowing us to "outsource" our memories so that we don't have to remember them ourselves. Some of these technologies include written language and computers. As a result of these mental short-cuts, we have lost much of our capacity to remember things. Watch the full TED Talk here: Joshua Foer - Feats of Memory Anyone Can Do