The question of when human settlers first arrived in North America is not an easy one to answer, but archaeologists now have another piece of useful evidence to work from - a new study of 14,000-year-old poop. Found in the well-known Paisley Caves in Oregon, the faeces add to the growing consensus that human history on the continent pre-dates the Clovis culture thought to have been established about 11,500 years ago. While the DNA of this dried-out dung has been analysed before, the latest study takes a different tack, looking for traces of lipids - the fatty biological materials, including...