Tools excavated from a cave in central Mexico are strong evidence that humans were living in North America at least 30,000 years ago, some 15,000 years earlier than previously thought, scientists said Wednesday.​ Artefacts, including 1,900 stone tools, showed human occupation of the high-altitude Chiquihuite Cave over a roughly 20,000 year period, they reported in two studies, published in Nature. "Our results provide new evidence for the antiquity of humans in the Americas," Ciprian Ardelean, an archeologist at the Universidad Autonoma de Zacatecas and lead author of one of the studies, told AFP. "There are only a few artefacts and...