Many have come to expect science to be the final arbiter for questions of this kind. In this case this early radiocarbon date raises more questions than it provides answers. The dates arrived at are so at odds with those obtained through other established means that many scholars, including me, are withholding final judgment until more information becomes available while exploring all options.
To some, khat, variously spelled cott or qat, is known as "the flower of paradise". The leaves are chewed by many people in countries like Yemen, Somalia and Ethiopia, in much the same way that coca leaves are chewed in South America. It's a social drug used by millions of people, and in Muslim countries it offers a high that is not banned by the Koran.