What is the difference between Paleolithic and Neolithic cultures?

Alan Bomhard (1996) tries to keep Afro-Asiatic in within Nostratic, despite his admission that Proto-Afroasiatic is very different from the other members of the proposed linguistic Nostratic superfamily. As a result he suggests it was probably the first language to have split from the Nostratic speech community. Whatever was the case; by 8,000 BCE the Natufian culture itself had begun to disperse. In Palestine, Natufian developed into the Pre-Pottery Neolithic A (PPNA) culture, first identified by Kathleen Kenyon (1906-1978) in her 1950s excavations at Jericho. Kenyon also remarked at the hiatus and seeming abandonment of PPNA sites, and was followed by a limited extent of the PPNB culture that was very different. Rectilinear dwellings in the PPNB, from 7,000 BCE, replaced the round beehive dwellings seen since Natufian times, in the PPNA period. Since the 1960s, however, it has been shown that PPNB developed in an unbroken sequence from the Natufian cultures north of Damascus, forging a link between Palestine, Mesopotamia and the Anatolian cultures of Catal Huyuk, and Halicar, with which it shares some similarity. It has been suggested that this northern part of the range was developing as Proto-Semitic. Certainly, there is evidence that the PPNB culture, spread southwards to sites in Israel, lasting until 6,000 BCE ending with the brief spread of a more arid climate through the region. Christopher Edens (2001) has reported a bladelet tradition in South Western Saudi Arabia, possibly synchronous with the Epi-Paleolithic spread of tools of the Arabian bifacial tradition which lasted from 5,000 - 3,000 BCE characterised by beautifully pressure-flaked arrowheads and knives. They also used scrapers and awls or drills, probably for working leather and making beads. The Bifacial tradition, seems to have been the period during which a hunting and gathering way of life was progressively replaced by a lifestyle of nomadic pastoralism from the north, which has since then characterised the Peninsula. This, it has been suggested, saw the first spread of the Semitic languages throughout Arabia.