Pre-Pottery Neolithic A (PPNA) and Pre-Pottery Neolithic B (PPNB) [:] Agriculture and domesticated plants and animals appear only in PPNB. . . . Within PPNA, humans remained gatherers but lived in more permanent settlements for the first time. . . . Axes associated with this period are small and delicate, used for light carpentry but not suited for felling trees or other massive woodworking tasks. In PPNB, the tools have evolved to much larger and heavier axes. . . . they were used to cut down trees and complete various building project. . . .The round and oval structures of earlier domiciles were replaced by rectangular structures in PPNB. . . "Evidence tells that us that for each home, approximately 10 wooden beams were needed. Prior to this, there were no homes with wooden beams."
[I]n the Judean hills . . . changes during the PPNA–PPNB transition at the onset of the Levantine Moist Period (ca. 8000 cal B.C.) when conditions for agriculture improved. . . . villagers added heavy-duty axes to a toolkit they had used for carpentry and began to clear forests for fields and grazing lands. Sustainable forest management continued for the duration of the PPN until the cumulative effects of tree-felling and overgrazing seem to have led to landscape degradation at end of the Pre-Pottery Neolithic C (PPNC), when a cold, dry climatic anomaly (6600–6000 cal B.C.) may have accelerated the reduction of woodlands.
Much of what is loosely called the Neolithic revolution is really talking about the events that happened at the PPNA-PPNB transition point in the Near East.
It isn't entirely clear to me that populations that received the Neolithic revolution from incoming populations, rather than inventing it locally, experienced the PPNA phase at all. These areas may have skipped directly from a hunter-gatherer society to a PPNB or higher level of technological development without passing through the intermediate PPNA stage.
One implication of this kind of stage skipping technological expansion is that less technologically distinct early PPNA populations in the Near East from which PPNB populations emerged may have been more able than early Neolithic populations from other regions to assimilate prior hunter-gather populations that didn't participate in developing the Neolithic technologies themselves.
In a scenario where civilizations that are culturally daughters of the Near Eastern Neolithic where food production and the associated technologies were developed skipped immediately to post-PPNA or maybe even post-PPNB stages, the extent to which the critical stage expanded in all directions almost simultaneously once it had reached the critical point where it was superior to hunting and gathering in a large swath of ecological niches, is accentuated.
If, for example, the Egyptians and Indus River Valley start their Neolithic revolutions at PPNC, rather than PPNA, then PPNC reached them within just two hundred years or so of the time it emerges in the Near East and has a much clearer push factor to drive its emergence from the Near East to new territories (the cold, dry climatic anomaly). This is a series of mass migrations that would have been dramatic events of historic proportions in the eyes of anyone experiencing them, on the scale of the Biblical book of Exodus, if anyone had been able to write them down or accurately recount them in oral histories.
In contrast, if you think about the Neolithic emerging in the Near East two thousand years before it appears elsewhere, the pace of its expansion seems veritably glacial and is has less of a well motivated climatic dynamic to push its expansion. This looks more like the kind of rudderless diffusion and osmosis scenarios that many computer models generate, in which individually insignificant decisions of one household at a time to go over the the next hill from the one they grew up in only looks like a dramatic mass migration through someone with a time-lapse photography like perspective that no one actually participating in it would have realized was happening.
On the other hand, perhaps I have it backward. Perhaps, a lot of what seems like late Upper Paleolithic hunter-gatherer activity that seem to have involved brought about major changes in both North African and Southern European population genetics are better described as PPNA than as late UP hunter-gatherers. In these areas (which are geographically contiguous and similar in climate to the places where the PPNA emerged in the Near East), the PPNA rather than a later PPNB wave may have been the most powerfully formative population genetic source for later populations in the same region.
An Upper Paleolithic to PPNB or PPNC leap with less admixture may have been something more particular to the Danubian Neolithic, where PPNA technologies outside the more narrow ecological niche where they emerged did not translate to new climates as well until they were more advanced, rather than representing a general feature of Neolithic expansion in Western Eurasia and North Africa.
The study is also notable for showing how an obvious archaeological feature (round v. rectangular buildings) could emerge naturally and independently from a less visible technological development (better axes), which in turn turns out to be intimately linked to more reliable and productive horticultural production that made it important to figure out how to efficiently clear land and hence to develop better tools to accomplish that end. The end architectural impact was an indirect but inevitable unintended benefits of improving carpentry in general in order to make more room for farms by cutting down forests.
This kind of apparent coincidence with fundamental technological sources can help explain why there are such striking architectural parallels between early Near Eastern and Anatolian Neolithic structures and structures that started to be built in the American Southwest by a totally independent maize and bean Neolithic food production system almost eight thousand years later in the New World. The earliest stages of architectural development in Mesopotamia, for example, are very similar to the earliest stages of architectural development in a geographic region roughly within the boundaries Mexico as it existed in the early 19th century. But, a Book of Moron style transmission of technologies via migrations across the ocean make no sense to explain these similarities when one considers that forms seen in the New World had been obsolete in the place where these architectural forms are seen first on the globe eight millenia earlier (in addition to having no archaeologically or genetically supported evidence to support it).
More deeply, it suggests that the technology and climate driven long term path of history is much more tightly constrained by the non-obvious universal implications of laws of physics and biology that drive engineering and horticulture than a naive, "anything can happen at any given point in history" conception where slight random differences in initial conditions and innovations can produce radically different end results apart from some of the cultural window dressing put on the largely universal tends.
In other worlds, absent outside intervention, technology may be constrained to a high level of probability to develop in a highly specific sequence with material cultures and forms of social organization that natural world limitations turn out to specify at a quite high level of detail. For example, maybe there are similarly deep reasons why early metal age cultures are naturally predisposed to develop particular kinds of linguistic structures (like base twenty numbers), political systems led by priest-kings who preside over rituals involving animal and human sacrifice, and polytheistic religions that divided the forces of nature into portfolios of influence for various deities, even if they develop totally independently. But, of course, the precise names of the polytheistic gods in question and most popular precise visual motifs that emerge to sheath this universal tendencies are pretty much chaotic (i.e. highly sensitive to random variations in initial conditions and inherently unpredictiable). (Likewise, today, the technological developments that have given rise to the transition from industrial to post-industrial economies may have hidden and indirect drivers that encourage secularism and undermine the ceremonially oriented mainline monotheism that prevailed in the Industrial Age.)
In a related observation, it is also worth noting that emerging view that the large stone structures that are the diagnostic and nominative feature of the Megalithic culture are increasingly being interpreted not simply as outdoor astronomical calenders, but also as the most robust skeleton of what were actually large, predominantly timber buildings when they were erected. These massive, precision timber structures align the Megalithic culture with a stage of technological development and material culture no earlier than PPNB. And, in much of Western Europe, the Megalithic culture appears to have been the initial and original Neolithic culture in the region, coming immediately after a hunter-gatherer phase with no intermediate steps. Notably, the Megalithic culture emerged at and beyond the fringes of the areas in the Mediterranean basin most similar to the Fertile Crescent areas where the Neolithic was invented by the people of PPNA. The Megalithic culture was out of the sweet spot for the more fragile PPNA form of food production. So, the expansion of the Megalithic culture, like the Danubian Neolithic, may have similarly been a technological stage skipping one rather than a more gradual and continuous one.