Jim,
Quoting Clube on the original massive proto-comet: "we are dealing with a once very large comet (radius ca. 100 km) which has now degenerated into a virtually defunct cometary asteroid [i.e., no longer outgassing comet, ergo difficult to detect, with extremely low albedo--DA] (radiius ca. 10-20 Km, say) accompanied by a family of substantial meteoroids." Tunguska is definitely included in this "family."
Dating occurs on approx. 1470-1500 yr periodicity, with a minor subperiod of events at ca. 725-750 yr detectable in more recent historical millenia due to wider data sources.
Well-established (by several reliable sources, references available) dust-fog (of probable extraterrestrial origin) induced climatic-downturn events, determined by climate proxies, are approximately datable as:
10900-11000 BCE
9500-9600 BCE--ca. 1500 yr interval
7545-7650 BCE--only anomaly in list, 2000-yr interval
6100 BCE--1500-yr
3195 BCE and possibly 3114--2900 yr interval; no record anywhere yet of "missing" event
2354 BCE and probable previous multiple events (most dynamic millenium-probable additional cometary fragmentation period)--ca. 800-yr subperiod
1628 BCE--725 yr interval
1159 BCE and further activity throughout Bronze dark ages to 900 BCE--second most active period of breakup
204 BCE--1420 yr from previous major cycle event
540 CE--745 yr interval (Classical dark age)
1294-1348 multiple events, further breakup period--ca 750 yr interval
??? 725-750 yr subperiod interval means anytime now. Tunguska would likely have represented the first shot across the bow; but note that the remnants of the massive proto-comet are now of substantially reduced size, and there is less expectation of the major dramas that tormented the Bronze and Iron ages. But we are also more vulnerable now to cosmic interferences.