Here's an oldie (7 Jul 99):Evolution in Your FaceLake Victoria, Africa's largest lake, is home to more than 300 species of cichlids. These fish, which are popular in aquariums, are deep-bodied and have one nostril, rather than the usual two, on each side of the head. Seismic profiles and cores of the lake taken by a team headed by Thomas C. Johnson of the University of Minnesota, reveal that the lake dried up completely about 12,400 years ago. This means that the rate of speciation of cichlid fishes has been extremely rapid: something on average of one new species every 40 years!
by Patrick Huyghe
Omni
Sahara's abrupt desertificationGerman scientists, employing a new climate system model, have concluded that this desertification was initiated by subtle changes in the Earth's orbit and strongly amplified by resulting atmospheric and vegetation feedbacks in the subtropics. The timing of this transition was, they report, mainly governed by a global interplay among atmosphere, ocean, sea ice, and vegetation... the model led to the conclusion that the desertification of North Africa began abruptly 5,440 years ago (+/- 30 years). Before that time, the Sahara was covered by annual grasses and low shrubs, as evidenced by fossilized pollen.
by Harvey Leifert
http://www.dailymail.co.uk/sciencetech/article-2151143/Climate-change-wiped-worlds-great-civilisations-4-000-years-ago.html ~ ignoring the GlobullWharming stuff, the date for the fall of the Harrapan civilization (with large cities) is right there at the same mark.