(The following is excerpted from Shift: A Future Without War.i)

This chapter has been published in the book . For ordering information

— Wire,"Mannequin"I've decided to come out of the closet.

Some hypotheses are stronger, others weaker, and some have already come and gone (and might be resurrected one day, as was?). The coming generation of research may resolve most of these issues, but new ones will undoubtedly arise and there is obviously a long way to go before significant consensus will be reached on those ancient events.

Confidential: True Confessions of a Fat Admirer" border="0" width="450" height="100"

Now I'm mature enough and confident enough to embrace who I am.

And I want all the fat chicks everywhere to know, regardless of what this deranged culture tells you, that you are beautiful, and desirable, and loved.

Ever since my confused early days of preadolescence, I've felt like I was somehow different.

In the central highlands of Mexico the Toltecs were dominantfrom the 10th to the 12th century with their major city at Tollan(Tula). Itzas arrived at Chichén about 918, and ToltecChichén was not destroyed until about 1250. A Mixtec legendtells of a ruler named Eight-Deer Ocelot-Claw, who succeeded hisfather as king of Tilantongo at age 19 in 1030, won several battles,married many wives and sired numerous children, went to Tollan,and tried to set up a bureaucratic empire at Tutupec by unitingit with Mixteca Alta and Baja. Eight-Deer had the men of the royalfamilies he conquered sacrificed, and he or his sons married theirwidows and daughters. When the ruler of Xipe-Bundle died in 1047,Eight-Deer was concerned that some of his relatives would tryto rule the city. So he allied himself with the Toltec Four-Tigerand sacrificed his half-brother Twelve-Earthquake. However, hislittle empire soon failed, and in 1063 Eight-Deer was defeated,captured and sacrificed.

I'll say it loud and say it proud:I like fat chicks.

Even though we take pride in our preferences, the life of an F.A.

Glacial till is composed of “foreign” stones that had been transported there by ice. When ice ages were first conceived, a key piece of evidence was “,” which were large stones found far from their place of origin. Erratics found in ocean sediments are called . Eventually, after plenty of controversy, scientists decided that erratics had usually been deposited by glaciers. Oceanic dropstones were deposited by melting icebergs and the land-based erratics by retreating glaciers.

What a cruel fate to be born an F.A.

Deep-ocean currents, , do not seem to have existed during supercontinental times, and atmospheric oxygen was likely only a few percent at most when the Cryogenian Period began. Canfield’s ocean-oxygenation evidence partly came from testing sulfur isotopes. As with , , and other elements, life prefers the lighter isotope of sulfur, and are two stable isotopes that can be easily tested in sediments. Canfield proposed that in pre-Cryogenian oceanic depths, , which are among Earth’s earliest life forms and produce as its waste product, abounded. Hydrogen sulfide gives rotten eggs their distinctive aroma and is highly toxic to plants and animals, as it . Hydrogen sulfide would react with dissolved iron to form iron pyrite and settle out in the ocean floor, just as the iron oxide did that formed the BIFs. The sulfate-reducing bacteria will enrich the sulfur-32/34 ratio by 3% and did so before the Cryogenian, but the Ediacaran iron pyrite sediments showed a 5% enrichment. A persuasive explanation is recycling sulfur in the oceanic ecosystem, which can only happen in the presence of oxygen.

But bone-thin women just don't do a thing for me.

Part of the hypothesis for skyrocketing oxygen levels during the late Proterozoic was that high carbon dioxide levels, combined with a continent that had been ground down by glaciers, and the resumption of the hydrological cycle, which would have vanished during the Snowball Earth events, would have created conditions of dramatically increased erosion, which would have buried carbon (the cap carbonates are part of that evidence) and thus helped oxygenate the atmosphere. Evidence for that increased erosion also came in the form of strontium isotope analysis. Two of strontium’s stable isotopes are . Earth’s mantle is enriched in strontium-86 while the crust is enriched in strontium-87, so basalts exposed to the ocean in the oceanic volcanic ridges are enriched in strontium-86 while continental rocks are enriched in strontium-87. If erosion is higher than normal, then ocean sediments will be enriched in strontium-87, which analysis of Ediacaran sediments confirmed. That evidence, combined with carbon isotope ratios, provides a strong indication of high erosion and high carbon burial, which would have increased atmospheric oxygen levels. There is other evidence of increasing atmospheric oxygen content during the late Proterozoic, such as an increase in rare earth elements in Ediacaran sediments. Although there is still plenty of controversy, today's consensus is that the Cryogenian is when , where they have largely stayed, although as this essay will later discuss, oxygen levels have varied widely since the late Proterozoic (from perhaps only a few percent to 35%).

It really is kind of like being gay, I guess.

Kirschvink is a , was soon pursuing other interests, and left his Snowball Earth musings behind. Canadian geologist had been an ardent Arctic researcher, but a dispute with a bureaucrat saw him exiled from the Arctic. He landed at Harvard and soon picked Precambrian rocks in to study, as it was largely unexplored geological territory. The Namibian strata were 600-700 million years old, instead of the two billion years that Hoffman was familiar with. In the Namibian desert, he soon found evidence of glacial till among what were considered tropical strata when created.