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PASADENA — For the primitive organisms unlucky enough to be around 2.4 billion years ago, the
first global freeze was a real wipeout, likely the worst in the history of life on Earth. Few of the
organisms escaped extinction, and those that did were forced into an evolutionary bottleneck
that altered the diversity of life for eons.

But 2.4 billion years later, an unlikely winner has emerged from that first planetary deep-freeze,
and it’s none other than us modern industrial humans. New research from the California
Institute of Technology reveals that the world’s largest deposit of manganese (a component of
steel) was formed by the cascade of chemical reactions caused when the planet got so cold
that even the equators were icy — a condition now known as “Snowball Earth.”

In a special issue of the Proceedings of the National Academy of Sciences on global climatic
change published February 14, Caltech geobiology professor Joe Kirschvink and his team show
that the huge Kalahari Manganese Field in southern Africa was a consequence of a long
Snowball Earth episode. Kirschvink, who originated the Snowball Earth concept more than a
decade ago, says the new study explains how the drastic climatic changes in a Snowball Earth
episode can alter the course of biological evolution, and can also account for a huge economic

According to Kirschvink and his team, the planet froze over for tens of millions of years, but
eventually thawed when a greenhouse-induced effect kicked in. This warming episode led to the
deposit of iron formations and carbonates, providing nutrients to the blue-green algae that
were waiting in the wings for a good feeding.

The algae bloom during the melting period resulted in an oxygen spike, which in turn led to a
“rusting” of the iron and manganese. This caused the manganese to be laid down in a huge
45-meter-thick deposit in the Kalahari to await future human mining and metallurgy. Today,
about 80 percent of the entire world’s known manganese reserves are found in that one field,
and it is a major economic resource for the Republic of South Africa.

The Snowball Earth’s cascade of climatic chemical reactions also probably forced the living
organisms of the time to mutate in such a way that they were protected from the excess
oxygen. Because free radicals can cause DNA damage, the organisms adapted an enzyme
known as the superoxide dismutase to compensate.

Kirschvink points out that the enzyme and its evolutionary history are well known to biologists,
but that a global climate change apparently has never been suggested as a cause of the
enzyme’s diversification.

“To our knowledge, this is the first biochemical evidence for this adaptation,” says Kirschvink,
adding that the data shows that the adaptation can be traced back to the Snowball Earth
episode 2.4 billion years ago.

Kirschvink, his former doctoral student Dave Evans (now at the University of Western Australia
in Perth), and Nicolas J. Beukes of Rand Afrikaans University proposed the Snowball Earth
episode in a 1997 paper in Nature. Their evidence for the freeze of 2.4 billion years ago was
based on their finding evidence of glacial deposits in a place in southern Africa that in ancient
times was within 11 degrees of the equator, according to magnetic samples also gathered

The other authors of the PNAS paper are Eric Gaidos of the Jet Propulsion Laboratory, who
also holds an appointment in geobiology at Caltech; L. Elizabeth Bertani and Rachel E.
Steinberger, both of the Division of Biology at Caltech; and Nicholas J. Beukes and Jans
Gutzmer, both of Rand Afrikaans University in Johannesburg.

The work was supported by the NASA National Astrobiology Institute.

A detailed article on the Snowball Earth phenomenon was published in the January 2000 issue of
Scientific American.

Related Links

* Dr. Joseph Kirschvink

* Geobiology and Astrobiology at Caltech

* Proceedings of the National Academy of Sciences

* Jet Propulsion Laboratory (JPL)

* The Division of Biology at Caltech

* Rand Afrikaans University in Johannesburg