Navigation Links
MIT research: Life after 'Snowball Earth'

CAMBRIDGE, Mass. -- The first organisms to emerge after an ancient worldwide glaciation likely evolved hardy survival skills, arming themselves with tough exteriors to weather a frozen climate.

Researchers at MIT, Harvard University and Smith College have discovered hundreds of microscopic fossils in rocks dating back nearly 710 million years, around the time when the planet emerged from a global glaciation, or "Snowball Earth," event. The fossils are remnants of tiny, amoeba-like organisms that likely survived the harsh post-glacial environment by building armor and reaching out with microscopic "feet" to grab minerals from the environment, cobbling particles together to make protective shells.

The discovery is the earliest evidence of shell building, or agglutination, in the fossil record. The team found a diversity of fossils, suggesting life may have recovered relatively quickly following the first major Snowball Earth event. The researchers report their findings in an upcoming issue of Earth and Planetary Science Letters.

The widely held Snowball Earth theory maintains that massive ice sheets covered the planet from pole to pole hundreds of millions of years ago. Geologists have found evidence of two major snowball periods at 710 and 635 million years ago in glacial deposits that formed close to the modern equator. Fossil records illustrate an explosion of complex, multicellular life following the more recent ice age. However, not much is known about life between the two major glaciations a period of about 75 million years that, until now, exhibited few signs of life.

"We know quite well what happened before the first Snowball, but we have no idea what happened in between," says Tanja Bosak, assistant professor of geobiology at MIT, and the paper's lead author. "Now we're really starting to realize there's a lot of unexpected life here."

Ice Age armor

Bosak's colleagues, Francis Macdonald of Harvard and Sara Pruss of Smith, trekked to northern Namibia and Mongolia to sample cap-carbonate rocks the very first layers of sediment deposited after the first ice age. The team hauled the samples back to Cambridge, where Bosak dissolved the rocks in acid. She plated the residue on slides and looked for signs of fossilized life. "It's a little bit like looking at clouds, trying to pick out shapes and seeing if anything's consistent," Bosak says.

Peering at the sludge through a microscope, she discovered a sea of tiny dark ovals, each with a single notch at its edge. To get a closer look, Bosak used scanning electron microscopy to create high-resolution, three-dimensional images, revealing hollow, 10-micron-thick shells. Fossils from Namibia were mostly round; those from Mongolia, more tube-like. Most fossils contained a slit or neck at one end, from which the organism's pseudopodia, or feet, may have protruded.

Bosak analyzed the shells' composition using X-ray spectroscopy, finding a rough patchwork of silica, aluminum and potassium particles that the organism likely plucked from the environment and glued to its surface.

Bosak says these single-celled microbes may have evolved the ability to build shells to protect against an extreme deep-ocean environment, as well as a potentially growing population of single-celled species, some of which may have preyed on other organisms.

A Snowball window

"We can now say there really were these robust organisms immediately after the first glaciation," Bosak says. "Having opened this kind of window, we're finding all kinds of organisms related to modern organisms."

The closest modern relative may be testate amoebae, single-celled microbes found in forests, lakes and peat bogs. These tiny organisms have been known to collect particles of silica, clay minerals, fungi and pollen, cementing them into a hard cloak or shell. Bosak says testate amoebae were extremely abundant before the first Snowball Earth, although there is no robust evidence that the plentiful protist evolved its shell-building mechanism until after that ice age.

Bosak's guess is that the post-glacial environment was a "brine" teeming with organisms and newly evolved traits. She says the group plans to return to Mongolia to sample more rocks from the same time period, and hopes other researchers will start to investigate rates of evolutionary change in similar rocks.


Contact: Caroline McCall
Massachusetts Institute of Technology

Related biology news :

1. Geisinger research: Antimalarial drug prevents diabetes in arthritis patients
2. K-State research: Freshwater pollution costs US at least $4.3 billion a year
3. Toothsome research: Deducing the diet of a prehistoric hominid
4. Harmonizing biobank research: An achievable world-wide goal
5. Lombardi research: Monoclonal antibodies primed to become potent immune weapons against cancer
6. UC Davis bench-to-bedside research: Promising treatment in clinical trials
7. Stem cell research: From molecular physiology to therapeutic applications
8. Nervy research: Researchers take initial look at ion channels in a model system
9. Dog bites research: UAB testing software to teach kids, dogs to interact safely
10. Consent forms for research: Have they improved in 25 years?
11. New research: Sugar substitutes help reduce caloric intake without overeating or hunger
Post Your Comments:
(Date:4/28/2016)... BANGALORE, India , April 28, 2016 ... subsidiary of Infosys (NYSE: INFY ), and Samsung ... global partnership that will provide end customers with a ... and payment services.      (Logo: ... for financial services, but it also plays a fundamental part ...
(Date:4/19/2016)... -- The new GEZE SecuLogic access control ... system solution for all door components. It can be ... interface with integration authorization management system, and thus fulfills ... dimensions of the access control and the optimum integration ... considerable freedom of design with regard to the doors. ...
(Date:4/13/2016)... 13, 2016  IMPOWER physicians supporting Medicaid patients in ... new clinical standard in telehealth thanks to a new ... higi platform, IMPOWER patients can routinely track key health ... mass index, and, when they opt in, share them ... to a local retail location at no cost. By ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... June 23, 2016 Houston Methodist Willowbrook ... Cy-Fair Sports Association to serve as their official ... Houston Methodist Willowbrook will provide sponsorship support, athletic ... with association coaches, volunteers, athletes and families. ... Cy-Fair Sports Association and to bring Houston Methodist ...
(Date:6/23/2016)... --  EpiBiome , a precision microbiome engineering company, today ... from Silicon Valley Bank (SVB). The financing will allow ... drug development efforts, as well as purchase additional lab ... been an incredible strategic partner to us – one ... provide," said Dr. Aeron Tynes Hammack , EpiBiome,s ...
(Date:6/23/2016)... Ky. , June 23, 2016 ... two Phase 1 clinical trials of its complement ... placebo-controlled, single and multiple ascending dose studies designed ... pharmacodynamics (PD) of subcutaneous injection in healthy adult ... subcutaneously (SC) either as a single dose (ranging ...
(Date:6/23/2016)... ... June 23, 2016 , ... ClinCapture, the ... Convention Center and will showcase its product’s latest features from June 26 to ... a scientific poster on Disrupting Clinical Trials in The Cloud during the conference. ...
Breaking Biology Technology: