The researchers examined sedimentary rocks in
south Oman, and found an anomalously high amount of distinctive
steroids that date back to 635 million years ago, to around the end of
the last immense ice age. The steroids are produced by sponges - one of
the simplest forms of multicellular animals.
The researchers argue that the discovery of the sponges is evidence
for multicellular animal life beginning 100 million years before the
Cambrian explosion, a well-studied and unique episode in Earth history
that began about 530 million years ago when, as indicated by the fossil
record, animal life diversified rapidly.
The discovery can help scientists reconstruct Earth's early
ecosystems and explain how animal life may have first evolved on the
"Our findings suggest that the evolution of multicellular animals began earlier than has been thought," said Gordon Love
an assistant professor of Earth sciences, who led the research group.
Love began working on the project while he was a postdoctoral
researcher at MIT. "Moreover, sponges live on the seafloor, growing
initially in shallow waters and spreading, over time, into deeper
waters, implying the existence of oceanic environments which contained
dissolved oxygen near the shallow seafloor around 635 million years
According to Love, the climatic shock of the extensive glacial
episodes of the Neoproterozoic era (1000-542 million years ago) likely
caused a major reorganization of marine ecosystems, perhaps by
irrevocably altering ocean chemistry.
"This paved the way for the evolution of animal feeders living on
the seafloor," he said. "We believe we are converging on the correct
date for the divergence of complex multicellular animal life, on the
shallow ocean floor between 635 and 750 million years ago."
The steroids that Love and his colleagues observed in the Omani
rocks are essential biochemicals present in the cell membranes of the
sponges, and help provide the membranes with structural support. The
sponges are a few millimeters in size, immobile, and were filter
feeders existing on the seafloor.
The sponge findings emerged from a project Love was working on at MIT (with Roger Summons
a professor of geobiology) in collaboration with Petroleum Development
Oman. Using state-of-the-art techniques, he and his colleagues analyzed
64 Neoproterozoic-Cambrian sedimentary rock samples from the South Oman
Salt Basin (SOSB), a region known for some of the best preserved rocks
in the world. The researchers also established a robust stratigraphic
and temporal framework for the SOSB rocks as part of their analysis.
Next, Love and his colleagues plan to screen other Neoproterozoic
sedimentary rocks for animal steroids just before and through the
Sturtian and Marinoan glaciations, the greatest ice ages known to have
occurred on Earth during 850 to 635 million years ago.
"We aim to investigate the environmental context by which multicellular animal life became viable and flourished," he said.
Love obtained his Ph.D. in chemistry from the University of
Strathclyde (Scotland). He was a recipient of the prestigious Natural
Environment Research Council Postdoctoral Fellowship to carry out
organic geochemical research at the University of Newcastle (England).
He joined UCR's Department of Earth Sciences in January 2007 after his
postdoctoral appointment at the Massachusetts Institute of Technology.
Love has co-authored 50 research papers in international
peer-reviewed scientific journals on petroleum geochemistry,
geobiology, cosmochemistry, solid state nuclear magnetic resonance
(NMR) spectroscopy and analytical chemistry.
Besides researchers at MIT, Love was joined in the study by
colleagues at Geoscience Australia; the University of Newcastle upon
Tyne, United Kingdom; the California Institute of Technology; and the
University of Nottingham, United Kingdom.
The four-year study was funded by Petroleum Development Oman; the
NASA Exobiology Program; the National Science Foundation Division of
Earth Sciences; the Agouron Institute; and the NASA Astrobiology
Photo Caption: Gordon Love is an
assistant professor in the Department of Earth Sciences at UC
Riverside. Image credit: Love lab, UC Riverside.
Photo Caption: UC Riverside's Gordon Love examining rock strata in northern Oman. Image credit: David Fike, Caltech.
Photo Caption: Boxes of sediment core
laid out in the core shed at Petroleum Development Oman headquarters.
Total drillcore is cut into pieces of a few meters length, archived,
covered and stored for later sampling. Image credit: David Fike,
More about Gordon Love
Department of Earth Sciences
More about Oman (source: BBC)
MIT news release
National Science Foundation news release