longest toothof L. melvillei,including root
longest toothof T. rex “Sue,”including root
longest toothof extinct sharkC. megalodon
Evidence for earlier multicellular life
Soft-bodied creatures presumed to have breathed oxygen
By Gwyneth Dickey
Researchers have found what may be theoldest evidence of multicellular life onEarth. Centimeter-sized fossils uncovered in 2.1-billion-year-old rock fromGabon, in west-central Africa, appear tobe examples of macroscopic life in whatwas then a sea of single-celled microbes.
Scientists believe that multicellularlife really took hold much later, in thegreat expansion of animal body plansknown as the Cambrian explosion, whichbegan about 540 million years ago.
“The discovery is fantastic because
it shows the existence of multicellular
fauna 1. 5 billion years earlier than what
we know,” says team leader Abderrazak
El Albani, a sedimentologist and paleo-
biologist at the University of Poitiers
in France. “This is important to under-
stand the evolution of life on Earth.”
Some evidence suggests a few species
of multicellular organisms may have
arisen as early as 1. 6 billion years ago,
but that evidence is controversial. El
Albani and his colleagues were thus sur-
prised to find large fossils in the newly
excavated ancient Gabonese rocks. So
far, the researchers report in the July 1
Nature, they have collected more than
250 specimens ranging in size from 0.7
to 12 centimeters.
Using detailed X-ray imaging, the teamcreated 3-D images of the fossils inside
Fossils uncovered in Gabon appear to
be examples of early multicellular life.
and out. The organisms had flat, oblong,soft bodies, with slits around the edgesand complex, patterned folds inside.
Other researchers agree that the largesize, thickness and three-dimensionalityof the organisms suggest that they wereindeed multicellular. “There does seemto be something more than just a clonalcolony of bacteria,” says paleobiologistPhilip Donoghue of the University ofBristol in England.
El Albani and his team believe thecomplex patterns and folding meanthat the creatures must have coordinated their growth through cell-to-cellsignaling, as multicellular organisms dotoday. The fossils could even be the earliest known examples of eukaryotes, cellswith membrane-bound nuclei, accord-ing to the team.
In their paper, the researchers offeredseveral lines of evidence to demonstratethat the fossils are not simply mineralformations that look like animals, or theremains of more recent creatures thatburrowed down into older sediments.
Pyrite, a sulfur-containing mineralalso known as fool’s gold, filled the fossils, providing evidence that sulfur-usingbacteria had eaten away at living tissue.
Further analysis showed that the fossils couldn’t have been made from morerecent organisms that burrowed deepinto sediments, because the surrounding rock was the same inside and outsidethe organisms’ folds.
Rock chemistry indicates the organisms lived about 30 to 40 meters deep inseawater. They probably breathed oxygen, which by that time had been building up in the oceans and atmosphere forabout 300 million years. Donoghue saysit’s exciting that scientists are “edgingback” the fossil record toward the GreatOxidation Event 2. 5 billion years ago,when oxygen began accumulating inthe atmosphere.
It’s Moby Dick
What would you get if you crossed awhale with a shark? Maybe somethinglike Leviathan melvillei, an extincthypercarnivorous sperm whale withteeth longer than any that T. rex everhad. The whale (depicted above) livedbetween 12 million and 13 millionyears ago, says Olivier lambert, a vertebrate paleontologist at the nationalMuseum of natural history in Paris. ajawbone and partial skull of the whalewere found in southern Peru in november 2008, lambert and his colleaguesreport in the July 1 Nature.
Leviathan’s longest tooth measures about 36 centimeters including the root, more than 40 percentlonger than those of today’s spermwhales. The researchers estimatethat Leviathan measured between13. 5 and 17.5 meters long—slightlysmaller than the largest adult malesperm whales of today—and fed onmedium-sized baleen whales, whoseblubber would have been a richsource of calories. — Sid Perkins
July 31, 2010 | science news | 17