Sufficient oxygen for animal respiration 1,400 million years ago
Shuichang Zhanga,1, Xiaomei Wanga, Huajian Wanga, Christian J. Bjerrumb,c, Emma U. Hammarlundd,e, M. Mafalda Costaf,g, James N. Connellyf,g, Baomin Zhanga, Jin Sua, and Donald E. Canfieldd,e,1
aKey Laboratory of Petroleum Geochemistry, Research Institute of Petroleum Exploration and Development, China National Petroleum Corporation, Beijing 100083, China;
bDepartment of Geosciences and Natural Resource Management, Section of Geology, University of Copenhagen, DK-1350 Copenhagen, Denmark;
cThe Nordic Center for Earth Evolution at the Department of Geosciences and Natural Resource Management, Section of Geology, University of Copenhagen, DK-1350 Copenhagen, Denmark;
dInstitute of Biology, University of Southern Denmark, DK-5230 Odense, Denmark;
eThe Nordic Center for Earth Evolution at the Institute of Biology, University of Southern Denmark, DK-5230 Odense, Denmark;
fCentre for Star and Planet Formation, University of Copenhagen, DK-1350 Copenhagen, Denmark;
gNatural History Museum of Denmark, University of Copenhagen, DK-1350 Copenhagen, Denmark
Contributed by Donald E. Canfield, November 27, 2015 (sent for review November 2, 2015; reviewed by Lee Kump and Jennifer Morford)
Significance
How have environmental constraints influenced the timing of animal evolution? It is often argued that oxygen first increased to sufficient levels for animal respiration during the Neoproterozoic Eon, 1,000 million to 542 million years ago, thus explaining the timing of animal evolution. We report geochemical evidence for deep-water oxygenation below an ancient oxygen minimum zone 1,400 million years ago. Oceanographic modeling constrains atmospheric oxygen to a minimum of ∼4% of today’s values, sufficient oxygen to have fueled early-evolved animal clades. Therefore, we suggest that there was sufficient atmospheric oxygen for animals long before the evolution of animals themselves, and that rising levels of Neoproterozoic oxygen did not contribute to the relatively late appearance of animal life on Earth.
Abstract
The Mesoproterozoic Eon [1,600–1,000 million years ago (Ma)] is emerging as a key interval in Earth history, with a unique geochemical history that might have influenced the course of biological evolution on Earth. Indeed, although this time interval is rather poorly understood, recent chromium isotope results suggest that atmospheric oxygen levels were <0 .1="" 1="" 3="" a="" an="" ancient="" and="" animal="" approach="" are="" atmospheric="" bacteria="" biomarker="" block.="" bottom="" carbon="" china="" column.="" comprehensive="" consistent="" contrast="" cycle="" demonstrate="" deposition="" develop="" different="" distribution="" document="" during="" dynamics="" enrichments="" evolution="" explore="" formation="" geochemical="" green="" have="" in="" inhibited="" levels="" life.="" low="" ma="" marine="" metal="" metals="" minimum="" model="" north="" of="" our="" oxygen="" oxygenated="" patterns="" presence="" present="" redox-sensitive="" results="" reveal="" sediments="" show="" simple="" sufficiently="" sulfur="" that="" the="" thus="" to="" trace="" unit="" using="" water="" waters="" we="" with="" xiamaling="" yet="" zone.="">4% of present-day levels. Therefore, in contrast to previous suggestions, we show that there was sufficient oxygen to fuel animal respiration long before the evolution of animals themselves.
atmosphere Mesoproterozoic oxygen minimum zone trace metals biomarkers
Footnotes
1To whom correspondence may be addressed. Email: sczhang{at}petrochina.com.cn or dec{at}biology.sdu.dk.
Author contributions: S.Z., X.W., H.W., E.U.H., J.N.C., and D.E.C. designed research; S.Z., X.W., H.W., C.J.B., E.U.H., M.M.C., B.Z., J.S., and D.E.C. performed research; S.Z., X.W., H.W., C.J.B., M.M.C., J.N.C., and D.E.C. analyzed data; C.J.B. and D.E.C. developed and performed O2 model calculation; and S.Z., X.W., C.J.B., E.U.H., J.N.C., and D.E.C. wrote the paper.
Reviewers: L.K., Pennsylvania State University; and J.M., Franklin and Marshall.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1523449113/-/DCSupplemental.
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