Research conducted by scientists from Denmark and Australia has uncovered new evidence for the metabolic complexity of early life on Earth.1 This team studying 3.5-billion-year-old rocks from northwestern Australia recovered sulfide deposits that represent the activity of ancient sulfate-reducing microorganisms. The sulfide deposits’ association with organic carbon residue further supports their biological origin, meaning that complex sulfate-reducing pathways existed. In the words of the researchers, “Sulphate reduction is a complex metabolic process requiring advanced membrane-bound transport enzymes, proton motive force generation by ATPase and other charge separation proteins, and the genetic regulation of protein synthesis through DNA and RNA.”2
Geological conditions indicate that at the time of sulfide formation the temperatures were moderate. This means that the sulfate-reducing bacteria were not thermophiles—microbes that live under high temperature conditions—rather they were mesophiles—microbes that require moderate temperatures. This finding runs counter to the expectations of one of the most popular evolutionary origin-of-life models. According to this model, mesophilic sulfate-reducing microbes should be latecomers with thermophilic sulfate-reducing organisms appearing at the base of the evolutionary tree.
This and other new evidences for the complexity of early life on Earth represent some of the most exciting origin-of-life discoveries around.3
- Yanan Shen, Roger Buick, and Donald E. Canfield, “Isotopic Evidence for Microbial Sulphate Reduction in the Early Archaean Era,” Nature 410 (2001), 77-81.
- Shen, Buick, and Canfield, 77-81.
- For information on three additional discoveries that evince early and complex life forms on Earth, see Fazale R. Rana, “Early Life Remains Complex,” Facts for Faith 7 (Q3 2001), in press.