Study suggests complex life was present on Earth 2.33 billion years ago
An exhaustive genetic analysis of modern-day organisms has revealed new insights into Earth’s earliest forms of complex life. The findings, reported by MIT earth scientists today in Nature, suggest that eukaryotes — the domain of life comprising animals, plants, and protists — were present on Earth as early as 2.33 billion years ago, right around the time when oxygen became a permanent fixture in the atmosphere. This new time-stamp for ancient life significantly predates the earliest sign of eukaryotes found in the fossil record —1.56 billion-year-old macroscopic fossils that scientists widely agree are the remains of multicellular algae-like organisms. The MIT researchers arrived at their estimate not by examining rocks for fossil evidence but by using a technique called “molecular clock analysis.” This approach involves first sifting through DNA databases to trace the evolution of particular gene sequences across hundreds of modern species. Then, using ages derived from the fossil animal and...