"Descubriendo un milenio de monotonía: cómo era la vida en la Tierra durante mil millones de años" | Ciencia | EL PAÍS English

Si comprimimos los 4.54 mil millones de años de historia de la Tierra en un solo año, la vida primitiva habría surgido a principios de enero, antes de que finalizara febrero. Sin embargo, los organismos con células nucleadas, similares a las nuestras, no aparecerían hasta agosto. Desde ese momento hasta noviembre, prácticamente no habría ocurrido nada nuevo. Estos tres meses, en el contexto de la analogía, representan mil millones de años: un lapso de tiempo inconcebiblemente extenso. Recientemente, un nuevo estudio ha contribuido a iluminar esta brecha al detallar con precisión la lentitud con la que la vida evolucionó durante ese periodo.

Roughly 2.5 billion years ago, Earth entered the Proterozoic Eon, the third of its four major geological eras, which lasted until 538 million years ago. By that time, life had already existed for at least 3.8 billion years but remained limited to simple, bacteria-like organisms known as prokaryotes. During the 1.5 billion years of the Proterozoic, a critical evolutionary milestone occurred: approximately 1.8 billion years ago, cells with nuclei — eukaryotes — emerged. These cells would eventually form the foundation of all multicellular life, from bees and sponges to oak trees and any other multicellular being.

However, after this revolutionary step, life seemed to stagnate. For about a billion years, evolutionary progress slowed to a crawl, a phenomenon paleontologist Martin Brasier famously labeled the “Boring Billion.” “Our analysis shows that during the so-called Boring Billion, eukaryotic diversity was very stable, and species turnover rates was quite low,” explains paleobiologist and geobiologist Shuhai Xiao of Virginia Tech, co-director of the new study published in Science, which compiled and analyzed the Proterozoic fossil record to investigate the life that populated the seas in this period. “In this sense, the Boring Billion was truly boring,” Xiao confirms.