Lack of a stable ozone layer: Explaining the delayed rise of plants, animals on land by a about 2 billion years

Amazing stuff!

"... And now we may have a better idea of why that took so long — more than 2 billion years — to happen.

According to a new ... study, Earth’s early atmosphere  ... effectively delaying the creation of a stable ozone layer that would shield complex life from much of the sun’s ultraviolet radiation (UVR). ...

a mystery that has puzzled scientists for hundreds of years.

“The origin and diversification of complex life on Earth remains one of the most profound and enduring questions in natural science,”  ...

Indeed, scientists have long wondered why land plants did not emerge on Earth until 450 million years ago, even though their progenitors, cyanobacteria, had been in existence for 2.7 billion years. Likewise, there are no fossils for complex land animals or plants before the Cambrian era (541 to 485 million years ago) despite the evidence of much older microfossils.

“The only existing explanation states that this delay is an intrinsic characteristic of evolution — that an enormous amount of time is required,”  ..."

From the significance and abstract:

"Significance

... The resulting elevated flux of UV radiation may have restricted complex life to the ocean and potentially explains the relatively late colonization of multicellular life on land.

Abstract

The origin of complex life and the evolution of terrestrial ecosystems are fundamental aspects of the natural history on Earth. Here, we present evidence for a protracted stabilization of the Earth’s ozone layer. The destruction of atmospheric ozone today is inherently linked to the cycling of marine and atmospheric iodine. Supported by multiple independent lines of geological evidence and examined through an iodine mass balance model, we find that elevated marine iodide content prevailed through most of Earth’s history. Since the rise of oxygen ~2.4 billion years ago, high marine iodide concentrations would have led to significant inorganic iodine emissions to the atmosphere, facilitating catalytic ozone destruction and resulting in atmospheric ozone instability with periodic or persistently lower ozone levels. At a global scale, unstable and low ozone levels likely persisted for about two billion years until the early Phanerozoic, roughly 0.5 billion years ago. The delayed stabilization of the Earth’s ozone layer holds significant implications for the tempo and direction of the evolution of life, in particular life on land."

Earth’s air war: Explaining the delayed rise of plants, animals on land | Yale News "A new Yale study finds that a destabilized ozone layer may have delayed the rise of land animals and plants on Earth."

Evolution of the iodine cycle and the late stabilization of the Earth’s ozone layer (no public access)