Life Only Needed a Small Amount of Oxygen to Explode, Scientists Find

Scientists have long debated the role of oxygen in the Cambrian explosion, a period of rapid evolution that occurred around 540 million years ago. The explosion saw the emergence of a vast array of complex animal species, and many believed that a sudden surge in oxygen levels was the key factor that sparked this burst of biodiversity. However, new research suggests that this may not be the case.

According to a recent study published in Nature Geoscience, the Cambrian animals did not require as much oxygen as previously thought. The team of scientists, led by geobiologist Erik Sperling from Stanford University, analyzed sedimentary rocks formed on the bottom of ancient oceans and found that oxygen levels increased only slightly, but enough to drive significant changes in ecology.

The researchers used statistical analyses of trace metals, such as molybdenum and uranium, which are indicators of global ocean oxygen levels, to reconstruct long-term trends in oxygen levels and marine life over the past 700 million years. Their findings suggest that oxygen levels in the deep ocean did not reach modern levels until around 140 million years after the Cambrian explosion, during the Devonian period. However, oxygen levels in shallow waters may have increased enough to support the emergence of marine life.

“It’s not a huge increase in oxygen, but it might be enough to cross critical ecological thresholds, based on what we see in modern areas with naturally low oxygen,” Sperling notes.

The study’s findings expand on previous research, which found that shallow seas became oxygenated first, but atmospheric oxygen did not reach modern levels until some 50-100 million years after the Cambrian explosion. Other recent research has suggested that oxygen levels started rising in the early Ediacaran period, around 640-600 million years ago, during the first of three successive oxygen pulses that coincided with important evolutionary leaps.

However, not all scientists agree on the role of oxygen in the Cambrian explosion. Some argue that oxygen levels throughout deep time have been extremely variable, making it difficult to determine their impact on biodiversity.

The study’s lead author, palaeobiologist Richard Stockey from the University of Southampton, notes that oxygen levels in shallow waters may have increased enough to support the emergence of marine life. “From a global perspective, we didn’t see the full oxygenation of the oceans to near modern levels until about 400 million years ago, around the time that we see the appearance of large forests on land,” he explains.

The team’s research provides new insights into the role of oxygen in the Cambrian explosion and highlights the complexity of the Earth’s history. While oxygen may not have played the critical role previously thought, it still had an impact on the evolution of life on Earth.

Historical Context:

The Cambrian explosion, which occurred around 540 million years ago, was a period of rapid evolution that saw the emergence of a vast array of complex animal species. This event is considered one of the most significant in the history of life on Earth, as it marked the beginning of the development of many animal phyla that are still present today. The Cambrian explosion is often referred to as the “big bang” of animal evolution, and it is believed to have been triggered by a combination of factors, including changes in the Earth’s climate, the development of new habitats, and the evolution of new body plans.

The role of oxygen in the Cambrian explosion has been a topic of debate among scientists for many years. Some have suggested that a sudden surge in oxygen levels may have played a key role in the explosion of biodiversity, while others have argued that other factors, such as changes in the Earth’s climate or the development of new habitats, may have been more important.

Summary in Bullet Points:

• Scientists have long debated the role of oxygen in the Cambrian explosion, a period of rapid evolution that occurred around 540 million years ago. • A recent study published in Nature Geoscience suggests that the Cambrian animals did not require as much oxygen as previously thought. • The study analyzed sedimentary rocks formed on the bottom of ancient oceans and found that oxygen levels increased only slightly, but enough to drive significant changes in ecology. • The researchers used statistical analyses of trace metals, such as molybdenum and uranium, which are indicators of global ocean oxygen levels, to reconstruct long-term trends in oxygen levels and marine life over the past 700 million years. • The findings suggest that oxygen levels in the deep ocean did not reach modern levels until around 140 million years after the Cambrian explosion, during the Devonian period. • However, oxygen levels in shallow waters may have increased enough to support the emergence of marine life. • The study’s findings expand on previous research, which found that shallow seas became oxygenated first, but atmospheric oxygen did not reach modern levels until some 50-100 million years after the Cambrian explosion. • Other recent research has suggested that oxygen levels started rising in the early Ediacaran period, around 640-600 million years ago, during the first of three successive oxygen pulses that coincided with important evolutionary leaps. • Not all scientists agree on the role of oxygen in the Cambrian explosion, with some arguing that oxygen levels throughout deep time have been extremely variable, making it difficult to determine their impact on biodiversity. • The study’s lead author notes that oxygen levels in shallow waters may have increased enough to support the emergence of marine life, and that the full oxygenation of the oceans did not occur until around 400 million years ago, around the time that large forests appeared on land. • The team’s research provides new insights into the role of oxygen in the Cambrian explosion and highlights the complexity of the Earth’s history.