The journey of complex life on Earth started much earlier than we previously thought—possibly around 3 billion years ago. This timeline is almost a billion years earlier than some estimates suggested, revealing a gradual build-up to complex cellular life.
Initially, the simplest forms of life, called prokaryotes, emerged about 4 billion years ago. These include bacteria and archaea, which are quite basic in structure. In contrast, eukaryotes, which are more complex and include plants and animals, appeared later. They have distinct features like nuclei and organelles, allowing for more advanced functions.
A key player in eukaryotic cells is the mitochondrion, known as the powerhouse of the cell. Scientists believe that mitochondria originally started as free-living bacteria that became part of other cells. Understanding when and how this merger happened is vital for our grasp of cell evolution.
A recent study led by paleobiologist Christopher Kay from the University of Bristol used molecular clock analysis, examining genes from various organisms to create a timeline of these evolutionary events. This method estimates when species diverged by tracking genetic mutations. According to Tom Williams, a computational evolutionary biologist, the study focused on both genetic sequences and fossil evidence, creating a detailed tree of life.
The researchers identified that some of the earliest signs of complex life appeared between 2.9 and 3 billion years ago. This included the emergence of proteins essential for cell structure, like actin and tubulin. The mitochondria showed up later, about 2.2 billion years ago, coinciding with a significant increase in Earth’s oxygen levels during a period known as the Great Oxidation Event. This suggests that while eukaryotic life was developing, it thrived due to environmental changes.
This study stands out because it dives deep into what specific genes do and how they interact over time, combining insights from paleontology, molecular biology, and phylogenetics. The research sheds light on the nuanced processes that allowed life to evolve into its current complexity.
For further details, check out the study published in Nature.
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