How Long Did Microbes Rule the Earth?
Who says they ever stopped ruling the Earth? In fact, it is safe to say that microbes have been the dominant life form on our planet for most of its history. At any given moment, there are 10 times the number of microbes in your body using it to get food, move themselves around from place to place, and as a safe environment to reproduce in, compared to the number of your own cells. This remarkable fact highlights the enduring prominence of these tiny organisms in Earth's ecological balance.
The Long History of Microbial Life
Earth is estimated to be about 4.5 billion years old, and for much of that history, it has been home to life in one weird form or another. Some scientists believe life appeared the moment our planet's environment was stable enough to support it. The earliest evidence for life on Earth comes from fossilized mats of cyanobacteria called stomatolites in Greenland that are about 3.7 billion years old. These bacteria, which are still around today, are already biologically complex. They have cell walls protecting their protein-producing DNA, suggesting that life must have begun much earlier.
Furthermore, there are hints of life in even more primordial rocks. 4.1-billion-year-old zircons from Western Australia contain high amounts of a form of carbon typically used in biological processes. This provides additional evidence supporting the hypothesis that life on Earth may have originated even earlier, perhaps around 3.8 billion years ago. Supporting these theories, a recent study suggests that the earliest evidence of life on Earth could be dated to approximately 3.4 billion years ago, with life appearing 300 million years before that. This would mean that life has been on Earth for over 4 billion years, with the first 3 billion years featuring microbial evolution.
The Last Universal Common Ancestor (LUCA)
The journey of life on Earth can be traced back to the Last Universal Common Ancestor (LUCA), an hypothetical organism that gave rise to all living organisms. LUCA represents the earliest known living entity, from which all species on Earth today are direct descendants. This unbroken and incredibly diverse line of gene-passers-on represents the remarkable continuity of life. Wikipedia has an informative timeline of the evolutionary history of life, highlighting the incredible complexity and interconnectedness of all living organisms.
The Evolutionary Journey
The timeline of life on Earth is a continuous journey, with LUCA representing the starting point. All species today have evolved for exactly the same amount of time. This interconnected history underscores the intimate relationship between all living beings. Imagine a family tree where every branch represents a different species, all tracing back to a common ancestor. This vivid imagery helps to visualize the incredible journey of life on Earth.
Support for the study that supports these theories is crucial. If the new study garners additional geological research support, it would indicate that life could have first appeared on Earth while its newly filled ocean basins were still close to boiling. This would place the origin of life just two to three hundred million years after Earth's very hot and violent formation.
Understanding the early history of life on Earth can help us better comprehend the resilience and adaptability of microbiomes. Scientists continue to explore the theories behind the origin of life, pushing the boundaries of our knowledge and expanding our appreciation for the complexity of our planet's ecological systems.