Get ready to dive into the fascinating world of eukaryotes! These complex organisms, including plants, animals, and fungi, are made up of cells with internal structures enclosed in membranes. And did you know that steroids play a crucial role in their membrane flexibility? That’s right, even single-celled organisms use membrane-covered structures for feeding.
But here’s the exciting part: researchers have traced the origin of eukaryotic steroids almost a billion years further back in time! This suggests that many branches of the eukaryotic family tree once made early versions of steroids. However, our branch evolved the ability to produce more elaborate ones, which may have helped us outcompete our relatives.
The new work involves testing an idea proposed decades ago by the biochemist Konrad Bloch. Bloch suggested that the chemical intermediates on the pathways he identified were, at some point in our evolutionary paths, the end products. Cells would make these less complex steroids, which played critical roles in their survival. Over time, however, our branch evolved enzymes that further modified them in ways that were advantageous.
But wait, there’s more! The researchers obtained oil and bitumen samples from sediments dated to different points in the Earth’s past and found that eukaryotes seem to have been everywhere. These protosteroids were detected in deep and relatively shallow water environments, microbial mats and pelagic habitats, shales and carbonates, as well as marine and likely lacustrine basins.
So, what does all of this mean? The researchers propose an intriguing idea that places the origin of modern eukaryotes within the geological record. Eukaryotes seem to have arisen within a geological time period named the “boring billion,” which ran from roughly 1.8 to 0.8 billion years ago. During this time, not a lot happened, and life responded by forming stable ecosystems that persisted for much of this time.
But the lack of ecological upsets may have meant that the ancestor of all modern eukaryotes faced a difficult time finding an unoccupied ecological niche. Given that challenge, the evolution of modern steroids could potentially have given them the tolerances needed to occupy more extreme environments. This could mean that modern steroids were being made, but only at levels that make their detection unlikely.
In the end, the ability to tolerate environmental extremes allowed by modern steroids could have given our ancestors an edge, allowing them to push all the other branches of the eukaryotic tree to extinction. Who knew that something as seemingly small as steroids could have such a significant impact on the evolution of complex life?
Today, researchers have discovered some remarkable evidence that suggests life on Earth, in the form of complex cells, could have existed longer than once thought. A team of scientists from the Hebrew University’s Earth Sciences Institute have found signs of grease-like molecules in a billion-year-old rock, which could suggest that the earliest forms of complex cells, known as eukaryotes, existed far before their previously assumed date of about 800 million years ago.
The evidence comes from the form of chemical signatures locked away in ancient rocks in southern Namibia. The majority of fossils that are found in sedimentary rocks are physical remains of life, such as bones, teeth, or shells. However, the fossils found in this research are known as ‘molecular fossils’- molecules and fragments that have been left behind with no trace of their original structure or function.
The molecular fossils analysed by the team show signs of a fatty acid, likely deriving from a grease-like cell membrane. The conclusions made from the study are that algae-like archea could have been around the same time as the earliest eukaryotes, changing the modern timeline of evolution.
Although this research suggests that the evolution of life on Earth could have been more complex than initially assumed, it is still difficult to decipher how life evolved over such a long time period. It is also possible that the fatty acid signature was left behind through natural processes not related to life at all.
Despite the challenges of deciphering ancient history, the research performed on the ancient rocks may signify a major scientific breakthrough, providing evidence that complex life on Earth has a much deeper, longer history than first thought.
Source: The Jerusalem Post
