Signs of Life

Stalks of iron-rich minerals, each a fraction the size of an eyelash, may be evidence of the earliest life-forms to inhabit the newborn planet Earth. The tiny hematite tubes are as much as 4.28 billion years old, according to the scientists announcing the find, and they are stunningly similar to structures produced by microbes living around undersea hydrothermal vents.
Discovered in slices of rock recovered from northern Quebec, the microscopic metallic detritus—plus chemical signatures associated with ancient metabolisms—could push back the date at which life arose on Earth. If verified, these fossils would surpass 3.7-billion-year-old microbial mats found in Greenland as the oldest known traces of life.

It's easy to lose sight of how drastic of a change this is when you're dealing with billions. 580 million years is a long time. To put this in perspective, that's about how long its been since the very first animals started appearing on earth. It took 3.5 billion years to go from single cellular organisms to multicellular. Plants only started making their way onto the land about 700 million years ago.

All of is useful for understanding how evolution is able to explain the complexity and variety we see in the organisms alive today. It took billions of years to lay the foundation of the basic organelles that make up the complex structures we see today. At the start of life, there wasn't any concept of predators, so a single type of life would dominate the entire planet. Its only through major extinction events that new mutations provide unique advantages and allowed life to slowly expand.

This also has profound effects on the likelihood that Mars and possibly Venus had life earlier in their histories. The Earth started forming about 4.5 billion years ago, and until recently, the primary hypothesis is that Earth did cool enough to form oceans until about 3.8 billion years ago. This finding seems to point that the alternate hypothesis is more likely correct, and that oceans started forming about 4.3 billion years ago. This would mean that life evolved almost in synchronicity with the oceans.

It seems very likely Mars and Venus had oceans around the same time. This finding makes it seem very likely we will end up finding fossil evidence of simple organisms on Mars as we continue to explore it. As for the Galilean moons of Jupiter with their huge bodies of water, its looking more and more hopeful we will find creatures lurking below those ice covered surfaces.