Posted on February 17 2015
The earth has been around for something like 4.5 billion years, and life has been dated back to around 3.8 billion years. In all that time, one thing has been constant—change. Those first 1.3 billion years saw the planet go from a hot mess to a place with oceans and hard land. And ever since the first cells, it’s been change, change change, all the way up through the dinosaurs to the ascendancy of trouble-making mammals with opposable digits. Occasionally, scientists have found old species of plants or animals which have stayed fairly stable in their design for a long time, such as ginko trees, sharks, coelacanths, or silverfish. But recently, a paper in the Proceedings of the National Academy of Sciences describes three occurrences of a microbe that really made time stand still.Western Australia has delivered up some of the oldest evidence of early life, amongst which are fossilized remains of microbial communities that are 2.3 billion years old. At other sites in the same region, identical microbes were found to have existed in rocks 1.8 billion years old. That’s 500 million years of doin’ the same thing day in and day out. But here’s the really astounding thing: they’re stilldoing it! Right now, today, these same organisms are chugging along like there never was a Permian extinction, a Renaissance, or a first black president. How do they do it, when life on earth has gone through, and continues to go through, unimaginable changes just to survive?
The secret is a stable environment. These microbes inhabit the bottom of the deep ocean. And not only that, they snuggle into the mud from a few inches to a foot down into the bottom. It is cold, high-pressure, and dark — not very inviting conditions, but it’s always cold, high-pressure and dark. For billions of years. There is no oxygen, food comes in the form of nitrate and sulfur, and the organisms breed asexually, avoiding mutation. There aren’t any other organisms to dig up their turf or compete with them. Darwin theorized that organisms evolved into their millions of forms in response to the altered conditions in their environment. There are innumberable examples of this, but in this case his argument is proven from the negative side. If there is no change, there is no evolution. In other words, stick with a winner.
The living population of these microbes was found off the west coast of South America, but it is thought that they may be quietly hanging out under ocean floors in many parts of the world. It’s difficult to get mud cores at such depths. Further exploration will tell if, in this crazy, wild, thousand-changes-a-second world where we live, we have even more neighbors who haven’t gotten so much as a new hairdo in billions of years.