Life Before Fossils

king-kong-killing-pterodactyl-1024x766Seeing may not always mean believing, but when it comes to living things from millions of years ago, it helps. A skeptic these days would have difficulty doubting the reality of dinosaurs given all the bones in museums and the reconstructions come to life in countless films. When embedded in an adventurous and romantic story, oversized reptiles and even King-Kong-size versions of our primate ancestors put persuasive passion and flesh on the cool scholarship of paleontologists.

The trouble is that the stuff of the usual fossil history—old bones, insects trapped in amber, hardened imprints of early plants–date back no more than 600 million years. Such a number may seem very old, but from another perspective it is not nearly old enough. For life has been traced back three billion years before that, six times further into the past. It’s not surprising that life from that long ago is not the material for theme parks or movies about entrepreneurs like Carl Denham who searched out Kong’s island. For life was small for the first three billion years, with no animals or plants as such. There were only microbes, single cells that gradually acquired the complexities of modern cell life—a nucleus, the hunger for oxygen, sexual reproduction. But there are no two-billion-year-old bones from which to reconstruct cellular giants, no fossils to serve as relics to fire the romantic imagination.

Or almost none.

Stromatolites in Australia, probably looking much as they did 3.5 billion years ago. (www2.estrellamountain.edu)

Microfossils from 3.5 billion years ago (www2.estrellamountain.edu)

To find them, you have to search for the oldest rocks. Try Australia, Greenland, or South Africa for those that date back almost four billion years. Slice them thin, put them under a microscope, look for microfossils measuring a fraction of a millimeter, their cell walls mineralized into tough material.

 

 

stromatolites layers pinterest

petrified stromatolite (pintrest)

 

 

And look for petrified stromatolites, the layered habitats of colonies of bacteria that filtered sea water for nutrients as far back as 3.5 billion years.

 

 

 

But could the tiny remains and traces of chemicals from billions of years ago become the attractions of crowded museums and movie fantasies? Could they find their place in popular culture as both entertainment and subtle education, as dinosaurs and apes have?

I believe they could.  It’s not difficult to imagine oversized reproductions of ancient microbes which kids could walk through while trying to avoid getting snagged on strands of DNA or thrown off-balance by the cell’s motion from its flagellum, its tail. And climate change sets the stage for a movie thriller about bacteria mysteriously resurrected from three billion years ago that thrive on carbon dioxide and for whom oxygen is poison.

Then our wonder at the marvels of our pre-human ancestors would reach back through the full history of life.

 

Most of Your Cells Aren’t Yours

“All told, the [tiny] microbes in your body outnumber your own [much larger] cells by ten to one and can weigh as much as or more than your brain—about three pounds in an average adult. Each of us is thus both an organism and a densely populated ecosystem, with habitats harboring species as different from one another as the animals in a jungle and a desert.” Thus writes Stanford University microbiologist Nathan Wolfe in the 1/2013 issue of National Geographic. The more we find out about our bacteria, the more we might want to rethink who, biologically, we are.

Bacteria under a toenail. (allergiesandyourgut.com)

Bacteria under a toenail. (allergiesandyourgut.com)

The “habitats” that house these communities of bacteria and other microbes include our gums, guts,  genitals, underarms, inner elbows, tongue and throat, and the backs of our ears. Only a few species of bacteria make us sick. Others digest our food, make our vitamins, train our immune systems, moisturize and protect out skin. The bacteria that helps us digest milk crowd into the vaginal canal when a baby is passing through to help prepare it for breast milk.

There is an eerieness to me about all this. In many cultures people believe that their ancestors are always nearby, watching over them, helping or interfering with their lives. And devout Christians invoke deities, angels, and saints for assistance. So here for us secularists are our own ancient ancestors, the bacteria, every bit as with us and in us and influential as any holy spirit is thought to be.

What’s also eerie is that bacteria have a long history of becoming a part of other organisms, literally. Billions of years ago bacteria that could process light and excrete oxygen were absorbed into other cells and turned into the photosynthesizing chloroplasts of green plants. Other bacteria that boosted cellular energy were so useful to other cells that they became incorporated as the energizer mitochondria found in nearly all cells. In humans, bacteria don’t seem to have settled in as part of the furniture—yet—but they have been called “the forgotten organ.” Bacteria can be very good at making themselves indispensable.

We think of ourselves as a relatively new species, set off from the rest of nature by our brains. And indeed we are both new and different in some ways. But surely the way that bacteria have become integral parts of us, repeating a pattern billions of years old, reminds us what ancient creatures we really are.