Life Emerged Just Once?

Star Trek is my religion. I grew up imagining a future of contact with alien beings who we could learn from. Back in 1950 physicist Enrico Fermi asked, “But where is everybody?” 

If our galaxy is teeming with planets and our planet is nothing special, why haven’t we encountered any evidence of aliens? We have never found any evidence that aliens visited here in the past. And our radio telescopes have never picked up the equivalent of old I Love Lucy TV shows from other planets.

Merlie and I recently toured the Jet Propulsion Laboratory and watched as the Europa Clipper was being prepared for launch this fall. Its 10-year mission? To search for conditions conducive to life on Jupiter’s moon Europa. I am very happy for all of the work done by NASA and other organizations to search for any sign of life out there. The wonderful James Webb space telescope is also looking at exoplanet atmospheres for such signs.

But I have become intrigued by a related question. As we search for life on other worlds, what about life here on Earth? Humans and chimps share about 98% of our DNA. We even share about 60% of our DNA with bananas. All living things on Earth need similar genetic machinery to do the basic things to survive.

We now know that there is a Last Universal Common Ancestor (LUCA) of all living things on Earth. It lived around 3.5 billion years ago. Meaning that all living things from rats to rutabagas to rotifers came from one emergence of life.

Our search for life in space includes what we consider to be harsh environments, like on Mars or Europa. But life on Earth is obviously not harsh. Earth is teeming with life. But it is all from one origin. If Earth is so conducive to life, why didn’t other forms of life emerge independently? Why isn’t it happening now?

Various answers have been proposed. It’s possible that current life out-competed others and the others died out before leaving any lasting trace. It’s possible that our life forms would eat any competing life forms. I don’t find this satisfying. I am with Fermi. Where are these other life forms?

Why does this matter? I think there are valid ethical issues at stake. What if Earth is the only place with life in the universe? Doesn’t that give us a responsibility to ensure its survival?

A friend told me this argument makes no sense. If we are the only life and we go away, then no one will be around to miss us. I don’t find this satisfying, either.

Social scientist Brian Klaas recently published a book Fluke that I plan to write more about. He writes about the many unlikely events that led to the world we live in. One of these is how we came to have mitochondria in our cells. As you may remember from high school biology, mitochondria are the “power houses” of our cells.

Mitochondria take in glucose and oxygen and produce ATP molecules. ATP is the fuel for almost all biological processes in our body. Yet mitochondria were once free-living organisms, related to bacteria. Another organism, from the kingdom Archaea, swallowed a free-living mitochondrion. Instead of digesting it, they developed a symbiotic relationship. Technically, they form an endosymbiont (one organism living inside the other).

The resulting organisms – those whose cells have a defined nucleus – are called eukaryotes. We are eukaryotes. So are all animals, plants and fungi. When biologist Lynn Margulis proposed this “ancient bacterial assemblage” theory of eukaryotic cell structure in 1967, she was mocked, but it is now accepted science.

How often has this chance merger happened? All evidence is that this happened just once. In the entire history of our planet. Klaas calls this the greatest fluke of all time. Without this fluke, only microscopic life could exist. And this fluke could only happen once the even more amazing fluke of life happened.

Some people might invoke an intelligent designer. I see it as winning the biggest lottery ever. Perhaps we should spend our earnings more wisely? We often put ourselves down as a blight on the planet. Perhaps we are the best thing that ever happened?