A History Of Life, Part I

“All living things have much in common, in their chemical composition, their germinal vesicles, their cellular structure, and their laws of growth and reproduction. (...) Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from one primordial form, into which life was first breathed.”
Charles Darwin, On the Origin of Species

Darwin’s view of descent by modification led him to the conclusion that there existed sometime in the very remote past an organism that is literally the universal common ancestor of us all. I’ve already written some articles about how life could have arisen from non-living matter, you may be interested in reading some of them. At some point in the remote past, life was somehow “breathed” into a primordial form. An entity appeared we’ll all agree was living. Once this entity had gained a foothold on life, it became the common ancestor to everything that has ever lived on the planet.

Exactly when this organism arose is uncertain, but we know a few things. We know that it has to be around 3.9 billion years ago, when the surface of the Earth was no longer been bombarded, and the crust of the planet had cooled sufficiently for liquid water to appear. Also, it had to be sometime before 3.5 billion years ago, which is the date of the oldest fossil cells that had been found so far. These oldest fossils are found in rocks in Western Australia. They’re actually quite advanced in their appearance, resembling certain kinds of modern bacteria, so most biologists assume that cells must have appeared even earlier than this.

Let’s review the characteristics of this first living thing. This organism was certainly a single cell. It had to have a membrane that created a compartment separating it from the rest of the world, allowing the accumulation of specialized organic molecules within. Among the organic compounds that made up this first organism there must had been complex polymers capable of catalyzing biochemical reactions, the kinds of reaction that would be necessary for this primitive cell to process materials, grow and divide.

The most specialized of these biological polymers must have been some kind of molecule that could not only catalyze reactions, but also serve as a template for making more of itself. In the earliest cells, this information probably was in some form of RNA. Later, some kind of genetic system was established in an RNA world. DNA then took over the role of storing and transmitting genetic information, while proteins took over the role of the functional molecule responsible for everything else the cell might do.

Without doubt, at this early period in time, the major effect of natural selection on this primitive organism was to refine its genetic system and to ensure that the different kinds of molecules within it would cooperate. There had to be some selection so that these different kinds of molecules (lipids, proteins, nucleic acids and sugars) would be able to specialize to do their own jobs in coordination with each other.

A Prokaryote World

By the time we get to the oldest fossils, evolution had established a recognizable cell, which is not too different from what might be a typical bacteria we find today. There’s a rich fossil record that continues from that period up to the present day. This fossil record makes a couple of things clear. First of all, it shows that when life did emerge, it emerged very rapidly and quickly filled the planet.

It also shows that only prokaryotic cells existed for about 1.5 billion years, until about 2 billion years ago. In other words, the more complex eukaryotic cells didn’t exist for quite some time. The early evolution of life was all in the context of prokaryotic cells. The fact that prokaryotic cells ruled the Earth for 1.5 billion years might sound boring, but it’s nothing of the sort. There were at least two major and exciting evolutionary events that occurred during this period.

The first was that the prokaryotes themselves split into two major lineages. We call these the bacteria and the archaea. The differences between bacteria and archaea are relatively subtle in the modern world. There are biochemical differences in their internal composition and other things. In fact, there are enormously more bacteria in the world today than there are archaea. The archaea largely have been relegated to very extreme environments. These are the ones that we find in extremely saline water, for example.

In a sense, archaea are not necessarily an important form of life to understand today, but they are very important for understanding the origin of eukaryotic cells, as we’ll see later.

The Scopes Trial, Part II

The initial attention attracted by the new Tennessee statute expanded into media frenzy, when six weeks after the statute became law, John Scopes was indicted for violating it. From its bizarre beginnings to its inconclusive ends, the Scopes trial was never a normal criminal prosecution.

Soon after Tennessee enacted the anti-evolution statute, the ACLU, from New York, offered to defend any Tennessee school teacher willing to challenge this law’s constitutionality in court. Dayton, a small town in East Tennessee, was in an economic crisis because its main industries had closed recently. Its civic leaders invited a local science teacher named John Scopes to accept the ACLU challenge as a means to publicize their town. Scopes agreed to the scheme even though he was not a biology teacher, and he had never violated the statute.

Scopes’ indictment made front page news around the world. He was never arrested. Indeed, he was never even threatened with jail. He was assured his job back the following year, because he was invited to challenge the law by the President of the school board himself. He actually spent most of the time from the indictment to the actual trial making media appearances and traveling.

Both sides in the larger controversy saw the pending trial as an opportunity to make their case to the general public. Both Bryan and the ACLU lawyers recognized this as an opportunity to make their case. It became a show trial and in the actual trial John Scopes actually disappeared. He never testified or major appearance.

On the defense side, was America’s most famous trial lawyer, noted religious skeptic, who was known for talking and writing about the dangers of religion, Clarence Darrow. He volunteered his services to lead a team of crack ACLU lawyers to defend Scopes. It was the only time in Clarence Darrow’s entire career that he volunteered his legal services. His goal was to debunk religious law-making and to promote individual liberty.

On the other side, Jennings Bryan, who was a lawyer but hadn’t practiced law in over 30 years, volunteered too. He volunteered to make the case against the teaching of evolution. He knew that the law, and not John Scopes, was on trial.

The media promoted this heavyweight bout as “The Trial of the Century”. It was just a simple misdemeanor trial with a potential fine of 500$!! However, Scopes wasn’t really on trial, the teaching of evolution and academic freedom was on trial. It was the first broadcasted trial in American history. It was covered by over 200 reporters. It was said at the end that more words had been telegraphed from the United States to England about this trial than any event that had previously occurred in American history.

The trial itself was anticlimactic, as each side made their very familiar arguments. These had been circling around for five years. Neither side disputed that Scopes had violated the law. When the judge refused to strike the statute as unconstitutional, Clarence Darrow asked the jury to convict Scopes so that they could appeal the judges of a higher court. If Scopes wasn’t convicted there couldn’t be an appeal and they couldn’t challenge the law.

They convicted Scopes and he was fined the minimum amount of 100$, which was paid on his behalf by one of the reporters. The trial’s most memorable event occurred near its end, when Clarence Darrow invited William Jennings Bryan to take the stand as a witness in defense of the anti-evolution statute. Bryan agreed to do so. Darrow asked questions about biblical literalism, such as: Was Jonas inside the whale for three days? Was Eve made with Adam’s rib? These questions made Bryan and the biblical account look foolish.

Following the trial, Scopes accepted a scholarship to study Geology at the University of Chicago, and became a petroleum engineer in Venezuela, and later managed an oil refinery. Bryan died in Dayton, less than a week after the trial, maybe because of the stress of the trial. His crusade, however, continued. Scopes’ conviction went on to appeal into Tennessee’s Supreme Court and it was overturned on a technicality.

The anti-evolution statute was declared constitutional, which foreclose any further appeal to the United States Supreme Court. Other States imposed similar laws. Indeed, if you look at the textbooks of the time, the theory of evolution is virtually non-existent. This is really an interesting case of willful ignorance, which repeated itself later in our history.