Hypothetically speaking...

In the first of a series of articles that pays tribute to the great theories, and the great minds behind them, Laboratory News explores Charles Darwin and his theory of evolution by natural selection

Science is only as good as the theories that it tests. With out a coherent hypothesis to draw together discovery, scientists would simply be the guardians of a collection of abstract facts.

However, theories that comprehensively explain all the evidence before them, and of course stand the test of evidence that will follow, are rare events indeed. The history of science is littered with the tattered remains of theories that crumbled under the pressure of advancing discovery.

But when one does come along that truly explains all that it sets out to, it can be a revelation. Even in their simplest forms these theories allow the misty secrets of the universe to be cleared – even if just a little – to give us an insight into what we are and what we are doing here.

But what goes into a theory? Do they all arise in moments of inspiration that cause obsessive scientists to leap from their baths shouting eureka, or do they simmer away during decades of toil before slowly becoming accepted?

In the case of the theory of evolution by natural selection, it was certainly the latter. The idea that species evolve when environmental pressures select out small variations in individuals that give them some kind of advantage, making them more likely to survive and reproduce – survival of the fittest – is now taken for granted by many. But it was not long ago that the idea was simply unthinkable.

Darwin: The accidental hero
 
As world changing theories go, Darwin’s ideas on the origin of species are one of the most influential and controversial that science has to offer.

It is hard to image the scientific climate in which Darwin formulated his ideas. Science was largely conducted by priests and pastors with the aim of confirming the teachings of the bible. Indeed, after failing medical school Darwin himself was training to become a member of the clergy.

However, Darwin did not turn out to be a hardworking student; he was less likely to be studying the bible than hunting for beetles. After developing a keen interest in natural history during his time avoiding lectures and sermons, he began to plan a trip that would eventually lead to the conclusion that humans, far from being granted a special place in God’s creation, were in fact just another species among many that had evolved from the most basic primordial building blocks of life.

After reading about the travels of other great naturalists of the time Darwin became convinced that the only way to unlock the secrets of nature was to leave the shores of England. After a few false starts, Darwin traveled to his family home in Shropshire where he found a letter from a tutor that he had befriended at Cambridge University, John Stevens Henslow. The letter, to Darwin’s surprise, invited him to take a trip around the world.

The invitation was to take up a position as captain’s companion on board HMS Beagle, a mapping ship bound for South America. This rather unusual position grew out of the fact that captains did not socialise with their crews, and the solitude was thought to be psychologically damaging. However, Darwin only agreed if he could also act as the ships naturalist.

As soon as the Beagle set sail from Plymouth on December 7th 1831, Darwin became terribly sea sick, despite five years and many thousands of miles on the Beagle he would never find his sea legs. In February 1832 the ship reached the coast of Salvador, and for the next three years Darwin would spend most of his time on land. In Brazil he lived in the jungle and it was here that he started recording and collecting everything he encountered, filling his sample jars with hundreds of new creatures.

Surprisingly it was not the biology of these new collections that sparked Darwin’s theory, but the geology of the landscapes that he encountered. After reading Principles of Geology by English geologist Charles Lyell, he became aware that the planet was formed by local changes, in a state of perpetual flux for an unimaginable span of time.

Of course, it is the idea of local environment changes that in part drives the theory of evolution that Darwin would later formulate. 

There has been much made of the fact that Darwin didn’t so much come up with evolution, but rather developed the idea. Well, in essence this is true, as it is of most scientific theories. In this case the original idea of evolution was brought up, not by a scientific rival of Darwin, but his own grandfather. Erasmus Darwin, a doctor who was also a botanist and best selling poet, had argued that all living things had originally derived from microorganisms.  

However, it was the method by which living things evolve that was Darwin’s great contribution, and it was a visit to the Beagles next destination that would give him the vital clues for his theory.

After leaving South America, the ship arrived at the Galápagos Islands. In his journal Darwin remarked that “the natural history of this archipelago is very remarkable, it seems to be a little world within its self.” It wasn’t until he was to return to England and study his specimens in detail that he would realise the significance of this collection of islands.                                                   Blue footed boobies are
                                                    only found on the Galapagos Islands

The Beagle returned from its round the world trip in October 1836 and Darwin returned to his home to work on his emerging theory. This he did in secret as he knew that any ideas suggesting the influence of nature over religion were still considered heresy. A year later, in a private notebook, he sketched out a tree of life tracing the evolution of one species into another for the first time. Darwin found his own idea terrifying, and his health would suffer as a result of the potential controversy.

As the years past and Darwin remained silent, other ideas on the natural laws that governed life began to be published. But still, Darwin delayed publishing his findings, instead studying the biology of Barnacles.

In fact it was the theories of a scientist who was himself inspired by Darwin that would finally convince him to release his ideas. Alfred Russel Wallace had similar ideas about evolution and had written to Darwin – now a well respected naturalist for work in other areas - explaining them. Darwin decided that now was the time to release his theory, but was determined not to rob Wallace of any credit. He arranged for the Linnaean Society to hear both papers at the same time. June 30th 1858 would see the end of twenty years of research and anxiety. Darwin’s ideas were now public.

Soon after he expanded on this initial explanation and published On the Origin of Species by Means of Natural Selection. One of the reasons that the book became so well known and eventually accepted is the nature in which it was written. It is defensive from the outset, addressing the inevitable objections that would arise from other, more conventional scientists, before they could be made.

Despite this, most reviewers of the time dismissed it as blasphemy, claming the theory to be “an abuse of science”. However, by the 1870’s almost all serious scientists in Britain had accepted evolution, and during the 20th Century the evidence for the gradual evolution of species by natural selection has been truly been recognised.


Darwin's privately sketched tree of life

As a theory it has stood the test of time. But it did not come easily. A trip around the world, twenty years of hard examination of evidence, personal confrontation, risk of scientific obscurity and damage to health. Natural selection as a theory was not a eureka moment, but was built up on a base of previous inspirational ideas, hard work and a fiercely inquisitive nature. As a theory it assumed a great deal about the age of the Earth and the nature of heritable material, but all of these assumptions have survived the onslaught of study and evidence that followed, and still follow to this day.

By Phil Prime, Assistant Editor, Laboratory News