Editor’s Note: this is the third of an irregular but continuing series of columns written by Wil Taylor for the CVPost. It revisits Taylor’s popular six-part series on Charles Darwin, written last year shortly after the launch of this website. This article adds to Taylor’s interpretation for our readers of Darwin’s significance. The original “Deconstructing Darwin” series can be found at http://cvpost.org/wp-admin/post.php?post=10937&action=edit.
By Wil Taylor, for the Chippewa Valley Post
The Earth is about 4.5 billion years old. This well-established historical fact is still in “debate” if you read creationist web sites. But it was legitimately in debate for much of recorded human history.
Some Greek philosophers developed ideas about time. Most held to a cyclical concept of some sort, likely informed by the cyclical nature of days, phases of the moon, and seasons.
But it wasn’t until the run up to the Enlightenment that scholars thought to put an actual number on it.
Was there an authority on time? There most certainly was. There was a widely accepted estimate on the age of the Earth. And it was based on a source, THE source of unchallenged truth – The Bible. In 1650, the Archbishop of Armagh (Church of Ireland) James Ussher determined that the Earth was created at 6 pm on the evening of Oct. 22, 4004 BC.
This was based not just on the “begats” in the Book of Genesis. Those only get you so far. There are many gaps in the record after that point that required assumptions and correlations to other historical sources.
Stephen Jay Gould wrote an excellent essay on this topic entitled “Fall in the House of Ussher.” Gould reminds us that we should not judge too harshly conclusions from the past that sound ridiculous based on modern information (he calls this whiggish history). This was 17th century scholarship at its finest and this date appears in the margins of certain versions of the Bible.
Fossilized Evidence
However, that is not to say that scientists all clung to that age for very long in the face of evidence to the contrary, once discovered. And what were discovered were lots and lots of fossils. Through the 19th century, fossils – after having been fully embraced as the remains of living creatures the century before – were accumulating in great piles from all over. So scientists accepted that the Earth was old – they just had no idea how old.
Fossils also turned out to be useful. The person most credited with discovering this was a fellow named William Smith. Why was he interested? In addition to an apparently natural curiosity, he was a surveyor and canal builder in southwest England in the late 1700s, and this gave him exposure to lots and lots of rocks.
He observed, collected fossils, then tested, and finally demonstrated that he could trace one horizon of rocks across the surface of the land based on the fossils contained in that layer. Called correlation, this is highly useful if you are deciding which rocks make a better and easier path for a canal.
But Smith also discovered that fossils in layers above and below occurred in a predicable order. This came to be known as the Law of Faunal Succession, and it is a foundational principle of geology.
Smith focused more on the practical angle of this than on the historical element, producing the first large-scale geological map of the UK. It took others to expand upon the meaning of this for time.
What fossils had taught us was the concept of relative age, that is as opposed to absolute age. Since fossils are restricted to sedimentary rocks, which are deposited from flowing fluids (for example, a series of successive floods beside a river), they could serve as a chronicle of how the things living around or in those fluids changed over time.
Scientists were still operating under the assumption that the Bible was historically accurate, so some labored to reconcile the order of living (really dying) things with the Noachian Deluge (aka Noah’s flood). This legitimately scientific question was debated, studied, tested, and ultimately rejected in the 19th century. Modern creationists, though (at least the so-called young earth variety), still believe that fossils date from the Great Flood.
Even with all this, we were still no closer to an absolute age – a number.
Darwin’s Approach
Darwin had his crack at it in chapter 10 of On the Origin of Species.
He observed that there were about 74,000 feet of rocks that had been formed across England, which had originally been deposited as sediments. He estimated the number of years it would have taken for this to occur.
But Michael Ruse, in Darwinism Defended, comments that Darwin’s calculations “remind us of the popular engineer’s way of finding a solution: one thinks of a number, doubles it, then takes half to get the solution.”
So we can ask why Darwin would devote time to something he clearly had no clue how to approach?
He needed it.
He needed it badly.
He needed it badly for his mechanism of evolutionary change to operate. The mechanism Darwin presented in On the Origin of Species – natural selection – was slow. It needed immense time in order to create the diversity he saw, particularly the diversity that had poured into Europe from collectors sending back new specimens from all over the world. This was a time when people began to realize that we were previously unaware of just how many kinds of organisms the planet held.
Now, at the end of the 19th century the dominant scientific idea for where this diversity came from was still The Doctrine of Special Creation. But that was also beginning to unravel as it was realized that organisms must have gone extinct, which did not fit the model of Special Creation at all.
Why would Providence create things in a perfect world, only to destroy them? The age was ripe for a better explanation. And the idea of organisms actually changing over time was fairly new and provocative. Darwin’s publication of On the Origin of Species laid out the argument for a shared ancestry in such a convincing and thorough way that it marked the turning point for the abandonment of Special Creation.
But time was still a problem.
Narrowing the Range
In the words of Bill Bryson, in A Short History of Nearly Everything:
“. . . by the close of the 19th century, depending on which text you consulted, you could learn that the number of years that stood between us and the dawn of complex life in the Cambrian Period was 3 million, 18 million, 600 million, 794 million, or 2.4 billion, or some other number within that range.”
There was one figure of note who had more authority than anyone else. William Thomson, later Lord Kelvin. Of the many accomplishments of this giant of physics, computing the age of the Earth was among the most public.
Based on his work with thermodynamics, he presumed the Earth started as a red hot body, and then cooled to its present state. In the absence of any known mechanism of renewing the heat, he calculated that the Earth could not be older than 20-40 million years. And in this, he was a skeptic of Darwin’s mechanism of natural selection.
Within his lifetime, radioactivity was discovered, which provided that source of renewed heat.
Radioactivity also was the basis of the first reliable method of calculating absolute ages of rocks. Called radiometric dating (of which carbon dating is one – but one with a limit of about 50,000 years in most cases) it uses the transformation of radioactive isotopes from their unstable to their stable daughter products as a clock, and is extremely powerful and accurate.
So we finally have that date that I opened with – 4.5 billion years. More precisely, 4.54 billion years, ± 50,000,000 years. This immensity of time is impossible to fathom for an organism that rarely sees a full century. Despite this, we can consider ourselves to be rather clever primates that we can arrive at such an accurate date.
And finally: A man who dares to waste one hour of time, has not discovered the value of life – Charles Darwin
Wil Taylor is professor and chair of the Biology Department at the University of Wisconsin-Eau Claire.