The amazing change in corn over the centuries, from grass-like Teosinte to a more familiar, modern variety.
Happy belated
Darwin Day, though Charles Darwin's birthday and therefore his
namesake day was actually February 12, 1809! Despite an ongoing hostility toward science in general and biology specifically from the usual suspects, evolution is under little threat in the west as the best explanation, hands down, for the dazzling biodiversity seen on the living Earth today. Darwin wasn't the first to notice familiarity in different creatures or to consider forces driving common descent. But he was among the first to assemble a large body of empirical evidence gathered over decades of collecting to make the case for what we know today as evolution. A body that has been judged to be the most robust early on and still stands today as one of the best scientific presentations ever made.
On the Origin of the Species published in 1859, starts with a simple, irrefutable,
persuasive premise:
When we look to the individuals of the same variety or sub-variety of our older cultivated plants and animals, one of the first points which strikes us, is, that they generally differ much more from each other, than do the individuals of any one species or variety in a state of nature. When we reflect on the vast diversity of the plants and animals which have been cultivated, and which have varied during all ages under the most different climates and treatment, I think we are driven to conclude that this greater variability is simply due to our domestic productions having been raised under conditions of life not so uniform as, and somewhat different from, those to which the parent-species have been exposed under nature.
Quite simply, if we can turn teosinte into 12-inch golden corncobs in just a thousand years or so, why can't nature do the same to the form and function of other living things over millions? Once offered up it seems so obvious, the only real test for Darwin's thesis is if the Earth has been around with living things for the requisite millions of years.
In the years following Origin's, scientists would learn much more about developmental and comparative biology, heredity was first inferred and then understood, many, many transitional fossils would be found including ancestors and close relatives of anatomically modern humans, radiometric dating was established and just as quickly refined a number of key transitional lineages into perfect chronological lines of progression. By then we had the smoking gun. More recently, thanks to molecular biology, we practically have video of evolution pulling the trigger.
Every one of those lines of evidence solidly supports common descent. More on that and some thoughts on the opposition to the underlying theory of all biology below the fold.
It's important to accept that common descent is pretty much perceived as an empirical fact in science, as easily inferred through a range of observations as any other. It's as obvious as the origin of thousands of craters on the moon or the meteorite craters and volcano remnants on Earth, in that we see lots of them frozen in time and occasionally see actual examples of how it happens in specific cases from start to finish. Common descent is at least as well accepted in biology as the results of genetic analysis are accepted in paternity and criminal matters. The theoretical part of evolution, the part that Darwin so ably addressed, is how that might happen. How does a land animal morph into a blue-whale or an extinct, relatively heavy dino into a familiar, extant eagle?
The stages are fascinating in those lineages and the same for others. But they're just academic without a mechanism which allows some plasticity in form and function that can accumulate over many generations. Darwin's main answer to that in 1859 is usually referred to as natural selection and is built on several testable bullet points, for example:
- Deep time: it was strongly suspected by 1859 that the Earth and living things on it had existed for millions and millions of years. We have since tested this and now know the Earth is ~4.54 billion years old depending on what you define as Earth, and that living things have been on it for over three billion-years.
- We know that in many cases more offspring are created than the environment can carry through to adulthood. This leads to inevitable, ruthless competition for resources and mates. An individual with a desirable feature or features is therefore at a selective advantage to survive and leave descendants.
- Heredity: we suspected by the 19th century -- and have since come to appreciate exactly how -- that some of these traits can develop and be passed on to descendents. If they are continuously selected for over many generations, we can safely infer they would become common in a larger population over time as in the case of artificial selection that Darwin started Origin's off with.
- Explanation! Changes in form and function, what biologists might call morphology, occur over time and --- this is key to understand -- they are cumulative as each new generation is starting basically from the endpoint of the last one.
Origin's was so persuasive that, within 10 years of publication, the general reaction among biologists world-wide was along the lines of, "Yes! That's how it has to work. It's so obvious, I can't believe I didn't think of it first!" But back in Darwin's day and into the modern era, the big concern wasn't just the science. Pointed, well thought out criticism is fine for science, it's better than fine, it is essential. Criticism is the immune system of science that saves it from collapsing into an unrecognizable, pseudo-scientific puddle of slimy woo ready to fill in and backstop any ideology, species of politics, or wishful thought on demand.
One of the main concerns of the day was a real theological conundrum: without a literal Garden of Eden and Fall of Man, there would be no original sin and no need to punish all future humans for the defiance of Adam and Eve. The burden for suffering and evil in the world would then shift away from humans to God, and could even question the point of salvation through Christ. Something similar works against any Old-Earth interpretation in related faiths.
You won't hear much about this problem these days, though. It was addressed decades ago in almost every Christian denomination as well as related religions. Most, including the Roman Catholic Church, have come to an accommodation which allows followers to accept both deep time and common descent with minor, purely theological additions. The remaining theological push-back in the US came almost entirely from a version of fundamentalism associated more closely with a few scattered, mostly rural regions at the turn of the 19th century. It simmered under the radar for years, breaking out now and then in places like the Scopes Monkey Trial.
What we call 'scientific creationism' (And its offspring Intelligent Design Creationism) didn't really get going in the US until the late 1960s, when a strong national push for science, begun in the aftermath of Sputnik and the Space Race during the late 1950s, seeped into local schools and homes where closely related, various forms of fundamentalist Christianity were still observed. A rather nasty, informal bargain was struck between a few very wealthy clans who detest public schools, arguably in part because of the property and other taxes they pay to support them, and local working-class fundamentalist Christians who, sad to say, benefit economically and whose children benefit educationally from the public school system. Similar wedges have been cultivated for similar reasons; school prayer, sex education, LBGT teachers, public sector unions, and to some degree the home-school movement. In other words, these days it's not just science, it's also about the dollars, always the dollars.
It's hard to say how that will end or if it ever will. As long as enough money is behind it, creationism and other anti-science forces will exist in some form or another. But in terms of science, it's completely over. The evidence for evolution has grown so vast that a budding researcher can pick one tiny line of work and spend his or her entire professional life studying it from the perspective of a dozen or more sub-disciplines. All chiming in, highlighting newer, unique notes in the elegant, stirring and so often savage history of the evolution of life on Earth.
So last week we honored Darwin, who fair and square, found his own share of fame and fortune in the only real lasting currency accepted in science through all the years since: He was right.