Two Versions of Evolution?
By Jake Ramgren
When I say the phrase "do the dishes" what vision appears in your mind? Do you picture yourself cleaning dishes with a soap and sponge? Or do you imagine yourself loading a dishwasher to clean all the dishes at once?
Charles Darwin probably did the former. And, in a way, so did his theory of evolution.
In the latter half of the 19th Century, Charles Darwin's version of evolution (natural selection producing new forms over many years) dominated evolutionary thinking. That's not to say everyone agreed with the theory or the mechanism, but biologists were generally convinced that evolution worked gradually, using slow processes and miniscule changes over time. A process similar to, say, doing the dishes one at a time by hand.
The big problem with his theory was well-known even by those who believed his theory: the fossil record had almost no transitional forms. There were no fossils that reflected a gradual change of one type of animal into another. Species in the fossil record appeared in one place, lasted for a few million years, and then disappeared. Darwin's response to this challenge was simple: we haven't found them yet. In his defense, the fossil record was pretty weak compared to today. So, one could give him a pass simply for living in the times he was in. But as the years passed, paleontologists continued to struggle reconciling Darwinian evolution with the fossil record.
So, by the second half of the 20th Century, a new perspective had taken root. Stephen Jay Gould had proposed his alternative theory: punctuated equilibrium. Gould believed evolution happened in leaps, with millions of years of stability (no evolution) in between. Gould's idea is essentially the dishwasher version of evolution: the dishes do not get cleaned gradually and one at a time, but periodically, and all at once. In his theory, no evolution happens for millions of years, and then suddenly lots of evolution happens in a big spurt, and new organisms appear almost immediately, with no geological time for transitional forms to be fossilized.
Stephen Jay Gould (1941-2002) Photo credit: biblogteca.org
Gould proposed this as an alternative to Darwin's version of evolution to account for the long periods of stasis (a.k.a. no change) in the fossil record. This created quite the stir among evolutionary scientists, with a simple pattern developing among scientists as to who prefers which theory. Geneticists stuck with Gradualism while paleontologists favored Gould's Punctuated Equilibrium. This disagreement culminated in a dramatic debate at the "Macroevolution conference" in 1980 at the Chicago Field Museum. This meeting essentially played out as a showdown between geneticists and paleontologists. The problem was that genetically, it looked like evolution occurred gradually. But the fossil record seemed to reflect a lack of gradual transitions.
A 1980 paper from The Houston Chronicle describes the debate well. It even references creationists of the day using this conflict to attempt to portray evolution as a theory in crisis. Here is the excerpt:
Exactly how evolution happened is now a matter of great controversy among biologists. Although the debate has been under way for several years, it reached a crescendo last month, as some 150 scientists specializing in evolutionary studies met for four days in Chicago’s Field Museum of Natural History to thrash out a variety of new hypotheses that are challenging older ideas. The meeting, which was closed to all but a few observers, included nearly all the leading evolutionists in paleontology, population genetics, taxonomy and related fields. No clear resolution of the controversies was in sight. This fact has often been exploited by religious fundamentalists who misunderstood it to suggest weakness in the fact of evolution rather than the perceived mechanism. Actually, it reflects significant progress toward a much deeper understanding of the history of life on Earth.
The entire debate is too much to cover here, but the newspaper outlines a couple particular points of disagreement. For example, geneticists pointed to the fossil record of horse evolution, which seems to indicate a gradual chain of evolution from an extinct ancestor to today's modern horse, as evidence of Gradualism. But the paleontologists argued that each fossil in the chain appeared in the fossil record suddenly, with no fossils showing transition between them. "Instead of gradual change" the Chronicle wrote, "fossils of each intermediate species appear fully distinct, persist unchanged, and then become extinct. Transitional forms are unknown."
The scientists did decide on a resolution, and it is one that is accepted by scientists of all backgrounds today. It goes like this: in the present day, species change and adapt gradually, similar to how Darwin envisioned. But under certain circumstances, dramatic evolution can occur suddenly, which results in a fossil record full of organisms that appear and disappear largely unchanged. Here is what one scientist wrote after the conference:
Consequently, Darwin's meaning of the term "gradualism" was certainly compatible with the sudden appearance of forms in the fossil record-even for a very complete fossil record. Hence, the issue is not adaptive gradualism, but rather whether adaptive gradualism occurs continuously and slowly over long periods of geological time as the quote of Lewin given above implies.
(Futuyma, D. J., et al. “Macroevolution Conference.” Science, vol. 211, no. 4484, 1981, pp. 770–74. JSTOR, http://www.jstor.org/stable/1685999.)
The conclusions of academia roughly falls in line with this resolution. Evolution occurs gradually all the time and suddenly every once in a long while.
How do creationists interpret this internal conflict behind enemy lines? For one, it is probably not wise to use this controversy as an argument against evolution, since these scientists have already thought about this issue very deeply and debated it amongst themselves! It is safe to say the controversy is in the rear-view mirror.
But what should creationists think of the fossil record and genetic data? Well, creationists are not operating on the timeline Darwin accepted, and we do not accept that all organisms evolved through descent with modification from a common ancestor. But we do think there was at least one dramatic "punctuation" in the history of the world: after the flood of Noah! In our model, as animals leave the Ark, they quickly diversify and adapt to environments outside of the Ark. This can be seen as "rapid evolution," which is in a way very similar to Gould's idea. But the mechanisms creationists accept as drivers of rapid change are often genetic, and occurring in nature all the time. If God designed organisms with the ability to adapt to environments, then creationists too accept a dual explanation for change. We accept adaptations and rapid speciation, while also recognizing that at one point in world history, conditions caused a much more dramatic period of rapid "evolution." Unlike Gould and everyone else in Chicago in 1980, however, creationists believe these evolutionary changes only happened within created kinds.
Though this debate has long been settled, it is worthwhile to remember that science is never squeaky clean.
Something to think about while you do the dishes.
