However, a new analysis of the fossil record reveals that the observed patterns—no evolutionary change punctuated by rapid biological innovation—do not match the patterns predicted if biological evolution accounts for life’s history and diversity. On the other hand, this pattern fits nicely within a creation model.
Typically within this sort of “hurry up and wait” pattern, new groups appear suddenly in the fossil record and then experience no evolutionary change (stasis). Recent work by an international team of evolutionary biologists seeks to explain this pattern using mathematical modeling.1
On the August 25 episode of Science News Flash, I discussed one recently discovered example of stasis in the fossil record. Paleontologists from the United States, Great Britain, and Germany generated 3-D reconstructions of two harvestmen (daddy longlegs) fossil specimens that date at around 305 million years in age. The researchers discovered that these ancient daddy longlegs possessed a surprisingly modern anatomy. In other words, these arachnids have not undergone evolutionary change for at least 300 million years and, in fact, may have been morphologically stagnant for up to 400 million years!
But the stasis of harvestmen anatomy is not an anomaly. It typifies the fossil record. The “hurry up and wait” pattern is counter-intuitive from an evolutionary perspective. Wouldn’t one expect gradual evolutionary change to be evident throughout the fossil record as new biological groups gradually emerge? This seems to be all the more the case given the rapid microevolutionary changes observed in nature, in some instances taking place over the span of a few generations.
These researchers examined changes in body size for a group of reptiles (squamates), birds, and mammals, making use of data from historical studies, the fossil record, and species comparative analyses.
Using 8,000 data points, the investigators detected a familiar pattern in the data. Even though short bursts of microevolution occur over a time interval of 1 million years, no directional evolutionary change is observed. Instead, the microevolutionary bursts merely represent fluctuations around an average value for body size. Once a microevolutionary change occurs, it is soon reversed by other microevolutionary events. To say it another way, microevolutionary changes appear to be constrained, explaining why stasis is a dominant feature of the fossil record.
It was also noted that over much larger time intervals (1 to 360 million years), evolutionary change is detected. But this change doesn’t accumulate gradually. Instead it happens suddenly, yielding what the team describes as a “blunderbuss” pattern.
The scientists surveyed a variety of mathematical models in hopes of finding one that would generate the same pattern as observed in the data. They learned that the best model couples rare bursts of evolution with bounded fluctuations for the parameters that describe the trait.
Biological traits are almost always perfectly suited to the environment and lifestyle of the organism. Microevolutionary changes that cause traits to deviate away from the optimum will reduce the fitness of the organism, thus, restricting the evolutionary process. If the microevolutionary changes do lead to increased fitness, then those changes are often constrained as well, because they almost always occur in a subpopulation and are localized to only a small part of the organism’s geographic range. Eventually these alterations will be off-set by microevolutionary changes that take place in other areas of the organism’s range. This explains why stasis occurs.
What researchers can’t explain, however, is what causes the innovative bursts in the fossil record.
The “Hurry Up and Wait” Pattern and the RTB Creation Model
The RTB creation model, on the other hand, explains the protracted periods of stasis followed by bursts of change. Accordingly, God created organisms with optimal designs. This activity would explain the sudden appearances in the fossil record. Because they are optimal, these organisms undergo limited change for the duration of their existence, accounting for stasis.
Even though I am skeptical about aspects of the evolutionary paradigm, microevolution (and speciation) is part of the RTB model. (Go here for a discussion of the different types of biological evolution.) The capacity for organisms to respond to changes in the environment through microevolution and speciation makes them robust, allowing them to survive in varying environments. In fact, microevolution and speciation are considered design features in the RTB model, providing a form of feedback regulation or control.
RTB’s model also maintains that microevolutionary changes are bounded. Even though organisms have the capacity to adapt to changing environments and other selective pressures, they cannot evolve in dramatic ways.
While patterns in the fossil record do not match the predictions made by the evolutionary paradigm, they are readily accommodated within RTB’s creation model.