Seriously, are the ID proponents at UD ever going to wonder why Gould and Eldredge remained persuaded that common descent occurred, and that “punctuated equibrium”, although contrary the uniformly incremental pattern that Darwin envisaged, was nonetheless consistent with Darwin’s proposed adaptive mechanism of heritable variation in reproductive success?
Because Darwin was indeed wrong about uniform change. Unlike us, he didn’t have computers with which to model the predicted output of his mechanism. Indeed he didn’t even know what the vector of heritability was. We do. Here’s a sample output from Eureqa, a program that uses Darwin’s proposed mechanism to “evolve” equations to fit data:
Look at the bottom left plot. It records the best-fitting equations as they evolve. On the vertical axis is the “error” in the evolving equations – the better the fit, the smaller the error. On the horizontal axis is the complexity. The program is set up so that complexity carries a penalty in terms of reproductive success but accuracy carries a reward. The most efficient equations – those that give best accuracy for least against complexity – are shown more green, while less efficient equations are shown more orange or red.
What happens over time is that as the equations evolve, there are discontinuities in the best error rate: note the step changes on the vertical dimensions. From time to time a small change in the equation will occasionally introduce a large improvement in accuracy. However, reductions in complexity tend to be more gradual. As a result, we see “punctuated equilibrium” – step changes in accuracy followed by gradual reductions in the equation’s complexity.
And the system is entirely Darwinian. Darwin couldn’t know that this is what his theory would actually predict. Of course he was right that adaptation would be incremental – and it is – but it is more incremental at the genomic level than at the phenotypic level. A small DNA change can result in quite a large phenotypic change. Again, Darwin could not know this. But, even phenotypic changes are gradual. The key point is that the rate of change is not uniform – indeed, uniform rates of change turn out to be very unlikely under the Darwinian mechanism. If one of the evolving equations in Eureqa gets a good “idea” (as in AVIDA) then there is very rapid change for a while as the population optimises itself to this newly available resource, followed by diminishing returns as a local maximum in accuracy is approached. Until something else happens – a novel mutation along yet another dimentions allows the population to exploit a whole new resource, following which, again, stasis is approached, and is maintained as long as the resource remains, and the population is not outcompeted by another lineage.
And that’s before we even consider that small populations will tend to adapt faster than larger ones – or die.
h/t to whoever introduced me to Eureqa! It’s brilliant, but I’ve forgotten who it was!