Bursty speciation


One of the typical challenges to traditional evolution is the gaps that are observed in the fossil record. We find many fossils of a given species. But we rarely or never find the fossil record of the transitions that lead from one species to another – like from dinosaurs to birds. There are possibly some feathered dinosaur fossils, but not enough for us to be able to say that the fossil record records the transition.

Generally the explanation for this is to point out that the chances that an individual organism is going to leave a fossil behind are pretty small. So if there’s a small transitional population of organisms that represent the process of a species transforming to another then the chances of catching that in the fossil record are that much smaller. Thus the fact that we don’t see the transitions is a function of sampling and not something that disproves the basic ideas of evolution.

Except it sort of does. Traditional evolutionary thought would have us think that there are a relatively smooth rate of biological mutations as one generation of organisms leads to another. That’s what we’ve been able to observe today in short lived species like fruit flies or various bacterial strains. And if the evolutionary development is made up of small steady perturbations, then we should be seeing more transitional fossils than we are.

So there’s a problem.

There’s a new suggestion that takes the old idea used to explain the former suggestion about why we don’t see the transitions and looks into more closely. I think of it as the model of bursty speciation – where BIG changes happen quickly, and then the regular rate of small changes resume.

There’s a new paper that argues, from a computational view, that this might be exactly what happens:

“‘What we’ve shown is that speciation is about happy accidents — rare events that happen in the environment that cause a species to speciate,’ says Pagel. These events could include a mountain range being thrust up or a shift in climate, he says.

The team’s findings might stir things up in the world of evolutionary biology. ‘It really goes against the grain because most of us have this Darwinian view of speciation,’ says Pagel. ‘What we’re saying is that to think about natural selection as the cause of speciation is perhaps wrong.’

Mike Benton, a palaeontologist at the University of Bristol, UK, agrees that the work might ruffle a few feathers, adding that it could also shift attention to how groups of species evolve, rather than the minutiae of competition or predation effects that affect a single species. Where speciation is concerned, at least, ‘maybe all of this squabbling in the undergrowth is quite irrelevant’.”

Read the full article here.

Bears watching I would imagine.

The Author

Episcopal bishop, dad, astronomer, erstwhile dancer...

1 Comment

  1. John Borrego says

    “I think of it as the model of bursty speciation – where BIG changes happen quickly, and then the regular rate of small changes resume.”
    How is this different from Eldredge and Gould’s “punctuated equilibrium”?

Comments are closed.