Researchers have long observed that evolutionary rates seem to accelerate over shorter time frames, suggesting that ‘younger’ groups of organisms evolve faster. However, a new study published in PLOS Computational Biology proposes a surprising explanation: statistical ‘noise’ is responsible for this perceived pattern. By employing a novel statistical approach, the authors demonstrate that this hyperbolic trend is actually an anomaly, not a true reflection of evolutionary processes. This finding challenges the long-held assumptions about the dynamics of macroevolution and microevolution.
Unraveling the Paradox
One of the longstanding concerns that researchers have tried to understand is why evolutionary rates seem to speed up in short time frames. More generally, this interesting organisation has suggested the idea that in some sense, ‘younger’ groups of organisms in evolutionary terms – those formed since a common ancestor began to diversify into separate species – show rates of speciation, extinction and other changes faster than their older counterparts. The bigger question: what snafu causes this to happen?
Historically, explanations have invoked colonization of new habitats, catastrophic events (such as an asteroid impact that wiped out the dinosaurs), or a model where species evolve to some ‘optimal’ trait value beyond which further selection leads to stagnating evolution. However, a new study by Brian C. O’Meara and Jeremy M. Beaulieu turns the conventional wisdom on its head with another suggestion: statistical ‘noise’.
Exposing the Anomaly
Follow-up analyses by the authors of the study, published in PLOS Computational Biology, revealed this decades-old pattern to be further true than even de Wit and Laland had hoped. USING SOUND SCIENCE Ho and Phillips, analyzing everything from molecular biology to geology, concluded that acceleration of evolution over shorter time scales is illusory rather than reflective of changes in the underlying process.
In truth evolutionary rates do not increase over shorter time frames, as one might infer from the misleading hyperbolic pattern inadvertently induced by a time-independent noise that is typically ignored as inconsequential, which ‘by employing a novel statistical approach’ they found to be ‘just not true,’ explain the authors. This, more simply put means that the data shows young small groups of organisms evolve quickly not because its somehow an advantage to be young and small, but just because things like this are multiply unlucky.
Redefining Our Understanding
This study has huge implications as it changes the way we have assumed evolution works over time scales. The authors write, ‘Evolution occurring on entirely different time scales is much less probable than actual oscillations in these quantities.
Our findings highlight the need to consider and correct for some of the biases and errors that are present in our interpretations of biodiversity patterns, both on short and long geological time scales. As the authors put it, “Our results are potentially disappointing: a pattern that might have inspired a thousand papers with really fascinating biological hypotheses can be caught as an artifact. But in fact this is progress — we have a story explaining a regularity that we observe around the world.
In doing so, the study takes account of the idiosyncratic role of statistical noise in shaping our perceptions of rates of evolution, and provides a more precise basis for understanding—and ultimately predicting—this fundamental aspect of the history and future of all life on Earth.
