A long-held theory involving the quickened pace of evolution over short time frames could be explained by an “anomaly” revealed by researchers in a new study.
This idea tends to hold that organisms that have existed for relatively shorter evolutionary periods seem to display greater rates of body size evolution, speciation, and even higher extinction rates, than those which have persisted over much longer periods. However, new biological research suggests that statistical noise could account for such observations, which have held their place in evolutionary theory now for decades.
The findings, published in PLOS Computational Biology argues that a more likely explanation lies in the statistical noise arising from data scientists have relied on for such observations.
Linking Micro- and Macroevolution
The apparent fact that there are differences in evolutionary processes with relation to the time scales over which they occur, giving rise to concepts of microevolution and macroevolution, has led to questions of whether a new, more refined theory that links the two might be a necessity.
However, more broadly, scientists have simply wondered why the differences between shorter term evolutionary periods and those of evolutionarily longer organisms appears to occur.
According to new research by Brian C. O’Meara, a professor in the Department of Ecology and Evolutionary Biology at the University of Tennessee, and Jeremy M. Beaulieu, an associate professor of in the Department of Biological Sciences at the University of Arkansas, taking a statistical approach toward this longstanding problem in evolution studies may have finally yielded an answer: what they characterize as “time-independent noise.”
“[W]e found that this time-independent noise, often overlooked as inconsequential, creates a misleading hyperbolic pattern,” O’Meara and Beaulieu write in their paper, “making it seem like evolutionary rates increase over shorter time frames when, in fact, they do not.”
“In other words, our findings suggest that smaller, younger clades [groups with common ancestors] appear to evolve faster not due to intrinsic properties but because of statistical noise,” the researchers write.
An Anomaly in Evolution
The implications, based on a hybrid approach that unites math and biology with statistics, suggests that the apparent hyperbolic pattern that arises from the data is simply an anomaly, given that the emergent pattern does not actually account for factors that include how all species are defined by specific traits, as well as the ways that variation in those traits remains apparent.
Given such circumstances, the notion that evolution occurs in so vastly different ways along different timescales seems counterintuitive, and according to O’Meara and Beaulieu, that’s probably because it isn’t a correct interpretation of the phenomena at hand.
Instead, the researchers argue that biases and errors in the way past interpretations have grappled with the apparent divide between macroevolution and microevolution is the more likely explanation for this lingering evolutionary mystery.
“Our results might be seen as upsetting,” O’Meara and Beaulieu write, noting that what they propose may be a misinterpretation arising from statistical noise could have “launched a thousand papers with really interesting biological hypotheses” but which now “can be explained as an artifact.”
Nonetheless, the pair say that rather than a step back, resolving this lingering evolutionary conundrum on far simpler terms than past approaches have argued is a sign of progress.
Ultimately, they argue that their new research has “explained a common pattern we see in the world. Biology is rich in mysteries: actually answering one lets us move on to the next.”
“There are still many questions about biological rates,” the authors conclude, though adding that “the current paradigm of plotting rates against time should probably end.”
The new paper, “Noise leads to the perceived increase in evolutionary rates over short time scales,” was published on 13 September 2024 in PLOS Computational Biology.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.