Darwin’s gradual process theory explained in new research

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Abrupt changes in animal evolution – short periods of time during which an organism rapidly changes size or shape – have long been a challenge for theorists, including Darwin. Now, a recently published research paper supports the idea that even these abrupt changes are underpinned by a gradual directional process of successive incremental changes, as assumed by Darwin’s theory of evolution.

Posted in Nature Communication Now, evolutionary biologists from the University of Reading are proposing a new statistical model that seeks to explain these sudden changes and long periods of stasis that have been observed in the evolutionary history of some species.

The team led by Professor Mark Pagel and colleagues Dr Ciara O’Donovan and Dr Andrew Meade developed a statistical model that reconstructed changes in body size that occurred throughout the 170 million years. years of history of more than 2800 species of mammals.

The authors found that despite the existence of periods for some mammals in which abrupt changes in size occur, these events can be understood as “normal” changes that build on the natural variability that evolution regularly adds. to natural populations.

Professor Mark Pagel, professor of evolutionary biology at the University of Reading and lead author of the paper, said:

“Our statistical model provides a basis to accommodate what was previously a thorn in the side of theorists such as Darwin.

“Darwin’s theory of evolution by natural selection predicts gradual and progressive changes in organisms occurring over very long periods of time. But the fossil record frequently shows very abrupt changes in the sizes, shapes, colors and other characteristics of organisms, and these have been used for at least fifty years to challenge Darwinian orthodoxy.

“We show in this paper that even these abrupt changes are easily explained as instances of so-called ‘directional selection’ – when natural selection pulls a strong line in one direction. No special extra-Darwinian mechanism is required.

Many of these abrupt changes occurred around 60 to 70 million years ago, a period that saw the rise of many different mammal groups from earlier forms. For example, over a period of 100,000 years, a small early grazing animal (Conacodon entocone), ancestral to today’s modern cows, antelopes, and giraffes, grew more than 70 times its size. More recently, baleen whales (e.g., humpback whales, blue whales, and sperm whales) grew more than 100 times in size from a small dolphin-like ancestor in the same time frame ( ~7 million years) that separates modern humans from their common. ancestor with chimpanzees.


Examine sudden evolutionary change


More information:

The general statistical model shows that macroevolutionary patterns and processes are consistent with Darwinian gradualism, Nature Communication (2022). DOI: 10.1038/s41467-022-28595-z

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