[Animals] Why animals shrink explained with new evolution theory

[Angel of Death]

The mystery behind why Alaskan horses, cryptodiran turtles and island lizards shrunk over time may have been solved in a new study. The new theoretical research proposes that animal size over time depends on two key ecological factors: the intensity of direct competition for resources between species, and the risk of extinction from the environment. Using computer models simulating evolution, the study, published today (Thursday, 18 January) in communications biology, identifies why some species gradually get smaller, as indicated by fossil records. Dr Shovonlal Roy, an ecosystem modeller from the University of Reading who led the research, said: "Just like how we try to adapt to hot or cold weather depending on where we live, our research shows animal size can get bigger or smaller over long periods depending on the habitat or environment. "In places and times where there's lots of competition between different species for food and shelter, animal sizes often get smaller as the species spread out and adapt to the distribution of resources and competitors. For example, small horses that lived in Alaska during the Ice Age rapidly shrank due to changes in the climate and vegetation. “Where direct competition is less, sizes tend to get bigger, even though being really big and few in number can make animals more vulnerable to dying out – such as what happened with the dinosaurs. “Changes in ecological factors help explain why fossil records shows such confusing mixes of size evolution patterns, with some lineages shrinking over time and others growing."

https://www.reading.ac.uk/news/2024/Research-News/Why-animals-shrink-over-time-explained-with-new-evolution-theory