Why do animals shrink over time?

Why do animals shrink over time?

A new study sheds light on the factors that influence animal body size change over time and explains the inconsistencies between the fossil record. According to the website SiteTechDailyNew research suggests that animal size over time depends on two important ecological factors: the intensity of direct competition for resources between species and the risk of extinction from the environment.

A new study published on January 18 in the journal Communications Biology published, uses computer models to simulate evolution to show why some species have become smaller over time, as the fossil record shows.

According to the authors, their research shows that the size of animals over time can become larger or smaller depending on the habitat or environment.

In places and times where there is a lot of competition between different species for food and shelter, animal sizes often become smaller as species expand and animals adapt to the distribution of resources and competitors. For example, small horses that lived in Alaska during the Ice Age shrank rapidly due to changes in climate and vegetation.

According to the study paper, “Where there is less direct competition, sizes tend to be larger; Although the large and small numbers make the animals more vulnerable to death; Like what happened to the dinosaurs.”

Changing ecological factors help explain why the fossil record shows such a bewildering mix of size-evolutionary patterns, with some species becoming smaller and others larger over time.

The researchers conducted their study by challenging the inconsistencies in the fossil evidence presented in Cope’s Law. This law is named after Edward Cope, a 19th century paleontologist who, by examining the fossil record, found that some animal groups had evolved larger sizes over thousands and millions of years.

For example, the ancestors of early horses were small dog-sized animals that grew in size over time, eventually giving rise to modern horses. However, the fossil evidence shows conflicting trends where size decreased in some groups but not in others.

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Using computer simulations, the new study identifies three distinct evolutionary patterns of body size change that emerge under different conditions:

AGradual increase in size over time: This state occurs when the competition between species is determined more based on their relative body size than differences in habitat. For example, the size of several genera of marine animal species (e.g., invertebrates) gradually increased over millions of years.

Increase in size followed by extinction: Here the largest animals repeatedly become extinct, providing opportunities for other species to take their place and evolve larger bodies, and the cycle continues. Mass extinctions hit the apex predators the hardest. Very large mammals and birds, such as dinosaurs and large winged reptiles, were particularly vulnerable to extinction.

Gradual reduction in size over time: The simulations also predicted a violation of Cope’s law: species shrink over time. This situation occurs when competition is high and there is some overlap in habitat and resource use. As species evolve and each find their own distinct niche, they face evolutionary pressure to reduce body size. Reduced body size has been reported in previous studies in vertebrates, bony fishes, hawksbill turtles, Pleistocene Alaskan horses, and island lizards.

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