Scientists have studied the fossil remains of ancient mammals that lived in the Eocene period, about 53 million years ago, during one of the warming of the Earth’s climate — the second Eocene thermal maximum (ETM-2). During ETM-2, the average temperature on the planet increased by 3 °C. Previous research on the Paleocene-Eocene thermal maximum, which was for two million years before ETM-2, has shown that the body size of mammals decreases under climate warming, and scientists decided to test the data on another material.
Scientists have studied the remains of the ancestors of modern horses, artiodactyls, and primates — three ungulate the size of a cat or rabbit, and one ancient predatory Primate similar to a lemur. The researchers studied the fossil teeth of these species are related to different stages of ETM-2 to see how animals have evolved and changed over warming. For this they used the knowledge about the correlation of teeth size with body weight.
It turned out that two — Arenahippus pernix (horse) and Diacodexis metsiacus (cloven-hoofed), lost in the mass of approximately 15%. The other two species (hoofed and Primate) also decreased but not to the same extent.
As scientists say, to explain the reduction of body size during warming first of all you need to remember about Bergman’s rule, according to which, the colder the climate in which animals live, so they are larger. Animals that live in the warmer latitudes, the ratio of body surface to weight more than those who live to the North, and because they better give excess heat to the environment.
As they say the paleontologists, the decrease in body mass in response to climate warming can be observed in modern animals, for example sheep, deer, and squirrels. The results of a study of changes in body weight in the Eocene only confirm existing data, and thus, as scientists believe, “degeneration” is waiting for mammals and in the near future.
The study described in the journal Science Advances.