A trio of biologists and environmental scientists, two at the University of Friborg and the third at the Swiss Institute of Bioinformatics, found that fully aquatic mammals, such as whales and porpoises, less likely to evolve back into land animals. In their study, reported in Proceedings of the Royal Society BBM Farina, S. Faurby and D. Silvestro conducted a phylogenetic analysis of over 5,000 mammalian species.
Early research showed that life began in water and matured in the oceans. Then, between 350 and 400 million years ago, other creatures began to use their fins to move around on land. Over time, these appendages changed to better suit life on land, eventually allowing some creatures to become fully terrestrial. But something strange happened about 250 million years ago. Some of those land creatures began to trickle back into the sea, and over time, developed ways of living there. In this new effort, researchers are wondering if it is possible that the species that returned to the sea will return to the land animals.
The task involved dividing thousands of species into four main mammal groups; those who live only on land, land animals with some water abilities, sea animals with some terrestrial abilities, and those who live only in the sea. The team then examined the relationships between species in different branches that shared common ancestry. By comparing their characteristics, they found that the probability of any fully sea creatures evolving to survive on land was almost zero.
Taking a closer look, the researchers found that there is a threshold that, once passed, prevents a marine species from evolving back into a terrestrial species. They noticed that when land animals go to the sea, they undergo major changes in their body, such as increasing in size, which helps retain the heat of the cold water. They also noted that most of the creatures that returned to the sea became carnivores. The study included only mammals; thus, there may be differences for other types of creatures.
BM Farina et al, Dollo meets Bergmann: morphological evolution of secondary aquatic mammals, Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2023.1099
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Citation: Phylogenetic analysis suggests that fully aquatic mammals are unlikely to evolve back into terrestrial creatures (2023, July 18) retrieved 18 July 2023 from https://phys.org/ news/2023-07-phylogenetic-analysis-fully-aquatic-mammals. html
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