The Evolution of Mammals and How They Adapted to Live in the Sea
Student Summary by Jayden Ahn
Original Source: Raul Valente, Raquel Ruivo, and others. Science Journal for Kids and Teens, April 2025
https://www.sciencejournalforkids.org/articles/how-did-mammals-evolve-to-live-in-the sea/; https://link.springer.com/article/10.1186/s12915-024-01984-0
Cover created by Jayden Ahn
Abstract
Background: Cetaceans (whales, dolphins, and porpoises) are marine mammals, but about 50 million years ago their ancestors roamed on land instead of cruising through the seas. Later these cetaceans evolved to live in the water, but this took a lot of adaptation. They had special traits like being half-awake when sleeping, controlling blood pressure, conserving heat in cold water, etc. According to scientists, neuropeptides (chemical messengers) may have helped this happen.
Objective: Luckily, neuropeptides are found in every single mammal, so scientists wanted to know how these "chemical messengers" helped with the evolution of marine mammals.
Method: Researchers observed 12 neuropeptides related to the special traits of the cetaceans. Due to the microscopic size of these "chemical messengers," they looked at their DNA sequences instead. They got DNA sequences for the neuropeptides using online databases; they did this for 202 mammal species, including 41 species of cetaceans. They had a program that gave each DNA sequence a score of 0 to 5, with 0 being the best. They then compared the scores of cetaceans and land mammals.
Results: The results showed that cetaceans have lost the ability to make as many neuropeptides as land mammals. This means many cetacean neuropeptides had a score of 2 or higher. The missing neuropeptides were for important traits like sleep and feeding.
Conclusion: Cetaceans, whose ancestors used to be land mammals, have evolved to live in the sea. This study found that cetaceans lost the ability to make many working neuropeptides, and that this loss is what helped them adapt to life in the ocean. Understanding how this happened helps scientists investigate how other mammals also adapted to their habitats. This is not the only major habitat change - the ancestors of bats used to climb trees, and now bats fly. Look at how much nature changed in a span of millions of years. Maybe the next thing will be a flying raccoon, but who knows what the future holds for us.
