Read the text below.
Scientists have discovered that blue whales evolved into giants only recently.
According to researchers, blue whales can grow over 100 feet, making it the largest species on earth. However, a recent study shows that the creatures only began to grow into giants approximately 4.5 million years ago, during the shift from the warm global climate to the ice age.
The research team used data from both extinct and modern whales to trace their growth history. With the record of their sizes, they found out that the bigger whales evolved while the smaller whales died out. This suggests that a larger size became an advantage for whales during the ice age.
The scientists explained that the whale’s size was key to obtaining food in the midst of extreme conditions. The change in temperature caused a disproportionate distribution of nutrients in the ocean. As a result, the patches of nutrients attracted tiny creatures like krill, which whales feed on. Because krill would cluster in some areas, one big whale could eat a mass of krill in just one swoop. They did this through filter-feeding, a system in which food is strained from the water using the whale’s teeth-like bones.
Changes in the environment have also affected other animals in the past. Around 55 million years ago, an ancestor of the horse was only as big as a modern dog. However, climate change created more grasslands, so the horses needed to run faster to escape predators and find fresh grass to feed on. These resulted into a new horse species that was taller and had hooves instead of toes.