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The whales have evolved to gigantic dimensions only recently

A team of scientists was able to track the evolution of whale size over the past 30 million years and found that very large whales appeared along several branches of the evolutionary tree only 2-3 million years ago. The increase in ice cover in the Northern Hemisphere during this period likely changed the nature of whale food distribution in the oceans and increased the advantages of large body size. This is according to a study published in the journal "Science

blue whale The increase follows the concentration of prey in the oceans due to the increase in ice cover in the northern continents from PIXABAY.COM

A blue whale, which uses baleen to filter its prey from ocean water and can reach a length of more than 30 meters, is the largest vertebrate that ever lived. In the list of the largest living creatures to date, the blue whale is at the top of the list of largest creatures along with most of the other species of minke whales alive today. This is according to a new study by scientists at the Smithsonian National Museum of History. According to the researchers, only recently in terms of evolution did the whales become huge.

In a study published in the Journal of the Royal Society of Britain on May 24, Nicholas Fainson, curator of the Museum of Fossil Marine Mammals and his collaborators Graham Slater of the University of Chicago and Jeremy Goldbogen of Stanford University, write that they traced the evolution of whale size over more than 30 million years of history and found Because very large whales appeared along several branches in the family tree 2 to 3 million years ago. Increasing ice cover in the Northern Hemisphere during this period likely caused a change in the way whales distributed their food in the oceans and increased the benefits of large body size, the scientists say.

The question of why whales got so big has remained a mystery until now, in part because of the challenges of interpreting an incomplete fossil record. "We don't have the right data," Feinson said. "How do you measure the total length of a whale represented by a collection of fossils?" Pinson recently determined that the width of a whale's skull is a good measure of its overall body size. With this progress, it is time to answer the long-standing question.

The Smithsonian holds the largest and richest skull collections of both living and extinct whales, and the museum was one of the few places that used a collection that could provide the raw data needed to examine the evolutionary relationships between whales of different sizes. Pinson and his colleagues measured a wide variety of fossil skulls from the collections of the National Museum of Natural History and used those measurements, along with published data on other specimens, to estimate the lengths of 63 extinct whale species.

The fossils included in the analysis represent species dating back to the earliest whales that lived more than 30 million years ago. The team used the fossil data, along with data on 13 species of modern whales, to examine the evolutionary relationships between whales of different sizes. Their data clearly showed that whales as large as those that exist today did not exist for most of the history of whaling. "We live in a time of giants," said Goldbogen. "Mining whales have never been this big."

The research team followed the differences in body size that developed about 4.5 million years ago. Not only do cetaceans with bodies longer than 10 meters begin to evolve around this time, but smaller species of cetaceans also begin to disappear. Pinson notes that large whales appeared in several different dynasties at the same time, suggesting that massive size was of some advantage during this time period.

"We might think that the whales got progressively bigger over time by chance, and maybe that could explain how these whales got so big," said Slater, a former postdoctoral fellow at the museum. "But our analyzes show that this hypothesis did not last. The only way to explain why the minke whales became as huge as they are today is if something changed in the recent past and created an incentive to be huge and also caused landings for small ones."

This evolutionary change, which occurred at the beginning of the Ice Age, corresponds to climatic changes that could have reshaped the food supply for whales in the world's oceans. Before ice sheets covered the Northern Hemisphere, food resources were fairly evenly distributed throughout the oceans, Feinson said. But when the ice began to cover the continents, and in certain seasons part of it melted, the nutrients were washed into the coastal waters and caused an increase in the food supply for the marine mammals.

During this transitional period, the whales were equipped to utilize the abundance of small animals and plants such as krill as food. Goldbogen, who studies the feeding behavior of sperm whales, showed that filter feeding is particularly effective when the whales have access to large concentrations of prey. According to him, this eating strategy becomes more effective as the size increases."
Moreover, large whales can migrate thousands of kilometers to enjoy seasonal food supplies. Therefore, say the scientists, the food filtering systems of the sperm whales that developed about thirty million years ago reached a stage where they affected the increase in the size of the whales due to an increase in the concentration of prey in certain places and at certain times of the year."
"The size of an animal affects its ecological role," Feinson said. "Our research sheds light on why today's oceans and climates can support Earth's largest vertebrates, but today's oceans and climates are changing far more rapidly than any changes to date. Will the oceans be able to support both a large number of billions of people and the world's largest whales?"
"The clues to the answer to this question lie in our ability to learn from the deep past of the earth - the melting pot of our contemporary world - embedded in the fossil record."


to the notice of the researchers

for the scientific article

8 תגובות

  1. Why do you insist in your response, Abgad, that the predators are not a factor in evolution? It is clear to me that the size of the sharks is an influencing factor for the size of the whales. Even if we have a debate about the extent of the influence of the predators on the size of the nitropha, I think it is an important factor, which should have been mentioned in the article.

  2. Yehuda
    On what basis do you assume that size is a refuge from predators?
    If so, the antelopes would have grown to larger dimensions. (and having trouble escaping the cheetahs)
    Imagine if the mice were bigger. They would then satiate their predators well. And they would have a hard time finding forgiveness or even escaping to it.
    Regarding the elephants on the islands - there it is better to be small and consume less food.
    When the dinosaurs were wiped out who survived? Mice and the like.
    Evolutionary - a compromise is created between the need to be large (requires a lot of food, a certain immunity, reluctance, good body heat retention, fitness for long journeys) and the need to be small (loses heat quickly but easy to find a den, little food, vulnerable to predators but agile and fast) .
    Another point: evolution does not allow big leaps. Just small, tentative steps. You have 10 children. Not everyone is equal in height. If conditions are created that favor a small population - the largest of them will die with a high probability, and the small ones - with a low probability. After 10 generations you have a small population. This explanation demonstrates what small and hesitant steps are.
    What happened to the leviathans? Probably a huge migration route between seasonal food areas and breeding areas. Evolved from the last ice age. The size advantage is clear, (even if it comes in small steps). No small sardine will make this journey.
    And why do whales have breeding areas that do not overlap the food areas? Interesting question. I have a hypothesis, but the canvas is short.
    And let's not forget that evolution is blind. Sometimes she finds quite ridiculous solutions to simple problems...

  3. for miracles
    Even if it is self-evident, they should have considered the activity of the predators. For example, elephants that find themselves on islands without predators are smaller than usual. Carnivorous inventions increase nitrification for survival. I'm sure the article would have been clearer if the writers had also analyzed the predatory inventions of the time.

  4. In answer to the question at the end of the list:
    If we discard the fate of land animals, then it is known that man has a considerable part in the destruction
    The giant herbivores, rhinoceros, mammoths, bulls, all giants became extinct
    At the end of the last ice age, extinction came because of climate change
    But with the active help of the human population.
    Therefore, the whales' chances of survival are only if there is close guarding,
    It is also appropriate to distinguish between the "Ice Age" in which the world has been for about 35 million years,
    (Since Antarctica "settled" on the South Pole and the continents "closed" on the North Pole)
    and the (last) ice age that ended about 20 thousand years ago.

  5. Yehuda
    It amazes me that you think expert researchers haven't thought of this. Honestly, it's not surprising my friend at all 🙂
    The point is, as I understand it, that your idea was correct, so we would expect whales to have been large in the distant past as well. After all, in the past, there were no shortage of large predators.
    The researchers saw that the whales began to grow 2-3 million years ago, and looked for what changed during this time. In your opinion - is this not what they should do?

  6. It amazes me that the evolutionary factor determined by possible predators of the whales is not considered. It seems to me that even small cetaceans could have evolved under these conditions of cold and food, but if these cetaceans had enemies, then size could have resulted in an evolutionary advantage. Today, for example, the orca dolphin and, apparently, also recommend attacking whale pups. Only size could allow the leviathans to survive against them.
    That's my opinion
    So please respond gently

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