When observing colonial predators such as hounds, baboons and antelopes, people will be amazed at their intelligence.
In addition, recent studies by evolutionary biologists, John Finarelli, Miichigan University and John Flynn, the American Museum of Natural History, have questioned these hypotheses, or at least is it true for all carnivores? After a large-scale analysis performed on many living and fossil predators about the relative increase in brain size set in the context of evolution, Finarelli and Flynn discovered that The increase in brain size is not always related to herd behavior.
Their research paper is being published in this week's Proceedings of the National Academy of Sciences.
'This herd hypothesis is not always true,' says Finarelli. 'When looking at the relative size of the brain from the point of view of the entire evolutionary history, this hypothesis has lost its persuasion, at least in predators. This study also points out that it is almost certain that increased brain size is due to many different causes in different carnivore groups. '
Flynn also added, 'When analyzing the predators in groups, only the dog-breasted predators are proving to be a recent analysis of the herd brain hypothesis'. Flynn is talking about a 2007 study of evolution that was used to test this hypothesis. This study has suggested that social characteristics have promoted the relative increase in brain size in specific mammals in the following three species: predators, primates and ungulate. Relative development of brain size has sparked interest in many areas of biology and with important impacts on ecology, energy and life history. In addition, previous studies have found a correlation between herd behavior and relative increase in brain and body size for all three groups.
In part of the wider study of Finarelli and Flynn about the evolution of brain size in carnivorous animals, the two re-tested this idea by analyzing 289 terrestrial predators and half of them are fossils. With the analysis of many fossil animals, this is the first study to rebuild brain size throughout the entire life cycle of evolution for this mammalian group. The living predators currently spread on the families including bears, ferrets, cats, dogs and related species. For all terrestrial predators, the authors have compiled a set of data on the number of brain cells (brain size) and body index to estimate the corresponding brain size and formation. into the brain. Then the brain formation data was used to identify the corresponding changes in brain size within specific animal groups (known as reorganizing a growth correlation. fit).
Their specific analysis of the evolutionary history of predators recorded at least six distinct changes in brain size for this group and suggested that the whole cause of the increase in size The brain is much more complex than the original assumptions.Some carnivorous breeds have relatively stable brain sizes (for example, one of the two main predators, cat-like predators, except for small cats), while others like bears Extinct dogs (Amphicyonidae: animals in the form of a half-dog) have a brain that gradually shrinks over time as compared to their ancestors.
However, for dogs, there has been a recent increase in brain size. Finarellli and Flynn have confirmed that the results of a group of animals with this predatory ancestor distorted data on all modern carnivores analyzed in the previous experiment of the Brain Hypothesis. herd. By removing this inaccurate data in the study, we found no relationship between brain size and herd characteristics in other predators. Moreover, even if the animal belongs to the dog family with a large brain, we have not yet shown a clear cause for this association: the larger size of the brain stimulates herd or flock Is herd the cause of increased brain size? The answer may lie in Finarelli's previous research analyzing the evolutionary change in dogs. The 2008 study showed that the increase in brain size began about 10 million years ago with the arrival of the first representatives of modern dogs.
The relationship between brain size and herd size also varies among living predators. If social life is the cause of an increase in brain size for predators or the evolution of large brains that promote colonization, then bears, small cats and ferrets with big brains should be the animals live in the herd. But the reality is not so. Predators still live in the same conditions as their ancestors that do not match the criteria described by the herd Brain Hypothesis, and relatively, hyenas and civets have small brains. can live in groups or live separately.
"This is a big, complex discovery that has helped to generalize the living predators and fossils ' Flynn said. ' If we only analyze live animal forms, it usually won't. This study provides another example and helps to infer that the herd brain hypothesis is not true for all carnivorous species. '
John Finarelli is an assistant professor of geological sciences at the University of Michigan and John Flynn is the curator of the fossil mammal and also Richard Gilder principal, History Museum Of course America. The study was funded by the National Science Foundation, the National Museum of America's Research Foundation, the Graduate Scholarship Fund of the Brown Family and the University of Michigan Fellowship Association.