In humans, brain mass relative to body mass is the largest among all members of the animal world. The nearest competitors are the chimpanzees and dolphins, the dolphins are ahead for this indicator chimpanzees. Up to now, been a mystery to scientists, from where the dolphins are large brains?
The ancestors of cetaceans are herbivores such as cows today with a little brain. When whales and dolphins "moved" to live in the water and changed the "land" on the fins of the limb, the weight of their brain has tripled. To understand how this happened, researchers at Wayne State University compared the genomes of dogs, horses and cows with the genome of the bottlenose dolphin (view dolphins).
All of bottlenose dolphins for 10 thousand DNA sequences coding for proteins, the researchers found 228 mutations. Since these mutations were "approval" of natural selection, it means they have to give the Dolphins an advantage. 27 of mutations found are associated with the nervous system. Mutations of, for example, were found in transthyretin gene regulating the transfer of glucose through the blood-brain barrier and microcephalin gene which determines the size of the head and brain. Other mutations in the genome facilitated the formation and destruction of synapses, which were essential to cognitive performance. A number of mutations was associated with metabolism and cardiovascular system, some changes in the genome of the bottlenose concerned mitochondria and oxygen delivery to the tissues. Improving the performance of mitochondria due not only to the relocation of dolphins in the water, but also the need to ensure energy greatly increased the brain.
The study authors noted that the dolphins have adapted to aquatic life extremely quickly - in 5-10 million years. Based on this, one would assume that for cetaceans in general characterized by a high level of gene mutations, but scientifically proven that it is not: in modern cetaceans mutations in the genome are less frequent than in other species. According to researchers, this slowing of mutational processes may be a side effect of intensification of metabolism and tripling of the brain.
In general, the results of research for scientists were not very surprising. However, they hope that the findings and the study of the brain of other animals will learn more about the evolution of the human brain. In distant from each other primates and dolphins in the evolution of the nervous system has developed to a similar level, in addition, many mutations in humans and dolphins are the same, so it is likely that the mysteries of the human brain will help reveal not monkeys, and dolphins.
According to the materials Sciencemagis.ru