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The human brain contains 86 billion neurons, with 16 billion neurons in the cerebral cortex. [ 2 ] [ 1 ] Neuron counts constitute an important source of insight on the topic of neuroscience and intelligence : the question of how the evolution of a set of components and parameters (~10 11 neurons, ~10 14 synapses) of a complex system leads to ...
Thus, large whales have very small brains compared to their weight, and small rodents like mice have a relatively large brain, giving a brain-to-body mass ratio similar to humans. [4] One explanation could be that as an animal's brain gets larger, the size of the neural cells remains the same, and more nerve cells will cause the brain to ...
An elephant's brain weighs just over 5 kg (11 lb), a bottlenose dolphin's 1.5 to 1.7 kg (3.3 to 3.7 lb), whereas a human brain is around 1.3 to 1.5 kg (2.9 to 3.3 lb). Brain size tends to vary according to body size. The relationship is not proportional, though: the brain-to-body mass ratio varies. The largest ratio found is in the shrew. [57]
Brain of the sperm whale, considered the largest brain in the world. Sperm whales have the largest brain mass of any animal on Earth, averaging 8,000 cm 3 (490 in 3) and 7.8 kg (17 lb) in mature males. [23] The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. [24]
The brain to body mass ratio (not the encephalization quotient) in some members of the odontocete superfamily Delphinoidea (dolphins, porpoises, belugas, and narwhals) is greater than modern humans, and greater than all other mammals (there is debate whether that of the treeshrew might be second in place of humans).
Cephalopods have large, well-developed brains, [8] [9] [10] and their brain-to-body mass ratio is the largest among the invertebrates, falling between that of endothermic and ectothermic vertebrates. [11] The nervous system of cephalopods is the most complex of all invertebrates.
A few lemurs have been noted to have relatively large brains. The extinct Hadropithecus was as large as a large male baboon and had a comparably sized brain, giving it the largest brain size relative to body size among all prosimians. [131] The aye-aye also has a large brain-to-body ratio, which may indicate a higher level of intelligence. [42]
They have one of the highest brain-to-body mass ratios [28] and the largest brain size of all fish. [29] Their brains have retia mirabilia which may serve to keep them warm. [30] M. alfredi has been shown to dive to depths over 400 metres (1,300 ft), [31] while the Chilean devil ray, which has a similar structure, dives to nearly 2,000 metres ...