Though it was based on very little evidence, many scientists thought that all mammalian brains, including the human brain, were made in the same way, with a number of neurons that was always proportional to the size of the brain.
Walaupun berdasarkan bukti yang sangat sedikit, banyak ilmuwan berpikir bahwa semua otak binatang menyusui, termasuk otak manusia dibuat dengan cara yang sama, dengan sekumpulan neuron yang selalu berbanding lurus dengan ukuran otak.