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.
Cu toate că existau foarte puține dovezi, mulți cercetători credeau că toate creierele mamiferelor, inclusiv creierul uman, erau la fel, cu un număr de neuroni care era mereu proporțional cu mărimea creierului.