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Realizing that Fibonacci numbers are predicted for neurons undergoing mitosis during the formation of the Human Brain is implicit in the deduction of Fibonacci. Simply replacing his "rabbit" model by analogy with brain cells us sufficient.
Fibonacci observed that: if a rabbit cell had one baby every month, then as the months passed a series of numbers expressed the rabbit population. Each new rabbit would mature in 30 days, adding offspring of the rabbit population. At the end of any duration, the sum of the previous two durations equals the number of rabbits, or brain cells, produced in the last duration of rabbit births or neuron mitosis.

This is to say, the first rabbit matures in a month, and becomes pregnant for the next month. The population then increases each month according to these numbers: 1, 1, 2, 3, 5, 8...

The next number is always found simply by adding the last two. So, above, 5 + 8, gives the next number of rabbits, which would be 13.