Is Cancer The Price For Our Big Brains?

In the last chapter of "Not A Chimp" I suggest that mental illness, in the form of bipolar illness or schizophrenia, may be the price we pay for dramatic brain expansion in human ancestors and ourselves. The idea is that many of the very genes that are thought to predispose us to mental illness have been heavily selected for, uniquely, in the hominid line. Why? Many of them are involved with either building the long-distance circuits that link parts of the brain together, or the energetics of running countless signals across this vast network. The brain may be running at full evolutionary capacity - therefore anything that reduces this flat-out efficiency could result in the symptoms of mental illness.

Now, in this interesting piece in Livescience, comes the suggestion that cancer might be another downside to human brain expansion. It has been noted that many of the genes that have been positively selected for in the human brain are involved in delaying apoptosis - programmed cell death - perhaps to maximize neuron number and density in these enhanced human networks. Since one feature of cancers is cells' invulnerability to switching themselves off, perhaps an evolutionary foundation to greater neuron number has left us open to runaway malignancies?