Did natural selection for increased cognitive ability in humans lead to an elevated risk of cancer?

Abstract

Despite the overall genetic similarity that exists between humans and chimpanzees, the species are phenotypically distinct. Among the most notable distinctions are differences in brain size and cognitive abilities. Previous studies have shown that significant differences in gene expression exist between the human and chimpanzee brain. Integration of currently available gene expression data with known metabolic and signaling pathways indicates that the expression of genes involved in the programmed cell death of brain neurons is significantly different between humans and chimpanzees and predictive of a reduced level of neuron apoptosis in the human brain. This pattern of expression is generally maintained in other human organs suggesting that apoptosis is reduced in humans relative to chimpanzees. We propose that a decreased rate of programmed neuron death may have been a consequence of selection for increased cognitive ability in humans. Since reduced apoptotic function is associated with an increased risk of cancer and related diseases, we hypothesize that selection for increased cognitive ability in humans coincidently resulted in an increased risk of cancer and other diseases associated with reduced apoptotic function.