CANCER may be the price humans have had to pay for being blessed with big brains, according to a new theory.
Scientists have found that our closest relatives, chimpanzees, have distinctly different genes controlling the self-destruction of cells.
Tests on gene activity in brain, testes, liver, kidneys and heart tissue showed that human cells do not "comm
it suicide" as effectively as those of chimps.
Programmed cell death, or apoptosis, is one of the key ways in which the body combats cancer.
Cells with altered DNA that could turn cancerous are often singled out for destruction. However, sometimes this process goes wrong, leading to cancer.
The researchers from the Georgia Institute of Technology in the US believe a weakening of apoptosis may have evolved to allow brains to grow unhindered.
Dr John McDonald, from the institute's school of biology, said: "The results from our analysis suggest that humans aren't as efficient as chimpanzees in carrying out programmed cell death.
"We believe this difference may have evolved as a way to increase brain size and associated cognitive ability in humans, but the cost could be an increased propensity for cancer."
The research was published yesterday in the journal Medical Hypothesis.
