Good News And Bad News About Humans VS Chimps
There is great genetic similarity in humans and chimpanzees, but there are notable differences between them that are observable; particularly increased brain size and cognitive abilities in humans. Could these factors possibly have anything to do with an increased incidence of cancer in humans? Far-fetched, perhaps, but the researchers at the Georgia Institute of Technology wanted to find out.
John McDonald, chair of Georgia Tech's School of Biology and chief research scientist at the Ovarian Cancer Institute, led a study comparing human and chimp gene expression patterns in five kinds of tissues: brain, testes, liver, kidneys and heart. What they found was a difference in the way that chimps and humans processed the cell death (apoptosis) of neurons in the brain, leading to a reduced incidence of cell death in the human brain. Apoptosis is one of the primary ways our bodies destroy disease.
McDonald led a second study of the data, his report published in the online edition of Medical Hypothesis, in which his group found that the programmed rate of cell apoptosis in humans was consistent among all major tissue groups, confirming his suspicion that the slower rate of cell death was responsible for the higher rates of cancer and other serious disease among humans.
A further analysis of the data showed evidence that the same slower apoptosis rate was also responsible for the larger brain and enhanced intelligence in humans.
"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," said McDonald.