Within the Same Species, Larger Body Size Means Higher Cancer Risk

Scientists have found that within the same species, the larger an individual's body, the higher its risk of developing cancer. Therefore, for us humans, being tall is not necessarily better; tall people face a considerably higher lifetime cancer risk than short, slender people.

Of course, we cannot apply this standard to compare cancer risk across species. An elephant is far larger than a mouse, yet the mouse has a much higher cancer risk than the elephant. Mice develop cancer more easily than elephants, and more easily than we humans. Elephants are among the least cancer-prone creatures on Earth; over the course of evolution they have developed powerful tumor-suppressor genes, carrying more than twenty times as many copies of the p53 tumor-suppressor gene as humans. Nuclear radiation can cause human cells to turn cancerous, but it is largely helpless against elephants.

Nowadays our society generally regards height as beauty, and average human height has been rising in recent years. This is humanity evolving in an unhealthy direction under sexual selection pressure. The pressure of choosing a mate often drives organisms to evolve flashy but impractical traits; the classic example is the peacock's beautiful tail, evolved to attract the opposite sex, which makes it hard for peacocks to escape predators.

Interestingly, the higher an organism's cancer risk, the stronger its reproductive capacity. Mice lack the powerful tumor-suppressor genes of elephants, but they reproduce far more prolifically. The difficulty the elephant population has in expanding is related to its low cancer susceptibility. Women with BRCA gene mutations face a higher cancer risk, yet scientists have found that women with BRCA mutations have more offspring than average women. A survey of women born before 1930 showed that BRCA-mutation carriers had an average of 6.22 children, compared with only 4.19 in the control group. Although BRCA mutations make women prone to gynecological tumors, they confer a reproductive advantage.

Cancer may thus be a natural product of organisms under sexual selection pressure. The antler tumors that grow on male deer are proliferative tissues similar to human malignant tumors, and they shorten the stag's lifespan. Yet stags still evolve antlers that attract females, in order to win the favor of does and gain the chance to reproduce.

In winter, stags shed their antlers; then in spring and summer the antlers grow rapidly, and with them the probability of antler tumors rises sharply. But stags with handsome antlers gain more mating opportunities, so they consider it worth the cost. Interestingly, ancient Chinese physicians discovered that deer antler has an aphrodisiac effect and used it to treat patients with sexual dysfunction.

So if we do not want more offspring and hope to lower our own cancer risk, there is no need to resent our less-than-imposing stature. Among people of the same height, assuming no malnutrition, the heavier the body weight, the higher the cancer risk and the shorter the lifespan.

Since ancient times China has had a saying: no amount of gold can buy leanness in old age. This shows that our ancestors had already observed a relationship between body type and longevity.