What animal is not prone to cancer?

Cancer seriously affects the health of human beings, so we attach great importance to it
.
But cancer is not just a problem for humans.

However, not many people know how high the risk of wild animals dying from cancer is
.
After all, wild animals face many health killers, and any serious disease may cause them to die from starvation or predation, and it is impossible to trace the cause

A few days ago, an international research team published a paper in the top academic journal "Nature", reporting their new findings on the risk of mammalian cancer deaths
.

Some scientists who wanted to clarify this problem thought of an alternative: they turned their attention to the zoo, because the zoo, as a professional place for the protection, breeding and research of wild animals, has traceable records of the animals’ age, sex, and living conditions.
Some animals still have records made by a veterinary pathologist to confirm whether they have cancer
.
In this way, the study covered a total of 191 different mammals and collected relevant information on more than 110,000 adult individuals

In general, this large-scale study shows that deaths caused by cancer are common in mammals and also common in different species.
The risk of cancer death ranges from 0 to 57%
.

▲The risk of cancer death in various mammals (picture source: reference [1])

Carnivores vs.
Herbivores

However, for mammals with different diets, the risk of cancer is different
.
Researchers have found that carnivores are particularly vulnerable to cancer, especially animals that feed on other mammals, such as clouded leopards, red wolves, and South African foxes (bat-eared fox).

In contrast, the "vegetarian" artiodactyls seem to have a strong ability to fight cancer
.
For example, researchers examined nearly 200 Indian antelopes (Antilope cervicapra) and found that all were insulated from cancer

▲The relationship between different dietary composition and cancer mortality.
Gray means little or no eating, and yellow is a staple food or a secondary food (picture source: reference [1])

The researchers' explanation is that mammals that eat meat have a higher risk of cancer, which may be due to the low diversity of their gut microbiome due to a high-fat, low-fiber diet
.
On the other hand, these carnivores living in zoos exercise much less than the amount of exercise required for hunting under natural conditions under human captive conditions, which may also increase the risk of cancer

Big animal vs.
small animal

We know that the occurrence of cancer is often related to mutations that occur when cells divide.
Some mutations make cells grow and proliferate uncontrollably, leading to cancer
.
Therefore, in theory, an individual with more cells has a higher chance of developing cancer

However, this “rule” between body size and cancer risk seems to be true only in the same species, and cannot be compared between different species
.
For example, human cells are about 1,000 times that of mice, but there is not that obvious difference in cancer risk

This study used adequate sampling and data to further support Peto's paradox: the increase in body size and weight between different species did not increase the risk of cancer, and even slightly reduced it
.
For every doubling of body size, the cancer mortality rate drops by approximately 2.
8% to 2.
9%
.

Long life vs.
short life

Cancer is an age-related disease.
Generally speaking, the older the age, the more mutations the cells accumulate, and the risk of cancer also increases
.
However, for different species with different natural life expectancy, the relationship between lifespan and cancer risk also has the same "Peto Paradox" as body type
.

The evidence provided by this study shows that as the life expectancy of animals increases, the risk of cancer death increases only slightly
.
For example, adult life expectancy has doubled from 16 years to 32 years, and cancer mortality has increased from 2.
8% to 3.
7%
.

▲The risk of cancer death in mammals is largely independent of the animal's body size (left) and adult life expectancy (right) (picture source: reference [1])

The researchers concluded that these results indicate that while mammals are evolving toward the two characteristics of increased body size and longer lifespan, more effective tumor suppression mechanisms have also evolved together
.

Note: The original text has been deleted

Reference materials:

[1] Vincze, O.
, Colchero, F.
, Lemaître, JF.
et al.
Cancer risk across mammals.
Nature (2021).
https://doi.
org/10.
1038/s41586-021-04224-5

[2] Cancer risk across mammals.
Retrieved Dec.
23, 2021 from https://