Surprising link between elephant testicle temperature and cancer resistance

A new study led by the University of Oxford has found a surprising connection between the temperature of elephants’ testicles and the evolution of cancer resistance from potent anti-cancer genes.

The research suggests that the absence of testicular descent in this species may have driven the development of the genes responsible for safeguarding their temperature-sensitive sperm production.

This intriguing hypothesis could open exciting avenues for cancer researchers, potentially providing major insights into understanding the cellular response to DNA damage in humans.

Peto’s Paradox

Regardless of their large size and higher number of somatic cell divisions, which usually increases cancer risks, elephants defy conventional expectations. 

This phenomenon, currently known as Peto’s Paradox, was initially observed by Richard Peto, an epidemiologist at Oxford, who discovered that, despite their enormous size, elephants and whales tend to be surprisingly resistant to cancer.

Focus of the cancer resistance study

In the current study, Fritz Vollrath – a biologist at Oxford and chairman of the organization Save the Elephants – has argued that the reason for this may be a link between a genetic marker, the TP53 gene, and its protein product p53.

This identifies and neutralizes damaged DNA during cell divisions and consequently impedes the spread of mutations. 

While all animal species – including humans – possess only a single copy of the TP53 gene, elephants stand out by hosting no less than 20 copies of this critical gene. But why have they evolved this nearly magical defense mechanisms against cancer when other animals have not?

According to Vollrath, selection on somatic cells – which make up tissues, organs, and bodies – is usually slow and weak due to the complex mix of healthy and potentially harmful cells.

Moreover, when limited to developments occurring in older age, after most offspring have already been produced, evolution tends to proceed at a gradual pace. However, selection on germ cells, such as sperm and eggs, is much faster and stronger, since it directly impacts the survival of each individual cell.

Elephant testicle temperature

In elephants, this phenomenon is closely related to testicle temperature. While in other mammals, healthy sperm production relies on the testes being several degrees cooler than the core body temperature.

Thus the descent of testicles into the scrotum plays a critical role in cooling them as sexual maturity approaches, elephants lack the genes responsible for this descent. 

This results in elephant testicles remaining inside their bodies even during maturity, which subjects them to high temperatures.

Moreover, due to their bulk, thick skin, unfavorable surface ratio, and heat exchange mechanisms centered on blood flow through their ear flaps, elephants’ body temperature can often rise to levels that are detrimental to mammalian metabolism and healthy sperm production.

Thus, the proliferation of TP53 genes has likely evolved to support DNA stabilization in the spermatogonia and ensure the production of robust spermatozoa to safeguard the germ line, rather than for directly combating cancer.

However, as a side effect, the diversification of p53 proteins also provides significant protection against DNA damage and mutations in the somatic cell lines. This offers collateral advantages of cancer resistance and other harmful processes occurring during aging.

“Elephants provide us with a unique system to study the evolution of a robust defense mechanism against DNA damage and explore the intricate details of the p53 complex in our own battle against cancer and ailments like aging. Novel insights in this field are always important, but especially now that overheating is becoming ever more of an issue also for us humans,” Vollrath concluded.

The study is published in the journal Trends in Ecology & Evolution.

More about elephants

Elephants are the largest land animals on Earth, known for their impressive size and distinct features. They belong to the family Elephantidae and are characterized by their long trunks, large ears, and tusks.

Here’s everything we can tell you about elephants:

Elephants possess remarkable physical attributes

They have a thick, gray skin that is wrinkled and can be up to 2.5 centimeters thick. They have a strong skeletal structure, with large leg bones and pillar-like legs that support their massive bodies.

Their trunks are a versatile adaptation, serving as a combination of a nose and an upper lip. Elephants use their trunks to breathe, drink water, grab food, and communicate through various gestures.

The tusks of an elephant are elongated incisor teeth, which can be found in both male and female individuals. They primarily serve for defense, digging, lifting objects, and stripping bark from trees. Unfortunately, ivory tusks have made elephants targets for illegal poaching.

Elephant testicles remain inside their bodies even during maturity, which subjects them to high temperatures. This has been directly linked to cancer resistance.

Diet

Elephants are herbivorous mammals, consuming vast amounts of vegetation. Their diet consists mainly of grasses, leaves, bark, fruits, and roots. Due to their large size, elephants can consume up to 300 pounds (136 kilograms) of food in a single day.

Social structure

These majestic creatures have an intricate social structure. They live in cohesive groups called herds, typically led by a matriarch—a wise and experienced female elephant. The herd also includes female relatives and their offspring, while adult males often live solitary lives or form temporary bachelor groups.

Communication among elephants is multifaceted. They produce a variety of vocalizations, such as trumpet-like calls, rumbles, and roars, which can carry over long distances. In addition, elephants communicate through visual signals, body language, and the use of their trunks.

Intelligence

Elephants are highly intelligent and exhibit advanced cognitive abilities. They possess excellent memory, problem-solving skills, self-awareness, and empathy. Their brain size and structure are comparable to that of humans and other intelligent mammals.

Importance to ecosystems

These animals play a crucial role in their ecosystems. As they move through their habitats, elephants disperse seeds through their feces, promoting the growth of new vegetation. They also create water holes by digging in dry riverbeds, providing drinking sources for other animals during droughts.

African and Asian elephants are the two main species of elephants. African elephants are larger, with both savanna and forest subspecies. Asian elephants are slightly smaller and have distinct features, including smaller ears and two humps on their foreheads.

Elephant conservation and cancer resistance

Conservation efforts are crucial for the survival of elephants. They face numerous threats, such as habitat loss, poaching, and human-elephant conflict. Organizations and governments around the world work to protect elephants and their habitats, raise awareness, and combat illegal wildlife trade.

Overall, elephants are magnificent creatures, possessing unique physical characteristics, complex social structures, and remarkable intelligence. Their conservation is essential to ensure their continued presence on our planet.

—

By Andrei Ionescu, Earth.com Staff Writer

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.