blog posts

Why Do We Die? But Do Some Species Live Very Long?

Why Do We Die? But Do Some Species Live Very Long?

Some Mermaids And Their Relatives Offer Exciting Clues About The Possibility Of Immortality; But Why Do Most Species Die So Quickly?

The Heather is a strange and wonderful aquatic creature that may not get much attention. Named after an ancient Greek mythological snake with many heads that could regrow if severed, the animal is a relative of jellyfish, sea anemones, and corals that live in freshwater.

Looking like a dandelion seed, Heather has nothing special to show, with an elongated body and a bunch of tentacles at one end. Still, hyders have a remarkable feature that makes scientists curious about them: they have the power to regenerate. If you split Heather into pieces, each piece will become a new person.

The regenerative properties of the hydra have attracted the attention of biologists looking for evidence of immortality in nature. Why do these species seem not to die of natural causes? Is death inevitable?

In the mid-20th century, aging was described as a trade-off between reproduction and cell maintenance. First, the body of living organisms uses its resources to grow and maintain its health, that is, to keep its cells. During childhood and adolescence, the emphasis is on surviving and becoming as strong and healthy as possible. After sexual maturity, the priority changes to reproduction. Since resources are limited for most organisms, prioritizing copy can come at the expense of maintaining health.

Consider a salmon that swims upstream to spawn and dies soon after.

It’s all about giving the salmon the best chance to reach the spawning grounds; when they do, they make the most of the opportunity.

The chances of a salmon swimming downstream, surviving another year at sea, making the same trip, and spawning again is so small that natural selection never works in their favor. Moreover, they have already passed their genes on to the next generation.

Scientists’ understanding of why living things die is a bit more precise. When organisms reach sexual maturity, the force of natural selection weakens, and the aging process begins, eventually leading to death.

freshwater hydra

Freshwater Heather, named after the ancient Greek mythological snake, has a remarkable ability to regenerate.

Throughout life, our genes accumulate mutations. Most mutations have no effect or are harmful, and very few can be beneficial. Some modifications are random, and others result from diet or external factors such as UV light.

Gabriella Kontorides, an evolutionary biologist at Oxford University’s Department of Anthropology, says that before puberty, any gene mutation that reduces the organism’s chances of reproduction or even kills the organism before it reproduces is strongly selected. However, the force of natural selection weakens after the organism reaches sexual maturity and can pass its genes on to the next generation.

Consider spawning salmon. He is doing well to reach adulthood and reproduce. Her offspring are also likely to have a high chance of spawning. If a post-spawning salmon had a gene mutation that randomly extended its lifespan, meaning it lived an extra year (though this is extremely unlikely), the resulting offspring would have a distinct advantage over their siblings. Salmon without mutations have already reproduced.

From the point of view of natural selection, there is a slight advantage in continuing to stay healthy after reproduction. As a result, any gene that provides this possibility will not be under selective pressure, leading to an increase in the frequency of that gene.

Kontorides says:

One wants to survive; But at that point, natural selection doesn’t do much about this; Because there is nothing else to give to the next generation.

However, not all creatures are as extreme as a salmon that only spawns once. Some live longer to have more children. Most mutations that occur in our DNA have a negative effect or no effect at all. Our body can repair part of this DNA damage, But the ability to repair DNA decreases with aging due to the weak forces of natural selection.

Aging and death occur in two ways: first, the accumulation of harmful mutations due to weak natural selection, and second, the presence of mutations that may be useful for reproduction, But in terms of longevity, they have a negative effect.

One of the examples of the second case is BRCA gene mutations. These mutations significantly increase the risk of ovarian and breast cancer, But they are also associated with more fertility in women carrying them. Therefore, BRCA gene mutations may have a reproductive advantage early in life but be associated with a higher risk of health problems in old age. Still, because natural selection weakens after puberty, the reproductive benefit outweighs the resulting harm.

Kaitlin McHugh, a biologist at Oregon State University, says:

Everything that happens early in life is more critical than after reproductive age; Because fertility is what matters.

Cell senescence, in which cell division ceases, may be another example of an early-life advantage with a late-life disadvantage. Cellular aging protects us against cancer; Because it can prevent the proliferation of cells with DNA damage. However, during aging, senescent cells can accumulate in the tissues and cause damage and inflammation and cause age-related diseases.

Although most species age, there are exceptions. For example, many plants show partial senescence, and some species live for thousands of years. One of the great examples is the Pandu tree in the Fishlake National Forest in Utah. This tree is a colony of male aspen trees that are genetically identical and connected by a root system. This tree covers more than 400,000 square meters and weighs more than 6,613 tons. According to some estimates, this tree is more than ten thousand years old.

A relative of the Heather, the immortal jellyfish, has another ingenious way of ensuring longevity: if injured, diseased, or stressed , the creature can revert from its adult stage to its primary life stage, called a polyp.

Salmon / salmon

The grueling journey of the salmon from the ocean to the upstream takes its toll on the fish, causing them to die shortly after spawning.

There is also the suggestion that some species become more successful as they age, says Alexey Maklakov, a professor of evolutionary biology and biogerontology at the University of East Anglia in the UK. Of course, there is no strong evidence supporting this phenomenon, which is called negative aging. Maklakov says:

If the ecology of the species is such that, for some reason, reproduction is generally low or unable to reproduce early in life, this changes how selection operates.

A single male may control an entire group of females. The size of that group, and therefore the number of offspring it can have, may increase with age. Thus, his reproductive efficiency continues to grow as he ages. Examples of this may be seen in animals that mate with harems, such as porpoises or deer.

While it’s true that some species can maintain reproductive power as they age, they aren’t actual examples of negative aging, and the studies that make that claim are flawed, Malakoff says. Ultimately, the porpoise cannot control the harem indefinitely.

Sex may play a strange role in how we age. According to a study by Megan Arnott and Ruth Mace of University College London, women who have regular sex experience menopause later. The authors suggest that this is an example of a trade-off in that if there is no intercourse and therefore no chance of pregnancy, continued investment in ovulation is not adaptive, and the energy expended on ovulation is better used by the rest of the body.

In the rest of the animal kingdom, greater fertility appears to accelerate aging.

For example, bats with more offspring live shorter lives than bats with fewer offspring. Perhaps, given the opportunity to reproduce, they devote all their resources to reproduction. “Creatures that reproduce very well early in life don’t do well late in life,” says McHugh. (Headers are an exception to this rule. Their fertility rate does not seem to decrease during their lifetime.)

There are also species whose lifespan varies significantly between sexes. Ants, bees, and termites usually have a king or queen that may be fertile and live longer than sterile workers. In the case of these organisms, why doesn’t the cost of reproduction reduce their lifespan? The answer may be that the king or queen is protected against most of the threats that workers face, and their different lifestyles mean that theories of aging do not apply to them in the same way.

Grandmother and granddaughter / grandmother

Having a grandmother in the living environment can have many advantages for the family.

So, if reproduction has such a profound effect on our lifespan, why do humans continue to live long after they stop having children? According to the “grandmother hypothesis,” the survival of elderly relatives is essential; Because reproduction is expensive and risky.

A grandmother can ensure the survival of some of her genes by investing in her grandchildren; thus, longevity can be an advantage from a natural selection point of view.

Kontorides says:

Families with grandmothers around have much higher reproductive fitness, perhaps because the mother can focus on having more children and the grandmother helps raise the previous children.

Since grandchildren share only 25% of their genes with their grandmother, they are as related to her as nieces and nephews. In another theory, Maklakov says:

Perhaps in the past, not enough women survived to reproduce at age 50. So natural selection was very, very weak on what happened to female reproduction at age 50.

Maklakov’s viewpoints are the same central principle of aging: natural selection weakens after reproduction. Most of what happens to us as we age may not be pleasant, But there is no solid evolutionary force to protect us against it.