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Could dinosaurs be the reason humans can't live to be 200 years old?

2023-12-25 21:01:30Lifestyle SHKRUAR NGA REDAKSIA VOX
Could dinosaurs be the reason humans can't live to be 200 years old?
Could dinosaurs be the reason humans can't live to be 200 years old?

All human beings age. This is part of our biology and limits our lifespan to just over 120 years. But not all animals experience aging during their lifetime. The bodies of some animals do not gradually degenerate as they age, as our bodies do.

By Joao Pedro de Magalhaes – The Conversation

When people reach about age 30, their chances of dying double about every 8 years. So even if you are lucky enough to live to be 100, your chances of dying every year will be high. This high mortality reflects many other health problems, such as loss of muscle mass and general weakness, cognitive decline, vision and hearing loss, and many other degenerative changes that characterize the human aging process.

And the reason humans age so visibly may be because our ancestors evolved during the age of the dinosaurs. Compared to other mammals, humans live longer. We have the longest life expectancy of any mammal living on land, and of all mammals in general we are probably second only to whales.

I say "probably" because the animals would need to be kept in confinement somewhere to do a detailed study on lifespan, which for whales is practically impossible due to their size and lifespan. We know that some species of whales and dolphins have menopause, and that with age all mammals show some form of decline in reproductive power.

In fact, all mammals studied show physiological aging, and an increase in mortality with age, although some species – such as rats and voles – age much faster than others – such as humans, whales and elephants. But many species of reptiles, amphibians and fish show no signs of aging.

These include turtles, salamanders and rockfish. A study of 77 species of reptiles and amphibians, published in the journal Science in 2022, showed that the increased risk of mortality with age is not seen in many species of reptiles and amphibians.

It seems like these animals never age. Some of them, such as turtles, may live longer than humans. But if we study these seemingly ageless species for a very long time, they will show some signs of aging.

But it takes a lot of luck to study animals such as the Greenland shark, which is estimated to live up to 400 years. For now, we can say that among reptiles, amphibians and fish, some species not only live longer than even the longest-lived mammals, but they age significantly more slowly.

In addition, some of these non-aging species grow throughout their lives, which means that older females lay more eggs, again in stark contrast to what happens in mammals. These animals disappear mainly from being eaten by predators and from disease. In fact, most animals in the wild don't die of old age, and certainly until the 20th century, most humans did too from infectious diseases. Some reptiles, amphibians and fish are also known for their ability to regenerate tissue.

Amphibians evolved from fish about 370 million years ago, and about 50 million years later reptiles evolved from amphibians. Then mammals evolved from reptiles about 250-300 million years ago. We are all products of evolution, which we see in relics, such as our rudimentary tail (the wasp as it is known today).

Our evolutionary history can have a profound impact on modern times. For example, humans retain evolutionary traits from the time our ancestors roamed the savannah, environments no longer suited to the modern world, from the desire to consume sugary things to behavior that leads to prejudice.

About 200 million years ago, massive volcanic eruptions wiped out 76 percent of marine and terrestrial species. Then, dinosaurs became the dominant predators on Earth. To survive and avoid being hunted to extinction by the dinosaurs, mammals became small, mostly nocturnal, and short-lived.

Our ancestors of this time were nothing like us. They were more like voles and mice, small animals that came out in the dark to catch insects. Under pressure from the dinosaurs, our ancestral mammals had to reproduce rapidly, just like rats do today.

And like rats and voles, our ancestors had a short lifespan. For 100 million years, during the age of the dinosaurs, mammals were at or near the bottom of the food chain. Mammals fell prey more often than predators. During that time there was no reason for mammals to retain processes and genes associated with longevity, such as DNA repair and tissue regeneration systems.

My lifespan lock hypothesis suggests that repair and regeneration systems were lost, altered or disabled during the evolution of early mammals. This imposed biological constraints, which dictate how mammals age to this day.

After the dinosaurs were wiped out when an asteroid hit Earth 66 million years ago, mammals took over the world. An impressive variety of species evolved with a variety of lifespans.

Some species, such as humans, evolved to have longer life spans, but they may have done so under severe constraints left over from the age of the dinosaurs. We can get an idea by looking at species that were not subjected to the same evolutionary pressures as early mammals.

For example, the tuatara, a reptile endemic to New Zealand, can look like a lizard. But it split from snakes and lizards about 250 million years ago. It is sometimes called a "living fossil" because of its slow evolution.

As a 2022 DNA analysis study showed, tuataras are thought to live for more than 100 years, and age much more slowly than human beings. Perhaps they have retained their anti-aging genes, unlike the longest-lived mammals. So the lifespan of humans may be limited due to our evolutionary history.

*Joao Pedro de Magalhaes, head of the department of Molecular Biogerontology, University of Birmingham, England.


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