Biology

Why haven't we evolved immortality? The answer is in our genes

Why haven't we evolved immorta...
To test a theory about why we haven't evolved to be immortal, researchers have identified certain genes that affect lifespan and switched them off, helping worms live longer
To test a theory about why we haven't evolved to be immortal, researchers have identified certain genes that affect lifespan and switched them off, helping worms live longer
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To test a theory about why we haven't evolved to be immortal, researchers have identified certain genes that affect lifespan and switched them off, helping worms live longer
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To test a theory about why we haven't evolved to be immortal, researchers have identified certain genes that affect lifespan and switched them off, helping worms live longer

If evolution works by selecting for the most advantageous genes, it begs the question: why haven't we evolved immortality? According to a decades-old hypothesis, certain genes that promote reproductive success also promote aging later in life, and now a study from Johannes Gutenberg University has identified some of these genes. The team also found that switching off those genes dramatically extended the lifespan of worms.

Getting old and dying is a natural part of life, but that doesn't mean we aren't interested in slowing or stopping it. There's a huge body of science dedicated to fighting aging at the genetic level, to find ways to extend not just our lifespan but our "healthspan" – the percentage of our lives in which we enjoy good health. There's not much point living to 110 if we spend our last 30 years completely bedridden.

But why hasn't evolution already done the heavy lifting for us? Individuals with traits that help them live longer are more likely to pass on their genes, so in theory, aging should have been entirely weeded out by now. To explain this apparent contradiction, in the 1950s biologist George Williams proposed the theory of antagonistic pleiotropy (AP), which operates on the principle of "benefit now, pay later." Essentially, the idea goes that evolution would select for genes that improve an individual's reproductive success in youth, and ignore any negative repercussions later in life because the genes have already been passed onto the next generation.

Williams' theory has since been backed up mathematically, and its effects can be seen in nature, but direct evidence had proven elusive. To test the idea, the Johannes Gutenberg team screened the genes of a worm species called C. elegans, and identified 30 genes that seem to fit the AP bill, helping in youth but turning against the animals in old age.

"The evolutionary theory of aging just explains everything so nicely but it lacked real evidence that it was happening in nature," says Jonathan Byrne, co-lead author of the study. "Evolution becomes blind to the effects of mutations that promote aging as long as those effects only kick in after reproduction has started. Really, aging is an evolutionary oversight.

"From a relatively small screen, we found a surprisingly large number of genes that seem to operate in an antagonistic fashion. Considering we tested only 0.05% of all the genes in a worm this suggests there could be many more of these genes out there to find."

To the team's surprise, many of the identified genes have a particular function in common: they regulate a vital process called autophagy. This is the recycling mechanism of cells, where they degrade to clear out the "cellular garbage" before it piles up and damages the cells. Autophagy works well in young organisms but is known to slow down and cause chaos later in life, so switching it off at a certain age could help improve both healthspan and lifespan.

"This could force us to rethink our ideas about one of the most fundamental processes that exist in a cell," says Holger Richly, principal investigator of the study. "Autophagy is nearly always thought of as beneficial even if it's barely working. We instead show that there are severe negative consequences when it breaks down and then you are better off bypassing it all together. It's classic AP. In young worms, autophagy is working properly and is essential to reach maturity but after reproduction, it starts to malfunction causing the worms to age."

The researchers found that by inactivating autophagy in the C. elegans' neurons, the worms stayed healthier for longer and their lifespan increased by an extra 50 percent. The researchers aren't yet sure of the mechanism behind the healthier neurons, but if the research can be applied to humans, it could not only improve our health- and lifespan, but combat neurodegenerative diseases like Alzheimer's, Parkinson's and Huntington's.

"Imagine reaching the halfway point in your life and getting a drug that leaves you as fit and mobile as someone half your age who you then live longer than, that's what it's like for the worms," says Thomas Wilhelm. "We turn autophagy off only in one tissue and the whole animal gets a boost. The neurons are much healthier in the treated worms and we think this is what keeps the muscles and the rest of the body in good shape."

The research was published in the journal Genes & Development.

Source: Johannes Gutenberg University

11 comments
ErstO
Interesting, but if “evolution works by selecting for the most advantageous genes” evolution more or less stops after the reproductive years..... It works..... Yes there may be a few human females that can still reproduce late in life, but those genes would be drowned out in a few generations because evaluation has already found the optimum age cycle for reproduction.... Thats not to say that gene therapy cant extend our lives, but the only way nature would do that is if we kill off all those that can only reproduce in there younger years.
Augure
The answer is to immortality is not in our genes, but neurological limitations: sure you can extend life artificially up to any point, but there is a threshold beyond which the mind, and I say the mind because even artificially extending brain cells or neurons production wouldn't change anything, cannot continue apprehending the world, experiences or reality when it has live to young. Anyone who can project themselve living 100 years, then 500 years, then 2000 years while understanding the changes in mind in their current age (unless you're very young) can quickly see how this becomes hell.
ZubinB
This is because humanity as a species is already 'immortalized' via the means of reproduction and it isn't as efficient to try and get individual humans to carry on living for multiple decades as it is than to simply start again as a baby, which is overall more beneficial towards the species as a whole which is what matters as it will allow it to continue to grow and evolve and offers better protections against potential extinction events.
EUbrainwashing
To look at the conundrum from the perspective of the individual is to miss how the 'system' works or, more to the point, what the system is actually working for and towards. Evolution is a fine tuned machine but the individual is only a cog in the mechanism. Humans happen to be self-aware cognitive individuals, that want to live, but that is because the DNA that comprises them has found this to be the best way to perpetuate. Not to perpetuate humans, or worms, but to perpetuate itself. If my conciousness is just a vast set of data and algorithms we know it is dependent on starting-off and then residing in a brain as the hardware in which our conciousness must be accommodated to 'run'. As yet at least, we are not able to culture a new body and brain and jump our conciousness into that to motor off in. DNA is able to roughly approximate the trick that the data and algorithms which comprise living conciousness cannot perform. DNA finds as close to a match for itself and splits the difference. If it does not all replicate, in exacting detail, into the future most of it does and what gets left behind is a cost paid for the advantage of gaining incremental evolutionary improvements each time it is incarnated into a new life.
dmitriy
Hm, and for what reason these autophagy’s genes rapidly start to malfunction at some age? Wouldn’t it be wise to foster the efforts to find the deeper issue causing this failure? It should also lie somewhere in worm’s DNA but some other genes should be responsible for that.
piperTom
It will be great if science learns how to switch off aging, but I despair of getting it past the FDA... in my lifetime.
JonathanPDX
Immortality sounds like a cool thing, but given the horrors man manages to enact in the (normally) seven or eight decades of life, it's probably a good thing our species doesn't live longer. At least that gives those who live on some chance to recover from or ameliorate the effects of those "bad apples" who seek to leave their scars upon humanity.
Douglas Bennett Rogers
The twenty somethings that return from successful wars are the ones to reproduce. The cholesterol that stops their bleeding will later clog their arteries.
warren52nz
I wouldn't argue with the experts but it seems simple enough to me. Evolution only occurs when resources are limited because then it becomes a competition for survival and that's how Natural Selection works. If people lived too long, the older non-breeders would use up resources the younger generation could use to breed. And genes degenerate over time so it's better to breed young when the genes are still "fresh". So it's adaptive to the gene pool for the older ones to die off.
JimFox
Immortality- imbecilic concept. Earth is on the brink of the sixth extinction- brought about by humans. If we lived to even 200 yrs, there'd be nothing left to support any living matter by now. We have no idea of how to manage our resources since the dawn of 'civilization'. Nor will we EVER learn.