Celestials and Galactus (Marvel Comics)

Leon Genetic Sequence – aging in the Marvel Universe

Game system: DC Heroes Role-Playing Game


The León Genetic Sequence (LGS) is a No-Prize Hypothesis  to explain how time passes in the Marvel Universe. First, let’s quickly review what the problem is, right ?

Why ?

The issue is that the chronicled adventures in the Marvel Universe have been running for decades (since 1962, if you want to zero-in on the “modern age”). This makes the longevity of most of the recurring characters wildly improbable.


There exists an official 10-year timeline solution, but it creates a host of major continuity issues. The official approach is that the history of the Marvel Universe since the Fantastic Four’s fateful flight is always, retroactively, 10 or 13 years ago (depending on versions). Thus, that flight would now have occurred in 2002 or 2005, not 1962.


Of course, issues abound for characters with clear ties with historical events. For instance :


It is, of course, possible to constantly mentally rewrite everything. But this is an endless and rather confusing endeavour. Some Marvel examples :

  • Retconning  Tony Stark as having built his suit in Afghanistan, not Việt Nam (as in the Iron Man movie).
  • Retconning the Punisher as having served in Desert Storm, not Việt Nam. Which arguably doesn’t carry the same historical charge.
  • Retconning the Black Widow as an high-tech industrial espionage expert rather than as a Cold War KGB legend.

But we can’t do that on writeups.org, where we’re sticking as close to primary sources as possible. Occasionally, we can study the chronology of a character and how it can conceivably be adjusted, but it’s a huge amount of work that doesn’t reflect the comics. Our series of profiles for Ms. Marvel (Carol Danvers) include such extra sections.

What ?

The León Genetic Sequence explanation takes another approach to the problem. It allows the events to unfold much like in the comics as published — the protagonists do not age.

This approach has been occasionally used in the comics. For instance Nick Fury’s continuous career from the late 1930s until today was made possible by the mysterious Infinity Formula he was injected with in the 1940s, considerably slowing down his ageing.

Various age suppression factors have been seen beyond the Infinity Formula — such as the Kudrin treatment for the Black Widow (Natalia Romanova), the genetic treatment used for the mutants in the Weapon X project, and so forth. Likewise, many characters have had their aging rebooted, such as when Magneto was reverted to being a child by Mutant Alpha.

The postulate behind the León Genetic Sequence is that age suppression factors are actually carried by many humans and mutants. The explanation for this lies in the distant past of humanity.

Enter the Celestials

The “space gods”, the Celestials, are known to have deliberately engineered the human race along at least two lines:

  • The creation of an Eternal and of a Deviant subrace, like they did with many other races (including the Kree, the Skrulls and others). Eternals have special genetics allowing them to tap cosmic energy itself, while the Deviant have an incredible rate of mutation, making each child completely different from its parents.
  • The activation of an extraordinary potential for paranormal powers, sometimes called the X-Factor Genetic Sequence, in humans. Those abilities can emerge spontaneously, generally during puberty, making the individual a mutant – the so-called homo sapiens superior. They may also be coaxed, often accidentally, through exposure to various radiations, chemicals, etc. making the individual a mutate.
    This potential does not seem to be shared by most of the races engineered by the Celestials, making humanity remarkable in its potential.

The León Genetic Sequence is a part of the second manipulation. Just like humans have a distinct potential for developing mutations and paranormal abilities, they carry the potential for an extended lifespan (about 120 years) and greatly slowed aging once they reach full adulthood. Just like the X-Factor, this sequence remains unexpressed in the vast majority of the population.

How ?

The León Genetic Sequence (“LGS”), when expressed, has several effects:

  • The natural life expectancy of the person becomes normally distributed around a mean of 121 years, with a standard deviation of 10 years.
  • The aging of the person drastically slows down somewhere during their 20s. Some, like Peter Parker, have encountered the phenomenon even earlier – around 17. How slow the ageing becomes varies from individual to individual, but a factor of 3 or even 4 compared to another person is not unusual for bearers of the LGS.
  • The LGS seems to have a genetic affinity for superhumanly powerful, active mutants and mutates. While its chances of spontaneously expressing are at best one in 200,000 (i.e., one in 200,000 person in most populations benefits from the LGS), it seems to be present in more than 80% of superhuman or borderline superhuman mutants and mutates.
    Since this part of the human genome actually has an intelligent designer, it is thought that the X-Factor and the LGS sequences are intended to work together.
  • 34% of the bearers of the LGS will have blue eyes or eyes with a noticeable tinge of blue, even if their ethnicity should make this much rarer (e.g., most African and Asian ethnicities).

More effects

  • LGS bearers tend to frequent each other more often than normal demographics would indicate. It has been theorized that LGS bearers emit subtle cues, perhaps pheromonal, which can be subconsciously picked up by other LGS bearers. While those hypothetical signals remain to be discovered, their existence has not been disproved so far.
    Such a mechanism might be an evolutionary adjustment to enhance some aspect of reproduction — but this seems unlikely since there is no apparent gender differentiation. A LGS-bearer is likely to count a statistically abnormal number of LGS bearers among his friends and acquaintances, but within those the opposite sex is not over-represented.
  • Two LGS bearers will not necessarily produce a LGS-active child, though the chances seem greatly increased. The fertility of both LGS-bearing males and females seem significantly decreased compared to the baseline population, however. This is likely an evolutionary adjustment.
    More generally it has been observed that this low fertility was about right to keep the proportion of LGS-active persons in the population constant. Given the fine balance involved, this is very likely to be a feature in the design of the sequence by the Celestials.
  • Many, but not all, persons with an expressed LGS sequence will have remarkable abilities to withstand many diseases and recover from physical trauma. This is not a genuinely superhuman feature, though — doctors examining those patients just consider them to be very resilient and fast healers.
  • The large majority of LGS bearers will naturally develop a sexually attractive physique. See our height and weight of super-heroes for more about this.
    It has been theorised that LGS-active subjects subconsciously manage their store of body fat to meet their unusual energy requirements and general desire for sexual attractiveness. This theory is based on the hypothesis that mutants and mutates manage the energies and other abnormal physical characteristics within their body though a diluted form of psionic  control over their molecules, based on the same designs as used by Eternals.
    This theory is not well-supported, but attractively satisfies Occam’s Razor . It also has the advantage of explaining the lack of gross physical adaptation of the bodies of high-intensity energy manipulators such as the Human Torch, Havok, Magneto, etc. to accommodate their enormous power.

Even more effects

  • Persons with an expressed LGS sequence retain their youthful ability to absorb vast amount of new information for a longer time than most. This is believed to be related to their excellent healing abilities. In practice, it has been observed that LGS bearers tended to explore more areas outside of their academic specialties (making scientists, in particular, very multi-talented), to be more curious and inclined toward exploration of the unknown, and in some cases to remain in a college environment for much longer than the average.
    Some observers have noted that this youthfulness in knowledge acquisition also seemed to impact behaviour, and made many subjects with an expressed LGS behave in immature ways. There is no study on the matter, though, due to the methodological difficulties it would imply. But this hypothesis is often seen as likely by people who have multiple LGS-active acquaintances.
  • Some psychologists have theorized that this “eternal youth” and health encouraged a behaviour of spectacular risk-taking, by giving some the impression, often subconscious, that they were “chosen” or “immortals” and must have some sort of greater destiny. This line of research is quite interesting, as it helps explain the modest impact of LGS bearers on society throughout History (they tend to get killed due to misconceptions about their relationship with the higher powers in their cultural mythologies). It also helps explainthe drive of some LGS bearers to become costumed adventurers, even when they have no clearly superhuman abilities.

When ?

The León Genetic Sequence has been around since the First Host of the Celestials, roughly one million years ago. While the mutants and mutates seem to have had their frequency among the population dramatically increase for the last few decades, the level of expression of the LGS seems to have remained fairly stable when corrected for the higher number of superhumans since the late 1930s and especially the mid-1960s.

The observation that some people remain young for a very long time is thus a familiar one throughout Earth-616’s various cultures. Marvel Universe humans have long known that it happens to some lucky few, and always has. It thus does not cause surprise — though it does certainly cause jealousy.

It has had little impact on most sociological dynamics. The LGS bearers are usually simply considered to be very lucky people. Compared to the real Earth, this has led to many cultures developing a certain cult of youth and hard bodies, but there’s nothing here that would amaze a XXIst century denizen from North America or Western Europe.

Some backlashes, such as witch hunts or strong respect for the elderly, have likewise been somewhat more common and severe than in the history of the real Earth.

Generally, though, this ’long youth‘ phenomenon is not considered more unusual than other inborn characteristics, such as having a great singing voice or, say, David Bowie’s or Dick Clark’s seemingly supernatural lack of aging. There are simply more cases of this on Earth-616  than in the real world.

By the time concrete research became possible, and answers to the old question of why some people would be lucky to remain young and beautiful for decades became possible, the X-Factor became known to science and overshadowed the question. Still, the discovery of the LGS was one of the reason for the historic push behind the Human Genome Project on Earth-616.

So far, no reliable way (and certainly no public, non-monstrously-expensive way) has been discovered to synthesize or express the León Genetic Sequence. Furthermore, there is no strong scientific consensus around it. Many researchers, in fact, consider the notion to be overly simplistic.

Whither DC ?

The DCU doesn’t have convenient genetic engineers space gods. And it generally puts less of an emphasis on genetics as the go-to explanation, with the exception of the metagene.

Still, some GMs might wish to use the LGS in their DC campaign. Once this decision has been taken, there are numerous possible source for an LGS-like phenomenon. Random ideas include:

  • The first pass of the Godwave is the simplest approach, with “long youth” humans appearing as the gods do.
  • The Ian Karkull incident, which altered the aging of many JSA members, might have echoed up and down the timeline. If so it changed reality to add people with LGS-like characteristics in the entire past, present and future.
  • It might have occured during the Crisis, and then have become part of the New Earth’s history. A possible approach would be that the death of the Immortal Man occurred differently. Perhaps he deliberately sacrificed himself so that many people on the soon-to-be New Earth would be blessed with LGS-like characteristics.
  • One may want to keep the Kirby connection by invoking the Third World. Perhaps an Old God of youth was killed as the Third World gave way to the Fourth had his essence scattered on Earth. Perhaps the LGS is actually a sort of anti-Anti-Life Equation, granting superior free spirit, non-conformity, youth and vitality to those happy subjects who host it in their subconscious.

By Sébastien Andrivet.

Helper(s): Roy Cowan, Frank Murdock, Adam Fuqua.