CLOSE
Original image
Thinkstock

How Long Does DNA Last?

Original image
Thinkstock

Even minimal exposure to forensic science on shows like CSI and NCIS will impress upon a viewer what a whopping big deal DNA analysis is. It’s the opposite of circumstantial evidence: undeniable proof of someone’s identity that is impossible to fake, short of swapping out one sample for another. The technique may be applied to murder victims or long-dead English kings or illegitimate children and their custody-dodging fathers—any subject from which intact genetic information can be extracted—and that's what makes DNA as valuable a tool in anthropological study as it is in police investigations. For a long-dead subject, DNA has an expiration date, but when exactly is it?

The entire formula for human life is encoded in the sub-microscopic molecules of deoxyribonucleic acid, and has been throughout all stages of evolution. Like fingerprints, genetic code is particular to an individual, which makes it a unique identifier in the absence of other information, like modern dental records. DNA, however, is fragile, and breaks down over time. How long the decomposition process takes will vary with the circumstances under which it is found. Take, for example, if DNA is exposed to the elements: Like the human body itself, DNA decays with increasing rapidity in the presence of heat, water, sunlight, and oxygen. Those essential conditions of life also speed the process of death, potentially rendering DNA useless for analysis in a matter of weeks.

Scientists have estimated that under the most ideal conditions, DNA can theoretically survive for a maximum of one million years. Although a team of researchers recently claimed to have discovered 419 million-year-old genetic material belonging to prehistoric bacteria in the Michigan Basin, others in the field have loudly contested the claim, especially in light of an earlier sample thought to be 250 million years old, but later proven contaminated by the presence of modern DNA. The oldest actual DNA samples hail from Greenland (the icy one, as opposed to Iceland, the green one), extracted from beneath a mile of ice, a “perfect, natural freezer” for DNA preservation. The 450,000 to 800,000-year-old samples provide evidence of green life on the now largely barren landmass.

As far as human genetic material goes, the record for oldest Neanderthal DNA is held by a 100,000-year-old sample found in a Belgian cave. The longest-lasting sample of human DNA was discovered in northeastern Spain, and boasts a survival age of 7000 years. In both cases, techniques pioneered by Dr. Rhonda Roby allowed researchers to use mitochondrial DNA rather than the type found in the cell nucleus; although mitochondrial DNA only contains only partial genetic information, it provides sufficient evidence for identification and is present in greater abundance than nuclear DNA, increasing its odds of surviving.

How long does DNA last? The short answer is that it’s complicated, and determined by a number of unpredictable factors such as weather and the organism’s final resting place. Your DNA may be the molecular legacy you leave behind, but once you’re dead, there’s not really much you can do about it.

Original image
iStock
arrow
Big Questions
Why Do Cats Freak Out After Pooping?
Original image
iStock

Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

Original image
Jonathan Daniel/Getty Images
arrow
Big Questions
Why Do Baseball Managers Wear Uniforms?
Original image
Jonathan Daniel/Getty Images

Basketball and hockey coaches wear business suits on the sidelines. Football coaches wear team-branded shirts and jackets and often ill-fitting pleated khakis. Why are baseball managers the only guys who wear the same outfit as their players?

According to John Thorn, the official historian of Major League Baseball since 2011, it goes back to the earliest days of the game. Back then, the person known as the manager was the business manager: the guy who kept the books in order and the road trips on schedule. Meanwhile, the guy we call the manager today, the one who arranges the roster and decides when to pull a pitcher, was known as the captain. In addition to managing the team on the field, he was usually also on the team as a player. For many years, the “manager” wore a player’s uniform simply because he was a player. There were also a few captains who didn’t play for the team and stuck to making decisions in the dugout, and they usually wore suits.

With the passing of time, it became less common for the captain to play, and on most teams they took on strictly managerial roles. Instead of suits proliferating throughout America’s dugouts, though, non-playing captains largely hung on to the tradition of wearing a player's uniform. By the early to mid 20th century, wearing the uniform was the norm for managers, with a few notable exceptions. The Philadelphia Athletics’s Connie Mack and the Brooklyn Dodgers’s Burt Shotton continued to wear suits and ties to games long after it fell out of favor (though Shotton sometimes liked to layer a team jacket on top of his street clothes). Once those two retired, it’s been uniforms as far as the eye can see.

The adherence to the uniform among managers in the second half of the 20th century leads some people to think that MLB mandates it, but a look through the official major league rules [PDF] doesn’t turn up much on a manager’s dress. Rule 1.11(a) (1) says that “All players on a team shall wear uniforms identical in color, trim and style, and all players’ uniforms shall include minimal six-inch numbers on their backs" and rule 2.00 states that a coach is a "team member in uniform appointed by the manager to perform such duties as the manager may designate, such as but not limited to acting as base coach."

While Rule 2.00 gives a rundown of the manager’s role and some rules that apply to them, it doesn’t specify that they’re uniformed. Further down, Rule 3.15 says that "No person shall be allowed on the playing field during a game except players and coaches in uniform, managers, news photographers authorized by the home team, umpires, officers of the law in uniform and watchmen or other employees of the home club." Again, nothing about the managers being uniformed.

All that said, Rule 2.00 defines the bench or dugout as “the seating facilities reserved for players, substitutes and other team members in uniform when they are not actively engaged on the playing field," and makes no exceptions for managers or anyone else. While the managers’ duds are never addressed anywhere else, this definition does seem to necessitate, in a roundabout way, that managers wear a uniform—at least if they want to have access to the dugout. And, really, where else would they sit?

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios