How Long Does Something Have to Be In the Ground Before It's Considered a Fossil?

iStock
iStock

Jelle Zijlstra:

The other answers here say that to be a fossil, something has to be mineralized in some way. The other answers are wrong.

At least, they don’t agree with common definitions in dictionaries and in paleontology. Usually, any remains or traces of an organism preserved in the ground are counted as fossils. People are less likely to use the term fossil for remains from the last 10,000 years (the Holocene, our geological period), but that is obviously arbitrary.

Here is the Oxford English Dictionary’s definition of fossil:

Something preserved in the ground, especially in petrified form in rock, and recognizable as the remains of a living organism of a former geological period, or as preserving an impression or trace of such an organism.

Especially in petrified form, not always in petrified form. They also say that “the term fossil is usually reserved for remains older than 10,000 years."

My textbook on paleobotany (Taylor et al., 2009, Paleobotany, Academic Press) doesn’t give a definition of the word fossil, but it does provide a nice catalog of the various kinds of plant fossils. Those include petrified wood, but they also include compression fossils, which are the result of the original plant material being compressed. No mineralization necessary. Pollen grains are a very common kind of plant fossil, and they are usually preserved unmineralized. Amber can isolate organic material sufficiently that it is preserved virtually unchanged.

Most paleontologists don’t discuss the definition of fossil, because it’s not terribly controversial. In one of my own papers I used the word for remains of the fossil rodent Cordimus hooijeri that are only a few hundred years old and not noticeably mineralized. Nobody called me out on it.

I did find one paper that explicitly discusses definitions: "A New Species of Fossil Ptinus from Fossil Wood Rat Nests in California and Arizona" (Coleoptera, Ptinidae), with a postscript on the definition of a fossil. This was in the context of beetles from woodrat middens, which were preserved as mostly unchanged exoskeletons. The author settled on “A specimen, a replacement of a specimen, or the work or evidence of a specimen that lived in the past and was naturally preserved rather than buried by man.” Again, no reference to mineralization. He discussed using the term fossil only for remains that are more than 10,000 years old; subfossil for remains before recorded history; and nonfossil for remains from recorded history. But that seemed arbitrary and unworkable; recorded history started at different times in different places.

Fossils are the remains of organisms of the past, regardless of their mode of preservation. Where exactly you draw the line between “organisms of the past” and “organisms of the present that just happen to be dead” is arbitrary and it usually doesn’t matter. If you need a definition (for example, if you’re making a list of fossil and nonfossil species), you come up with a reasonable if arbitrary definition. If you don’t need a precise definition, you don’t.

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Why Does Turkey Make You Tired?

iStock/TommL
iStock/TommL

Why do people have such a hard time staying awake after Thanksgiving dinner? Most people blame tryptophan, but that's not really the main culprit. And what is tryptophan, anyway?

Tryptophan is an amino acid that the body uses in the processes of making vitamin B3 and serotonin, a neurotransmitter that helps regulate sleep. It can't be produced by our bodies, so we need to get it through our diet. From which foods, exactly? Turkey, of course, but also other meats, chocolate, bananas, mangoes, dairy products, eggs, chickpeas, peanuts, and a slew of other foods. Some of these foods, like cheddar cheese, have more tryptophan per gram than turkey. Tryptophan doesn't have much of an impact unless it's taken on an empty stomach and in an amount larger than what we're getting from our drumstick. So why does turkey get the rap as a one-way ticket to a nap?

The urge to snooze is more the fault of the average Thanksgiving meal and all the food and booze that go with it. Here are a few things that play into the nap factor:

Fats: That turkey skin is delicious, but fats take a lot of energy to digest, so the body redirects blood to the digestive system. Reduced blood flow in the rest of the body means reduced energy.

Alcohol: What Homer Simpson called the cause of—and solution to—all of life's problems is also a central nervous system depressant.

Overeating: Same deal as fats. It takes a lot of energy to digest a big feast (the average Thanksgiving meal contains 3000 calories and 229 grams of fat), so blood is sent to the digestive process system, leaving the brain a little tired.

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Why Do Dogs Lick?

iStock/MichaelSvoboda
iStock/MichaelSvoboda

​One of the more slightly annoying things our dogs do (or most adorable, depending on who you ask) involves their tongue obsessively licking every crevice of every spot possible in pretty much the whole world. From our faces to our furniture to themselves, some dogs are absolutely in love with licking anything and everything. Although it can be cute at first, it quickly gets pretty gross. So why do they do it?

According to ​Vetstreet, your pup's incessant licking is mostly their way of trying to show affection. When we pick up our dogs or give them attention, chances are we kiss or pat their heads, along with petting their fur. Their way to show love back to us is by licking.

However, there are other reasons your dog might be obsessively licking—including as a way to get attention. Licking can be a learned behavior for dogs, as they see that when they lick their owner, they get more attention. The behavior can seem like something humans want which, to an extent, it is.

Licking is also a sensory tool, so if your dog is licking random objects or areas of your home, they're probably just exploring. It's easier to get a feel for their surroundings if they can taste everything. But licking objects like your rug or furniture can also be indicative of anxiety or boredom (which can often lead to destructive behavior), and a recent study linked excessive licking of surfaces to certain gastrointestinal disorders.

Another reason for licking is your dog wanting to clean themselves and/or spots around them. They've seen it since they were born; animals lick things ritualistically for cleaning and care. If your dog seems to be obsessed with licking themselves or one particular thing, they probably are. (Yes, dogs can have OCD, too.)

As Vetstreet points out, "excessive" dog licking often only seems excessive to the dog's owner, not the pooch itself. But if it's bothersome enough to you, a trainer can often help curb your dog's enthusiasm for giving wet, sloppy kisses. And while strange behavior is not rare for pets, if your dog's licking seems odd or in any way concerning, there's no harm in taking your pet to the vet to check it out—even if it's just for peace of mind.

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