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

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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.

This post originally appeared on Quora. Click here to view.

Is There An International Standard Governing Scientific Naming Conventions?

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iStock/Grafissimo

Jelle Zijlstra:

There are lots of different systems of scientific names with different conventions or rules governing them: chemicals, genes, stars, archeological cultures, and so on. But the one I'm familiar with is the naming system for animals.

The modern naming system for animals derives from the works of the 18th-century Swedish naturalist Carl von Linné (Latinized to Carolus Linnaeus). Linnaeus introduced the system of binominal nomenclature, where animals have names composed of two parts, like Homo sapiens. Linnaeus wrote in Latin and most his names were of Latin origin, although a few were derived from Greek, like Rhinoceros for rhinos, or from other languages, like Sus babyrussa for the babirusa (from Malay).

Other people also started using Linnaeus's system, and a system of rules was developed and eventually codified into what is now called the International Code of Zoological Nomenclature (ICZN). In this case, therefore, there is indeed an international standard governing naming conventions. However, it does not put very strict requirements on the derivation of names: they are merely required to be in the Latin alphabet.

In practice a lot of well-known scientific names are derived from Greek. This is especially true for genus names: Tyrannosaurus, Macropus (kangaroos), Drosophila (fruit flies), Caenorhabditis (nematode worms), Peromyscus (deermice), and so on. Species names are more likely to be derived from Latin (e.g., T. rex, C. elegans, P. maniculatus, but Drosophila melanogaster is Greek again).

One interesting pattern I've noticed in mammals is that even when Linnaeus named the first genus in a group by a Latin name, usually most later names for related genera use Greek roots instead. For example, Linnaeus gave the name Mus to mice, and that is still the genus name for the house mouse, but most related genera use compounds of the Greek-derived root -mys (from μῦς), which also means "mouse." Similarly, bats for Linnaeus were Vespertilio, but there are many more compounds of the Greek root -nycteris (νυκτερίς); pigs are Sus, but compounds usually use Greek -choerus (χοῖρος) or -hys/-hyus (ὗς); weasels are Mustela but compounds usually use -gale or -galea (γαλέη); horses are Equus but compounds use -hippus (ἵππος).

This post originally appeared on Quora. Click here to view.

Can Soap Get Dirty?

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iStock/vintagerobot

When you see lovely little bars of lemon-thyme or lavender hand soaps on the rim of a sink, you know they are there to make you feel as fresh as a gardenia-scented daisy. We all know washing our hands is important, but, like washcloths and towels, can the bars of hand soap we use to clean ourselves become dirty as well?

Soaps are simply mixtures of sodium or potassium salts derived from fatty acids and alkali solutions during a process called saponification. Each soap molecule is made of a long, non-polar, hydrophobic (repelled by water) hydrocarbon chain (the "tail") capped by a polar, hydrophilic (water-soluble) "salt" head. Because soap molecules have both polar and non-polar properties, they're great emulsifiers, which means they can disperse one liquid into another.

When you wash your dirty hands with soap and water, the tails of the soap molecules are repelled by water and attracted to oils, which attract dirt. The tails cluster together and form structures called micelles, trapping the dirt and oils. The micelles are negatively charged and soluble in water, so they repel each other and remain dispersed in water—and can easily be washed away.

So, yes, soap does indeed get dirty. That's sort of how it gets your hands clean: by latching onto grease, dirt and oil more strongly than your skin does. Of course, when you're using soap, you're washing all those loose, dirt-trapping, dirty soap molecules away, but a bar of soap sitting on the bathroom counter or liquid soap in a bottle can also be contaminated with microorganisms.

This doesn't seem to be much of a problem, though. In the few studies that have been done on the matter, test subjects were given bars of soap laden with E. coli and other bacteria and instructed to wash up. None of the studies found any evidence of bacteria transfer from the soap to the subjects' hands. (It should be noted that two of these studies were conducted by Procter & Gamble and the Dial Corp., though no contradictory evidence has been found.)

Dirty soap can't clean itself, though. A contaminated bar of soap gets cleaned via the same mechanical action that helps clean you up when you wash your hands: good ol' fashioned scrubbing. The friction from rubbing your hands against the soap, as well as the flushing action of running water, removes any harmful microorganisms from both your hands and the soap and sends them down the drain.

This story was updated in 2019.

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