Just seems really inaccurate. If I find some freak event of nature of a conjoined deer in the woods or a mineral with a different chemical composition that has never been found, is this a rare event? Is it possible that we something like this is more common than we think and our estimations are incorrect?
Specifically is this idea rooted as a scientific conclusion or just “I haven’t really seen anything like it, therefore it’s rare”?
In: Earth Science
You’re asking for a fixed definition of “rare,” like the rare items in a video game, where there is a known amount of items and exactly X percentage of them are classified as uncommon, rare, epic, legendary, etc.
Life doesn’t work that way.
HOWEVER…
There are certain situations where “rare” IS scientifically defined. For example, the classifications of threatened, endangered and extinct species. In this case, the frequency of observation in the wild is determined and a numeric change is calculated between the times of observation (e.g. “last year, we saw X number of animals, and this year, we saw Y number”), and then you can give an animal a classification against a scale that everyone agrees upon. And it’s all very different for different animals, so the classifications have a high margin of error, just naturally.
Science is based on the observable world and the tests and data we gather from that.
If we find *one* pair of albino conjoined twin deer in the woods and it’s the first documented case of an albino conjoined twin deer… then yes, it’s very safe to say it is rare. Is it so rare that it has *never* happened in the history of Earth before? There’s no way of knowing that and it’s probably improbable that in all of history it never happened (although it certainly wouldn’t be impossible if that was the case).
But the point is we only have the evidence we have. If we have evidence of *one* set of conjoined albino bucks from some remote logging camp in Canada… then that’s all the evidence we have. We could sit around all day and say “well maybe there are *twenty* of them out there!” but we have zero evidence of that.
We do, however, have evidence of something like the medical condition situs inversus, the congenital condition where major organs are reversed/mirrored in the torso. And, because we have just not evidence but a *body* of evidence we can say something like “Yes, this is very rare, but based on the data we have… we can estimate that this medical condition is present in roughly 1 out of 10,000 people.” (Which is the real estimated rate, just in case you were curious.)
To return to our earlier example, we can observe enough deer to get a pretty decent estimate on albinism (it’s around 1/20,000) but it would be a lot tougher to get any real data on conjoinment given the extreme rarity. In fact, in poking around out of curiosity… I could only find one example, from a case in 2018, with actual evidence of conjoined fawn twins making it to birth (albeit a stillbirth). So if we consider the probability of ever coming across a pair of conjoined adult deer at all, let alone albino deer… the chances are approaching zero given all the factors at play. If anyone were to discover two adult conjoined deer of any kind, it would be absolutely exceptional in every way. Throw in the albino part (given how hard it is for albino animals to survive in the wild) and it would be jaw-droppingly improbable. You wouldn’t need to conduct a survey of life on earth to say, with great confidence, that you were looking at something rare.
We almost never know the full set of possible outcomes of any process, and therefore can’t know a precise probability for a given outcome. We have to judge against our prior beliefs and understanding of the nature of the phenomenon we observe. If we believe we understand, say, the rate of birth defects in deer populations because they’re well studied and easily observed, then we can be fairly confident an event is rare. If we’ve spent very little time studying and observing a different phenomenon it is much harder to be certain about the rarity of a witnessed event. Not really much more to say.
It’s a statistical thing, and for something to be rare you’d have to define it against something.
The conjoined deer would be compared to other deer. If in the history we’ve got 5,000,000 observations of deer, and only one was conjoined, then that’s fairly obviously rare.
We can also say Gold is rare, compared to other elements found. in terms of the crust area of Earth, Gold makes up about 1 to 5 parts per billion. if you mined totally at random, you’d mine about 150,000 tonnes of material to get 1 ounce of gold.
In some cases were know it by definition, A Royal Flush is rare…there’s no unknowns, we know the exact math of it.
In other cases though you’re right that its possible we didn’t discover something yet, we only know of one planet with life on it. But we don’t actually know enough yet. It may turn out this is a 1 in a trillion occurrence, it might turn out its like 1 in 10.
We used to think Diamonds were more rare than they actually are, they’re still pretty rare but not as much as we thought, and we also now know there are comets or even entire planets that may be almost totally diamond.
There’s statistics for determining the rate of something too. As a guideline there’s something called the rule of 3.
If we’re a company inspecting our own product for defects, if we look at 3,000 products and find no defects, we can say statistically that there’s a 95% chance the rate of defects is less than 1 per 1,000.
The more we look at and find nothing, the more certain we can be that the rarity exceeds a certain amount.
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