how do we determine a species has gone extinct? You’re telling me you looked EVERYWHERE?
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We don’t know for sure. It’s a judgement call based on the lack of sightings of a usually-already-rare species despite searches. Declarations of extinction are occasionally wrong, but usually not (in part because a very tiny population is usually not viable anyway and dies out even if a few endlings are still around).
It’s possible that there are members of a species that we simply can’t find. In fact, there are multiple instances of previously thought extinct species being rediscovered.
But, when scientists are aware of a specific population and that population dwindles to the point that none of them are seen for decades, we assume them to be extinct.
We’ve looked everywhere that species has been seen before. If it turns out that somehow we missed some, scientists will say so and correct their statements. But in most cases, its pretty easy to check all the places that species has ever been seen before, and confirm there are none left.
Science is about making theories based on all the information you have available, and if new information shows up, adjusting those theories in response.
Most species have a specific geographic range and habitat type in which they are usually found. If repeated surveys of those places find no sightings or other evidence, it’s reasonable to assume that the species may be extinct. There’s no need to search everywhere.
Sometimes absence of evidence really is evidence of absence. Coelacanth were thought to be extinct for the entire history of biological study, but nobody had a problem dealing with it when we find out that was a mistaken determination.
All science is *provisional* truth. That doesn’t mean there’s no way to determine that a species has become extinct.
The rules have changed over the years… today the world conservation union will only label a species extinct if “there’s no reasonable doubt the last animal has died”…
Usually multiple years of surveying the known areas the animals are/were in turning up no sightings/evidence of them around… this Is imperfect like you say, but works well enough for lots of animals (it’s easy to notice if a rhino is not around a few available watering holes, but hard to notice a specific woodpecker isn’t visiting the same jungle trees)
They can also say it if an animals known habitat gets destroyed, but only if they can also prove the animal wouldn’t be able to survive somewhere else
The fish and wildlife service is charged with checking up on animals on the endangered list every so often so there’s tabs being kept
Sometimes animals re-emerge from extinction
By your same logic, every god that has ever been thought of, including the one I just thought of which shits aged medium rare kobe steaks and pisses 22 year old sour mash Kentucky bourbon, must exist, correct? I mean, we haven’t looked everywhere, right?
It’s when there haven’t been any documented (or reasonably probable) sightings in a certain amount of time. At that point we reach a consensus conclusion that the species in question has gone extinct.
We can’t realistically “look everywhere” and every once in a while we do find something we *thought* was extinct that isn’t.
[https://www.treehugger.com/lazarus-species-extinct-animals-found-alive-4869279](https://www.treehugger.com/lazarus-species-extinct-animals-found-alive-4869279)
You look where the species lives, which can often be a limited area, and see if there is any evidence of them before declaring a species extinct. It is a careful consideration, but we’ve been wrong before, and probably will be again. Scientists have no problem admitting when they are wrong, especially not on this.
A great example of that is family of fish called a [Coelacanth](https://upload.wikimedia.org/wikipedia/commons/b/b7/Coelacanth_off_Pumula_on_the_KwaZulu-Natal_South_Coast%2C_South_Africa%2C_on_22_November_2019.png). Coelacanth fossils were discovered in 1839, with fossils as old as 410 million years old and as recent as the late Cretaceous period, around 65 million years ago, when we stop finding Coelacanth fossils. Given that there were no Coelacanth fossils younger than 65 million years old everyone figured that they just went extinct like a whole lot of things did at the end of the Cretaceous period. Then in 1938 a museum curator from South Africa named Marjorie Courtenay-Latimer, who had told local fishermen to let her know if they found anything strange, got a phone call from a guy who caught a weird looking fish. It turns out that Coelacanths were not extinct at all, they were just very rare. Since they aren’t good to eat fishermen had just been throwing them back when they caught them.
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