Two types of extinction?

[delboy]

It seems to me there are two types of extinction. One due to the population dying out, and one due to evolution into another species. One involves genetic extinction and the other is just evolution and is genetic success. Is there reason to make a distinction between the two? Maybe it's just an emotional thing, but the word extinction seems to imply failure in some way, but it could equally mean great success.

I assume that with fossil species it can never be known which type of extinction occurred (unless it was clearly on an evolutionary line that is entirely extinct now).

[iNow]

Well, if the dichotomy you posit is truly valid, then one reason to treat them differently is that one implies longer-term survival whereas the other implies the opposite.

 

If something "evolves" into something else, then it's not really extinct IMO. It's just different and the new form will tend to be better adapted to its modern environment... more fit.

 

However, if something dies out or is just killed off (for example, due to an asteroid or massive change in climate or mass slaughter/hunting/fishing campaign) that implies complete termination and carries important connotations of finality.

 

This doesn't involve emotions, just correct understanding of terms. I would not say that an organism that has evolved into another version of itself became "extinct," but perhaps that's just me.

[Ringer]

Anything that has could be considered extinct due to evolving into a new species couldn't truly be verified. That's why there is a tendency to say 'so and so' was more like the common ancestor and not 'so and so' WAS the ancestor. So even if there was that dichotomy of extinction it couldn't be verified, so I doubt it would be systematically useful.

[chadn737]

The problem here is when do you make a distinction between the ancestor and the descendant population? With some exceptions, the evolution from ancestor to descendant population will occur at such a rate that one generation will always be able to interbreed with the succeeding generation. It is only over great lengths of time and the separation of many generations do reproductive barriers evolve. Any barrier drawn will be arbitrary....you can't set a specific line saying "here is species A" and "here is species B".

 

In this sense then, what goes extinct is not a species, but a pool of genetic variants.

Edited February 13, 2014 by chadn737

[delboy]

So even if there was that dichotomy of extinction it couldn't be verified, so I doubt it would be systematically useful.

 

This is what I suspected.

 

This doesn't involve emotions, just correct understanding of terms. I would not say that an organism that has evolved into another version of itself became "extinct," but perhaps that's just me.

 

It doesn't feel like it's extinction, particularly if you just think about the next species in the evolutionary line (plus the gradual and indefinable nature of becoming a new species). But taking as an example the common ancestor of birds - surely we have to consider that to be extinct. But we could also consider that it lives on in all extant birds.

 

It seems to me that not all extinction is extinction, strictly speaking.

In this sense then, what goes extinct is not a species, but a pool of genetic variants.

 

Which is also very gradual and even more indefinable than the change from species to species.

[chadn737]

 

Which is also very gradual and even more indefinable than the change from species to species.

 

I would argue the opposite. The organism is a composite of its genetics. A single allele can be defined very clearly, whereas a species is a very muddled term. We can measure the existence and frequency of an allele in a very straight forward way. This has long been the strength of phylogenetics.