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This is a prime candidate for an MFD on the basis that it's
not an invention but is a naming. It may also be
considered MFDable on the grounds of bleedin'
obviousness,
but time will tell.
On the plus side, it's not a recipe.
In another discussion here, the topic of extinction came
up
in the context of mankind's possible future demise. The
point made was that, of all the species that have ever
lived, the overwhelming majority have become extinct
at
some point.
Well, no they haven't. At least not the overwhelming
majority.
Consider the thylacine (Tasmanian tiger or marsupial
wolf)
and Australopithecus. The thylacine is certainly extinct
(as
far as we know), and there was a precise moment when
the last member of the species died, in a zoo. Game
over.
On the other hand, if our understanding of human
evolution is correct, there was never a last
Australopithecus. The species (actually Australopithecus
is
a genus, but I'm thinking of whichever species is our
distant ancestor) evolved, and eventually became so
different that we recognise it as a different species,
Homo
habilis (there is a lot of argument about the details, but
you get the idea). Homo habilis then evolved into Homo
heidelbergensis, which then evolved into Homo sapiens.
The point is, there is no time in pre-history when an
Australopithecus, Homo habilis or Homo heidelbergensis
could look around and say "I'm the last of my species".
All
of those species are extinct, but none of them went
through a process of extinction.
Similarly, the ten million or so species alive today are
not
the only species that have not yet become extinct. Each
of
those species can trace its ancestry back through a chain
of
previous species. Any species which lies on a path from
the first life to a living species cannot be said to have
undergone extinction in the same sense as the thylacine.
Of course, many species, like the thylacine, failed to
leave any
descendent species; and all of today's species share
common ancestors. But, nevertheless, it is a
misconception to say that today's surviving species are
the
only "non-extinct" ones.
This is particularly true when catastrophists argue that,
since most species have become extinct, humans are
likely
to become extinct too. To say that is to say that
Australopithecus became extinct, which in turn is to say
that our distant ancestors became extinct.
Get to the point [Buchanan].
OK. My point is this. It would be useful, in discussions of
evolution, to distinguish clearly between species which
simply stop, such as the thylacine, without leaving any
descendant species; and those which become 'extinct'
only
in the sense of giving rise to a new species.
If there is any invention in all of this rambling (which I
doubt gravely), it is the proposal of a new term which
distinguishes these two types of 'extinction'.
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// those which become 'extinct' only in the sense of giving
rise to a new species // |
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Such as, say, *homo erectus*. |
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It's a question of speciation. If the original line split, evolved into another species, and then the original went extinct, that's still a true extinction, as there was a speciation event. |
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If instead, the species, in its entirety evolved, then it is questionable whether the two variations can truly be considered separate species, as no speciation event occured (to whit, there was never a point where living memebers of the "different species" couldn't interbreed). |
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//If the original line split, evolved into another
species, and then the original went extinct, that's
still a true extinction, as there was a speciation
event.// |
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Well, I disagree. Take humans and Neanderthals
(ignore any of the speculation about inter-
breeding, let's keep it simple). They could both
trace their ancestry back through Homo habilis
(say). After the split which led to Neanderthals
and Homo sapiens, Neanderthal's went extinct, in
an absolute sense. Clearly Homo sapiens is not
extinct. Is it true to say that their common
ancestor (habilis) went extinct in the same sense
that the Neanderthals went extinct? It's possible
to imagine the last Neanderthal dying with no
children; but it's not possible to imagine the last
Homo habilis dying with no children, or we would
not be here. |
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Technically, if a species "as a whole" evolves, then
technically there wouldn't be an extinction; but
we would look back at the fossil record and call
two or more species, even if we had difficulty
partitioning them; we'd still say the original
species was extinct. (And I am not suggesting
that
evolution is a smooth, continuous process;
therefore we often see distinct species, and only
rarely find the intermediates, even if the species
evolved 'as a whole'). |
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The point I was making is that there are huge
numbers of species which we call 'extinct' but
which, as ancestors of extant species, cannot be
cited as evidence for the idea that all species
(including humans) to have gone through a
process of extinction, even though they become
extinct. |
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To come back to the debate that prompted this,
if your great^n granddaughter has diverged to the
extent that neither she nor her fellow people are
called "Homo sapiens", you wouldn't really look
back and say that Homo sapiens went the way of
the thylacine. |
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In the end it's all semantics and hot air, but it
becomes important when someone says "99.99% of
all species to have lived are extinct, so that's the
way humans will go". |
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Species 'rebounding' (or 're-evolving' by convergent
evolution) is sort of a seperate issue. |
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What I'm arguing is that evolution should be
viewed as the same way as we view the ancestry
of individual people. My great^5 grandfather
Merrydick and his brother Orsten are both extinct.
But Orsten is more extinct than Merrydick
because, in a triumph of heredity, he's my great^5
grandfather, whereas Orsten (wisely) died without
bearing fruit. |
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So, Merrydick and Orsten are both extinct, but
Orsten is the extincter of the two. |
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To put it another way, if you managed to bring an
Australopithecus and a Neanderthal back from the
dead, the Australopithecus would say "Wow, we've
really made that bipedalism thing work, haven't we?"
whereas the Neanderthal
would say "Oh bugger, and we thought it was all
going so well." |
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Yes (although I did say 'ignore the speculation about
interbreeding'). All sorts of scenarios are possible,
and will have occurred. |
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But I still contend: there's an difference between a
species which is a dead-end, and one which wasn't. |
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//Is it true to say that their common ancestor (habilis) went extinct in the same sense that the Neanderthals went extinct?// |
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I didn't say it was. In that case you have a speciation event leading to two species (Neandertal and Sapiens) but in both cases it was probably a gradual evolution of isolated populations, so neither experienced true extinction, although one of the lines later did. |
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//but we would look back at the fossil record and call two or more species, even if we had difficulty partitioning them; we'd still say the original species was extinct// |
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I would suggest that this indicates a problem with our definition of species. |
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//And I am not suggesting that evolution is a smooth, continuous process; therefore we often see distinct species, and only rarely find the intermediates// |
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I would suggest that our definition of a species is heavily influenced by what we find, leading to observer bias. It's not so much that we don't find intermediates as that we define a given species by the fossils most likely to be recovered, and consider gaps to be the intermediates. |
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This may result from various things, including the possibility that the intermediate species is just less likely to leave fossils owing to a change in environment. |
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// so neither experienced true extinction,
although one of the lines later did.// OK, we
agree on that. I was focussing on the common
ancestor (habilis), which (by my 'definition') didn't
become extinct in the strict sense. |
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//I would suggest that this indicates a problem
with our definition of species// Yes, certainly,
but again that's a horse of a different feather. |
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//our definition of a species is heavily influenced
by what we find// Yes, that too, of course. |
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hmm... what's that buzzword used to mean "fucked over" ? That would fit. |
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//"Oh bugger, and we thought it was all going so well."// [marked-for-tagline] |
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It would be useful to have a different term, but
the
trouble is, when would you have a firm basis for
supposing that one thing has happened and not
the
other? I also think there are many examples of
genuine extinction, for instance creodonts and
Australopithecus robustus, as opposed to other
Australopithecines which did leave descendants. |
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Also, well yes, we might evolve, but why would we
evolve into anything that matters to us, i.e.
anything which is intelligent? Isn't it possible, for
example, that we might survive as a transmissible
pathogen on other species or tubular brainless
things at the bottom of the ocean? |
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//transmissible pathogen on other species// An
*intelligent* transmissible pathogen on other
species? Might not differ all that much from our
present phenotype. |
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(Just quibbling. Another case where it's hard to tell
if one thing has happened and not the other. Your
point is sound.) |
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//the trouble is, when would you have a firm
basis// |
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Well, nothing much is ever for sure in evolution.
However, we have fairly good palaeophylogenetic
trees, in which "extinct" species are placed in
relation to others. They're very far from complete
or correct, of course, but they're the best we can
do. Thus if, on the current interpretation of
human evolution, Australopithecus afarensis lies
on the path to humans, its not "extinct" in the
same way that, say, Homo neanderthalis (which,
crudely speaking, is the terminal point on a
branch) is "extinct". |
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Even though there will be lots of uncertainties,
and the status of species will change as we learn
more about their relationships, these details are
almost secondary to my broader point. This
broader point was that it's wrong not to
distinguish between a "dead end" species and one
which went on to give rise to a successor species. |
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There was a last thylacine who died without
offspring; there was never a last Australopithecus
who died without offspring. That's the
crystallization of the idea. |
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//would we evolve into anything that matters to
us, i.e. anything which is intelligent?// In a
sense, that doesn't matter, because if we evolve
into something non-intelligent we won't really be
in a position to care. |
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But [19thly]'s point was that that eventuality ought
to count as extinction. Or might be held to ought
to. |
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Well, many (if not most) extant parasites have
descended from free-living organisms. I guess you'd
call it an evolutionary demotion. |
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//In a sense, that doesn't matter, because if we evolve into something non-intelligent we won't really be in a position to care.// |
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Wow, maybe that explains why I just can't be arsed about many things... |
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We're all just multi-celled extensions of bacteria, placed here to host them. |
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//demotion// Odd, that. In societies, evolution
into a parasite can be associated with either a fall
*or* a rise in
status. |
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// We're all just multi-celled extensions of bacteria,
placed here to host them. // |
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Now that's a theory I can get behind. |
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Lactobacillus Bulgaris. You're only multicultural if you eat yoghurt. |
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// Homo habilis then evolved into Homo heidelbergensis, which then evolved into Homo sapiens // |
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{MB], we have something to tell you in private about Black Monoliths, which you may find a trifle upsetting to your view of your world and its "history". Please sit down in a comfortable chair, grasp the flagon of Single Malt Whisky being proffered by the flunkey, and take an number of very deep breaths. It won't help, but you go a very amusing colour when you hyperventilate. |
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By fortuitate coincidence, I am already seated in a
very comfortable chair. A flagon seems a trifle
excessive, but I do have a generous glass of
Highland Park '58 (I don't normally bother with the
cooking whisky, but I didn't have the heart to send
old Meniscus back down to the cellar again). |
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Oddly enough, the intercalary twin was recently
troubled by what I believe you call a 'hive mind'.
It was only when he started falling over more than
usual that he realized that the little blighters
had chewed off the middle six inches of his
wooden leg. Permethrin, apparently, was the
most convenient solution. |
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