The Knudelfish and the First Frenchman: Part 1

Post of the Month: August 2002

by John Wilkins

Subject:    Re: 15 Answers to Creationist Nonsense
Newsgroups: talk.origins
Date:       August 26, 2002
Message-ID: 1fhimok.18hnws21useeb4N%wilkins@wehi.edu.au

Dick <dick@christophers.net> wrote:

> On Sat, 24 Aug 2002 22:02:18 +0000 (UTC), "Simplicius"
> <jmckendry@attbi.com> wrote:
>
> >In article <sclfmus5nesa6hquqoihp0sp6jg862lbsg@4ax.com>, "Dick"
> ><dick@christophers.net> wrote:
...
> >> You may have, but the several people telling me I was wrong believing
> >> Darwin had denied Speciation were more wrong than me, and didn't bother
> >> to find out Darwin wrote more than Origin of the Species. I have yet to
> >> read an explanation of Speciation that shows how an evolving life can
> >> replicate once it makes the step beyond being able to reproduce with its
> >> ancestry. Can you provide any citations?
> > This is the first-Frenchman question again: who did the first Frenchman
> >speak French with? The canonical and correct response is that individuals
> >don't evolve, populations evolve. You don't get an individual first
> >Frenchman, you get a whole generation, all speaking French. In species
> >terms, you don't get a single instance of a new species springing up in
> >the middle of its ancestor species. Rather, one group of the original
> >species moves to one side of the hill and another group moves to the
> >other side, and each group develops according to the variations that
> >occur within its breeding population and the selections operating on
> >those variations. Both the variations and the selection pressures will
> >be different in the two populations. Pretty soon the descendant
> >populations will be sufficiently distinct that they can be called
> >different species.
...
> >
> >John McKendry
>
> John, when you produce a mule, it cannot replicate. You can produce a
> male and female mule and still not produce viable offspring. You can
> cross two other species and make all the mules you want, but that is
> not speciation as I understand it.
>
> If you separate into two groups a single species, and each is
> physically unable to intermingle, then you provide a chance that each
> group will mutate uniquely. Or, an individual in each group can
> mutate uniquely. It really isn't necessary to have two groups, for
> once an individual mutation occurs, one has a potential mule. Where
> does the mutant find a partner that can produce a viable offspring?

First of all, not all hybrids are mules (and for that matter a few mules have been able to backbreed into one of their ancestral species, which is a way that genes can cross the species "barrier"; it's common enough to deserve a name: introgression). Hybridisation is a major source of evolutionary novelty.

Second, it is not true that a mutation makes the bearer infertile with its conspecifics. You carry novel mutations; so do I. Yet in my case at least I have been able to interbreed with organisms that don't carry them. One organism, really (in case my wife is listening).

Think of it like this: organisms do not have a can/cannot-breed switch that like a lock and key either works because they are the same or fails to because they are even slightly different. Instead, there is considerable slop. I think of it as "reproductive reach", and it varies according to the species. Ferns can interbreed with almost any other fern, ducks will interbreed with other species of ducks, camels and llamas can interbreed despite being separated for a long time, horses and donkeys can almost interbreed, and cheetahs will interbreed only with other cheetahs. There is no hard and fast rule about the degree of difference that makes the reproductive reach work or not.

So, here's our little knudlefish, or whatever, and it has some new genes. A mudslide causes the knudelfish, or whatever, population it is part of to be separated from the rest of the knudelfish, or whatever, populations for a long time. It is still within the reproductive reach of some, if not all, or the others in its population, so that gene goes throughout the population, perhaps to fixation (ie, becomes the only one at that place on the genome in the population).

Over time, other knudlefish, or whatever, in that population also have new mutations, or perhaps they have genes that go extinct in the main populations for whatever reason, but not in this one. Add all these up, and after a time, you get kniddlefish, which are perhaps just beyond the reproductive reach of the original knudlefish (or whatever). This is demonstrated by another mudslide that rejoins the two populations - they do not successfully interbreed, or perhaps they do, but the hybrids are not as successful or viable as the "purebreds". We now have a new species.

In "geological time" (between the two mudslides) this is a rapid process. In knudlefish (you know) time, this is a gradual process, and at every step, knudlefish - or whatever - are able to find mates they can happily reproduce with, even though they are carriers of a new gene. It is the accrual of changes that changes knudlefish to kniddlefish.

Now, reproductive reach is a vague thing. In some organisms (e.g., flowering plants) a new species can occur in only a couple of generations through hybridisation. In other cases, chromosome changes can cause new species in a few generations. All that is needed to genes to form new species is a flow of new genes into the populations. Speciation (which has been observed to occur - boundless refs upon request) is something that happens to populations, not to individuals, and anyway, biology is more complex and plastic than you think.

--
John Wilkins
Sweet Analytics, 'tis thou hast ravished me [Marlowe's Faust]

[Return to the 2002 Posts of the Month]

Subject:    Re: 15 Answers to Creationist Nonsense
Newsgroups: talk.origins
Date:       August 26, 2002
Message-ID: aisaak-2608022039160001@pool-141-157-185-36.bos.east.verizon.net

In article <pqclmukko8acjhabi1k0v686klsl21jn3p@4ax.com>, Dick <dick@christophers.net> wrote:

> On Sun, 25 Aug 2002 20:09:53 +0000 (UTC), TomS
> <TomS_member@newsguy.com> wrote:
>
> > Has anyone brought up the standard analogy yet? The analogy of
> >the French language being a descendant of the Latin language? How
> >did the first speaker of French talk to anyone in French? (And who
> >did s/he learn French from?)
>
> Yes, several. As with any analogy, it is useful if the concept is not
> clear.

And the analogy obviously failed, since the concept is apparently still not clear to you.

> I understand the concept, but in learning a language there is never a
> go/no go condition. The vocabulary can grow from 0 to whatever upper
> limit, one step at a time. A critical vocabulary never appears. Sign
> language can always fill any void, there for the test of
> communication/reproduction is never failed.

From this it would appear that you have completely misunderstood the point and also that you don't seem to understand how languages work particularly well. It is a very good analogy, though, and worth repeating -- their are minor differences beween biological speciation and linguistic differentiation but none of them affect the point being made.

I have no idea what you mean by a 'critical vocabulary'. The point of the analogy with language change is that a language will change over time such that it will eventually be incomprehensible to its previous speakers. However, the changes will be gradual enough that they will not affect communication between adjacent generations.

That speakers of two languages might be able to compensate for their lack of a common language in various ways is irrelevant (though I suspect you would do well to learn a bit about 'sign languages' before bringing them into play -- a sign language is not a compensatory device; it's a full blown language).

As for the 'go/no go condition' which you speak of, if I am correct in interpreting you, divisions between languages are no different from divisions between species in this regards.

To take a concrete example, let's just consider English. The history of the English language is typically divided into three broad periods, which for the sake of this analogy, we might view as roughly equivalent to 'species'.

Encyclopaedias often give very precise-looking dates for these periods: The Old English period runs from 449-1066, the Middle English period from 1066-1509, and the Modern English period from 1509-present. These dates, however, are incredibly arbitrary and most college texts on the subject will shy away from them.

If you look at progressively older texts, you will find them progessively more difficult to understand. There is no point, however, at which the language miraculously and instantaneously changes.

Just compare the following:

"Now is the winter of our discontent,
Made glorious summer by this sonne of Yorke:
And all the cloudes that lowrd vpon our house,
In the deepe bosome of the Ocean buried."
- Shakespeare

"A knyght ther was, and that a worthy man,
That fro the tyme that he first bigan
To riden out, he loved chivalrie,
Trouthe and honour, fredom and curteisie."
- Chaucer

"Ich was in one sumere dale,
in one suthe dighele hale,
iherde ich holde grete tale,
an hule and one nightengale."
- (Nicolas of Guilford??)

"Hwaet! We Gardena in geardagum,
theodcyninga thrym gefrunon,
hu tha aethelingas ellen fremedon."
- (anonymous -- Beowulf)

The same applies with respect to species over time -- the boundaries are fuzzy; there is no 'go/no go condition' as you put. As differences between populations (whether these be populations separated by time or space) become greater, their ability to reproduce becomes less. It is not the case that some organisms breed perfectly until a certain number of genetic differences accumulate at which point they suddenly cannot breed at all.

Rather, as genetic differences accumulate, organisms will be less likely to be able to successfully breed -- this means there will be a greater number of unsuccessful fertilisation attempts, a greater number of unsuccessful pregnancies, a greater number of offspring that don't survive to maturity. Eventually the differences will become so great that reproduction won't be possible at all, but deciding where exactly that point lies will be an arbitrary decision as the species boundary is a fuzzy one to begin with.

> We know, in the case of humans for instance, lots of mutations can
> take place and still have reproduction. I don't know of any human
> stock that cannot breed with another. Yet, humans have changed in
> different climates, altitudes, faced with different predators, but the
> changes never stopped reproduction.

So what? That merely shows that humans are sufficiently genetically uniform to satisfy the biological definition of a species -- of course different populations will have genetic differences, but that's true of all populations; not just those which have undergone speciation. [Note: Don't forget that humans are very genetically homogeneous relative to most species, and have been for some time. --Ed.]

<snip>

--
André G. Isaak
n.b. there are no monotremes in my email address

[Return to the 2002 Posts of the Month]