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Waiter, there's an ammonite in my chicken (Re: Sauroparental care)
Either I joined the thread late and therefore don't know the context, or
some list members have been getting in to the holiday punch early!
"Amniote", folks. It's "amniote". ;-)
<pb> (who'll be sippin' the stew in due course)
On Tue, 23 Dec 2003 14:02:11 -0500 Graydon <firstname.lastname@example.org> writes:
> On Tue, Dec 23, 2003 at 01:21:13PM -0500, John Bois scripsit:
> > On Tue, 23 Dec 2003, Graydon wrote:
> > > On Tue, Dec 23, 2003 at 08:46:16AM -0500, John Bois scripsit:
> > > > On Mon, 22 Dec 2003, Graydon wrote:
> > > > But the bracket is important. How do you rate such brackets?
> > > > imagine the bracket is strong enough for you to agree that
> > > > sauropods had red blood without any direct evidence.
> > >
> > > That's not the bracket. That's 'common descent from an
> > > ancestor'.
> > I thought the bracket in this case was, then, ammonites and
> Birds *are* ammonites. Haemoglobin as the means of oxygen transport
> like the tetrapod skeleton, ancestral.
> A bracket is a way of saying something about likelihood when you
> have any evidence. In the case of 'red blood', we do have evidence
> the genes that code for the stuff; they're pretty much the same
> everything that bleeds red. That means it evolved once and got
> into descendants. Supposing that sauropods evolved a novel form of
> oxygen transport then violates parsimony.
> > > Talking about the phylogenetic bracket to set a rough, doubtful,
> > > on probable behaviours is a very different thing that looking at
> > > descent for basics of biochemical composition, and much less
> > Common descent is what makes any bracket relevant. And, at some
> level, at
> > some future time, hypotheses regarding the biochemical nature of
> > investment may be testabl (e.g., shared parental investment genes
> in both
> > birds and crocs).
> That's still not evidence they made it into sauropods (or
> ornithsicians). They'd have to be essentially the *same* genes,
> is monumentally unlikely given that the range of parental care
> behaviours is large.
> > > > Parental care isn't as strong of course--but it _is_ strong.
> > >
> > > It's a very tenuous inference.
> > How is it tenuous if within the bracket it is almost universal?
> Because you're ignoring size effects; "parental care" isn't an
> independent variable. Smaller creatures make relatively larger
> reproductive investments. So *all* modern birds are bad examples of
> choice space for sauropods.
> Crocs are similarly very small by comparison, and don't have
> care; they have a variable degree of nest defense, and some
> intermittent care of hatchlings.
> > > Parental care has a cost. This cost is not obviously, or
> > > lower than the cost of producing lots and lots of offspring.
> > This is what we are discussing--but how do you respond to the fact
> > its universality.
> By pointing out that it *isn't* universal?
> > > It works for turtles in an aquatic environment with a greater
> > > proportion of predators than a terrestrial ecosystem; why
> > > it work for sauropods?
> > Then why do they scramble for the water? Predation must be
> > lower--locally, at least.
> They scramble for the water because that's where they can move and
> I suspect.
> Also note that current sea turtle populations are very low, compared
> historical numbers; this is because people eat them. This makes the
> effect of predation pressure worse.
> > > All you have to do is to assume that the number of predators is
> > > little too low to always get a perfect kill off. That's very
> > > if the egg laying is seasonal, because the predators have to
> > > through the lean season, and can't carry maximal numbers to the
> > > hatching.
> > On the contrary, a big crop of unprotected growing sauropods
> > support a few predators w for a number of yewars.
> And it probably did, but that's not the point I was trying to make.
> You have an episodic food source. It can carry the number of
> that can survive through the *dip*, not the peak. (Consider
> and the arctic weasel population. It's the dip, not the peak, that
> constrains the weasel population.)
> If the peak is sufficiently large compared to the dip that the
> supply is flatly incapable of eating all of the peak population of
> sauropod hatchlings, the R strategy will work fine.
> > > > Firstly, "R-strategy" is only a relative term. To a crab
> turtles look
> > > > like K strategists. Secondly, as argued above, if turtles
> stayed on
> > > > land they would not survive.
> > >
> > > They get eaten in the ocean, too.
> > They scramble to get in the ocean. This is a survival tactic,
> right? I
> > don't imagine such a trait could survive if the rush to the ocean
> > pay reproductive dividends.
> It's a tactic to get where they can move and eat; they're sea
> they have flippers. They would rush to the ocean without the
> > > The available fossil sauropod clutches have very large numbers
> > > eggs in them. That's not what a trending-K strategist egg layer
> > > observed to do, that's what a trending-R strategist egg layer
> > > observed to do.
> > 20 eggs is R strategy only in a relative sense. One can't
> > overestimate the cost of courting, mating, traveling to nest
> > etc.
> Sure one can. Those are all real costs, but they're not
> high or even high-risk.
> > At the very least, you can't make a statement that for sauropods
> > were cheap, plentiful, and not limiting. I mean, you can make
> > it...but it doesn't have evidenciary support.
> Sure it does. Mass. A clutch of eggs that represents 50% of the
> weight of the bird that laid them is a huge investment. A clutch
> eggs that represents 0.5% of the weight of the sauropod that laid
> is not a major investment.
> > > Elephants are compulsory K strategists because they are mammals,
> > > one, and for two, they aren't wildly successful,
> > > they have narrow reproductive margins and deal very badly with
> > > introduction of novel predators, as evidenced by North
> > > (and the rest of the world's) lack of mammoth.
> > The novel predator is man?
> Elephants don't have much reproductive elasticity; one female
> has a maximum lifetime number of offspring around ten.
> Postulating 20 eggs per clutch, 1 clutch a year, and the same 40
> reproductive life, the female sauropod has 800 potential offpsring,
> probably for a smaller proportionate energy investment.
> There is no particular reason to suppose that the sauropod clutch
> that small, or that egg-laying was that infrequent.
> email@example.com | Uton we hycgan hwaer we ham agen,
> | ond thonne gedhencan he we thider cumen.
> | -- The Seafarer, ll. 117-118.
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