Comments on: Why giant sea scorpions got so big

By: Kat

Kat — Tue, 03 Apr 2012 13:14:48 +0000

Hello. I’m wanting to post a comment of your statment of natural selection doesn’t design organisms to cope with events that havn’t happened yet.
It’s just as well. Can you imagine how dangerous it would be for modern day swimmers to go a swim in the sea and get killed by a giant Sea Scorpion. How dangerous it would be for bird life and marine life.
It’s just as well the Megaladon went extinct as well, how life threatening that would be surfers and luxury cruisers.
I don’t think Jurassic should be made a reality either, because it would end up happening just the way it happened in the movie.

By: Nick Gardner

Nick Gardner — Sat, 17 Oct 2009 16:59:51 +0000

http://dx.doi.org/10.1098/rsbl.2009.0700

By: Greg Laden

Greg Laden — Thu, 15 Oct 2009 10:36:50 +0000

Right … wrong reference. Well, I’m on the road so this is going to be hard to fix for a couple of days. Was this a glitch in the automatic reference generation system using DOI? Maybe. Maybe not. We shall see…

Anyway, the paper is the next one over in the same journal.

By: Greg Laden

Greg Laden — Thu, 15 Oct 2009 10:34:27 +0000

travcEvolution can design organisms to cope with variability in the environment.

I think that is right but it remains to be demonstrated to the degree needed to become part of the dogma. In any event, mass extinction events != variability in the environment than can be tracked by N.S.

I have a one liner I like to use in teaching evolution because it get people mad and is as true as any other thing people say about evolution, yet flawed, and is thus a good starting point for discussion: “The ultimate outcome of evolution is almost always extinction.” The body size conundrum you point out is an example of that.

By: Diane G.

Diane G. — Wed, 14 Oct 2009 23:43:18 +0000

The placoderms won.

Endoskeleton beats the exoskeleton in size race yet again.

By: MadScientist

MadScientist — Wed, 14 Oct 2009 17:02:10 +0000

I’ve always objected to the use of the word “design” because evolution doesn’t design anything. If something happens in the environment, say, much higher temperatures, there is no opportunity for evolution to do anything. The organisms that can withstand higher temperatures will already exist and will be the preferred individuals (part of natural selection). So the (single species) evolution necessary to cope would have already happened or else the species goes extinct; in this case the ability to withstand higher temperatures gives an individual an advantage in selection where previously there was no obvious advantage between the individuals.

By: Rob Jase

Rob Jase — Wed, 14 Oct 2009 16:11:12 +0000

I think you’ve stumbled onto something Zach.

By: Phillip IV

Phillip IV — Wed, 14 Oct 2009 16:10:59 +0000

I can’t help but think the paper was poorly titled, as neither placoderms nor eurypterids are mammals, or even tetrapods.

At first they were going to name it ‘J.C. Lamsdell and S.J. Braddy (2009). Copeâ??s Rule and Romerâ??s theory: Patterns of diversity and gigantism in eurypterids and Palaeozoic vertebrates. Biology Letters.’ But the focus group wasn’t too hot for that title – fuzzy animals simply sell a lot better.

By: Zach Miller

Zach Miller — Wed, 14 Oct 2009 15:38:07 +0000

I can’t help but think the paper was poorly titled, as neither placoderms nor eurypterids are mammals, or even tetrapods.

By: travc

travc — Wed, 14 Oct 2009 14:53:44 +0000

A quibble on “natural selection does not design organisms to cope with events that have not happened yet”.

Yeah, very true and important to point out to folks who don’t really grok ToE. But perhaps more interesting to those who do already generally ‘get it’… Evolution can design organisms to cope with variability in the environment. Part of this is a (normally weak) selection for adaptability… a sort of evolution of evolvability. There is an infinite regression… but we are still arguing over wether the first order effects are strong enough to generally matter.

Predatory eurypterids appear to have been pushed by strong-ish selection towards larger body sizes. This decreased their variability and the population’s ability to respond to different selective pressures on body size (and probably lots of ancillary traits). That set them up for a fall when the environment changed, since they traded a lot adaptability for optimization to the particulars of a single niche. The scavengers were more diverse and maintained more adaptability as a group… so they lasted longer.

Hard data would be nice… but it does make a nice story 😉