Monday, July 14, 2008

Questions about evolution and origins of life

Here are a couple questions I have for scientists who study evolution. Let me preface this with a couple things: 1. I have no horse in this race; 2. It matters to me what the truth is, but I don't care what turns out to be the truth. With that, here are my two questions:

1. Given that some scientists are now claiming that life might have started as some form of RNA-based organism, why are there no longer any RNA-based organisms, especially if that's how life started? Even if they had died out, shouldn't they be able to start up again, if that's how life got its start? Wouldn't that be a prediction of the conjecture?

2. If evolution occurs through "transitionals" -- for example, the flounder transitionals have been found

should we not be able to find examples of organisms that are obvious living transitionals? Like the Picasso-fish above, you can see in advance what it's going for. Then scientists could make educated guesses about where a particular type of organism is headed and why. Sure it takes thousands of years for the changes to happen, but they might learn something by looking for a transition in progress.

Regarding transitionals, it seems strange to me that most animals in existence appear to be not in a state of transition. They seem to be fully developed and living statically in whatever is their native environment. Shouldn't evolution "speed up" in some sense over time as more and more organisms compete for resources?


Blogger Chris_topher said...

Click read more to get the whole article that should help see the argument against the flatfish's evolution

7/14/2008 9:58 PM  
Blogger carnaby said...

Very interesting, Chris. Thanks.

7/14/2008 11:02 PM  
Anonymous Gideon7 said...

The flounder's eye gradually moves to the other side as it ages, if I remember correctly. Who is to say that the other fish shown simply died as fossils before the eye finished moving?

The flounder is a bottom feeder. The advantage of having two eyes facing upwards while laying sideways to spot predators is obvious. Assuming the other 'species' are real (and not just dead juveniles) how does an eye partially raised, say 45 degrees (figure 2), help survival?

7/22/2008 12:26 AM  
Anonymous Nomen Nescio said...

those transitional flatfish were not "going for" anything whatever, excepting of course survival and reproduction. evolution is not a directed process, it doesn't have any goal "in mind", in fact, it doesn't have any "mind" to begin with.

had we been able to examine those transitional semi-flounder when alive, they would not necessarily have seemed transitional in the context of their lives. they likely didn't live quite like modern flatfish do; they may have spent less time flat against the bottom waiting for prey, and their posture was likely less flat when they did use it. in one sense, it had to be that way, because of that partially-moved eye; in another sense, that lifestyle made the eye not need to be more than partially moved. although, even then, likely ones with more moved eyes --- ones that could lie flatter, for longer --- managed a little bit better, and that might even have been measurable, had we been there.

modern transitionals? everything that reproduces is a transitional, between its ancestors and its descendants. whatever lives and doesn't reproduce is a line that's going extinct. i'm in the latter category myself, although my brother's a transitional.

for a specific example, one might mention the pit vipers. those pits on their noses are lined with infrared-sensitive cells. they're very primitive camera-obscura eyes, and might over time become genuine camera eyes, assuming better infrared detection is a selective plus for them. that's not an obviously suspect assumption, and some estimates have it that camera eyes can arise from light-sensitive patches of skin in a few tens of thousands of generations, so a four-eyed vertebrate species may be very soon to come in geologic terms.

more fancifully imagined, penguins might be transitional towards a fully aquatic avian species. that'd be a much more difficult transition, since they'd have to re-jigger their reproduction, and it's far from obvious where the selective pressures are pushing them in that regard. still, the whales went there, so it'd be foolish to call it impossible.

but generally, living species seem to be quite well adapted to their environments because they are. if they weren't, they'd be dead --- or outcompeted, which is dead. only in exceptional cases of the environment changing faster than a species can keep up with (or a species migrating into a dramatically different environment) would you expect to see noticeably ill-adapted lifeforms around. in such cases, whether such species will be around for very long is not at all clear.

sabre-toothed large cats have evolved several different times over the ages. they never stick around long; the oversize teeth are an adaptation for taking very large game, and herds of suitable large game animals aren't very ecologically stable it seems. climate changes, grazing changes, the herds move away into climates the cats can't deal with or simply die off --- and then, poof, no more sabretooths. if the buffalo had roamed for long enough, and humans hadn't objected too much, then perhaps some descendant of the mountain lion would have grown oversized incisors in some alternate future --- but that didn't happen.

on the other paw, invasive species are species that have migrated into environments different from the ones they originally evolved in yet done very well for it. zebra mussels weren't found in the Great Lakes until quite recently, so it'd be a bit odd to say they're "well adapted" for an environment they only very recently encountered at all, but there's no getting them out of there now. give them sufficient time, and they'll likely adapt to this new environment and become something no longer a zebra mussel, yet just as impossible to ever get out of the Great Lakes.

7/22/2008 12:51 PM  

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