reply to post by Agree2Disagree
Except you're talking about the exact same thing.
What, exactly makes a bird
not a reptile? Technically speaking,
they are. They're part of a broad grouping of reptiles known as
archosaurs - a group they shared with crocodiles, pterosaurs and dinosaurs. In fact the bird and the crocodile have more in common genetically than a
crocodile and a lizard do, because of this.
Let's say you start with a robin. Go back one generation at a time. That robin's parents, its grandparents, its great great grandparents. obviously
each of these birds will be genetically different. You'll start finding those that are phenotypically different after a few generations - different
spot patterns as chicks, perhaps different shade on the breast feathers, longer or shorter primaries, a different tone of song... Then go back down
those robin's ancestry. You'll end up at a thrush (or a flycatcher, if you're looking at a european robin) that looks a lot like a robin,
but also doesn't look a lot like one.
Now that you've found the proto-robin, follow
its ancestors, one at a time. You'll go through the same process of most of hte nearby
relatives looking very similar, with small differences adding up the further back you go. Now you've arrived at something that is very thrushlike,
kind of thrasher-like, and mildly like a mockingbird.
Follow
its ancestors back, and you see the same pattern. Your thrusheringbird's closest ancestors look a lot like it, but the small
differences add up until, look at this, you've found a small perching bird that looks a bit thrasheringbird-like, and just a bit wrarrowcatcher-like.
And so on down the line until you've found the common ancestor of crows, then the common ancestor of toucans, then the common ancestor of woodpeckers
and parrots, s on and so forth.
It's a long line of a lot of birds, but you've gotten there just by tracing the robin's ancestry. At no point in the line does a given bird look
particularly dofferent from its immediate ancestors or its immediate descendants. But the little peculiarities add up.
If you go back far enough, you'll find birds without breast keels, birds with teeth, birds with articulate fingers on their wings, birds without
feather diffentiation, birds without genuine vanes, then "birds" that look awfully reptile-like but with fluffy feathers, then with frizzy feathers,
then with scales...
And still, at no point did you hit a mark where a critter was obviously different from what comes just before or just after.
This perhaps describes "microevolution" just fine. So what of macro-evolution? This is the fake (or, to be generous, perhaps very misconceived)
term. At no point is there a "stop." There is no definitive moment where a reptile stopped being a reptile and became a bird (or a mammal). Instead
you get a steady progression of organisms, each essentially the same as what comes immediately before and immediately after, but with just enough
genetic difference (thanks to both mutation and sexual reproduction) to make many small differences that add up enough that, from the starting point
of a thrusheringbird, the creature a hundred generations ahead of it is quite different from the creature a hundred generations behind it.
So, cut out "macroevolution" and you're left with "microevolution"... And since there is no "macro-" to justify theneed to put a "micro-"
there, all you're left with is evolution.
Of course all this is pretty simplistic, since whatever lies in the robin's ancestry
isn't going to look like a perfect blend of everything
that came after it (there are no wrarrowcatchers, just like there are none of the famed fronkeys) but it makes a decent illustrative point.
[edit on 11-11-2009 by TheWalkingFox]
