The Lone Ranger

DavidH:

I mean no offense, but it was conclusively demonstrated long ago that acquired characters cannot be inherited. Therefore, it would never have occurred to me that someone could think I was advocating Lamarckianism in my post. Sorry if it was confusing.

Cheers,

Michael

Oolon Colluphid

Just to make it clear to David why Lamarckism is stupid and that nobody advocates it: the vast majority of characteristics an organism acquires during its lifetime will be injuries. Children of one-legged people are two-legged. The acquired characteristics do not code back into the DNA of gametes, and so are not passed on. Only changes in what is passed on -- DNA -- affect the phenotype of subsequent generations.

Ref bipedalism: whatever the selection pressures for uprightness may have been, it matters not the slightest how much any individuals twisted (or whatever) their backs. Nobody means that these twisted backs were passed on.

Those individuals that were phenotypically predisposed to getting more upright had an advantage over those that couldn’t. So they left more descendants, who inherited the ability/morpholgical difference that let them do so too. That is how characteristics spread through populations.

Just to reiterate for emphasis: lineages evolve, not individuals.

Cheers, Oolon

MrDarwin

It's true that we know precious little about the evolution of bats and their wings. But it's safe to say that bats never had "defective wings" any more than flying squirrels, flying lemurs, or any number of any gliding animals (including frogs and snakes) have "defective wings". We have numerous living examples of creatures that are halfway to flying.

However, we can look to a similar case--the evolution of birds and their wings--and see from the fossil record that they never went through a stage with "defective wings". What they did go through was a stage when the wings had a dual function as forelimbs (in fact the forelimbs of the earliest birds are almost indistinguishable from the forelimbs of several dinosaurs).

And yet there are many birds that are not woodpeckers that are able to pierce the bark of trees to get at burrowing insects; they simply have to work at it, over and over. Woodpeckers have simply gotten better (and faster) at it. Pecking isn't even an issue because so many birds do it (have you ever watched chickens eating?) I'm afraid I really don't see the problem here.

"Fact"? Says who? You mean the old chestnut about "we only use 10% of our brains"? I suggest you do some research on this one and then get back to us, either with something to back up your "fact" or an admission that you don't know what you're talking about.

(Edited because I can't resist asking The Apologist what part of his brain he would be willing to do without!)

[ May 31, 2002: Message edited by: MrDarwin ]</p>

Oolon Colluphid

Well I think that about wraps it up.

I wonder if Apologist will pop back to say thanks for the info, or if he has any other questions?

Oolon

Lady MacDuff

In regards to Apologist's "which bat?" question, I came in late but just wanted to add my two-cents on bat flight...

Since there are thousands of kinds of bats in the world, and many of them feed on different things, could it be possible that flight evolved separately in the different populations for different reasons? For example, ground-dwelling insectivorous bats could have greatly increased their foraging volume by increasing the length of their arms and developing the "web" between their fingers. I read of a study done that showed that insectivorous birds used far fewer calories to jump and forgage than by simply running, which also meant that the higher they could jump, the more massive the foraging benefits to them.

As for carnivorous bats, I would think that they would also benefit from longer arms and flight if they fed on birds or fish.

There are some bats that use nectar for energy, and one could assume that the ability to jump higher with greater stability from longer forearms would enable them to reach previously inaccessible flowers.

Duvenoy

Bats rock! What amazing amimals! And arguably one of the most efficent fliers in the world.

An insectivorus bat catches it's prey, not with it's jaws, but with the membrane between it's hind legs and tail. It will scoop up and trap the insect like a catcher's mitt, then eat it on the fly. A fishing bat uses the claws on it's hind feet in the same way.

The social life of many species is also remarkable, but this is not the place to study natural history, alas. I'd suggest Googling it.

It is a pity that more fossils haven't been found. I would love to know how and from what bats evolved.

d

Clutch

One of my favourite memories is of evenings spent on the balcony of a guest house near the China/Burma border, drinking cold beer, smoking eucalyptus cheroots, and watching the bats fly. Man, those fellas can turn at speed! I'd just read Stebbins' The Acoustic Sense of Animals not long before the trip, and was fascinated not just by the bats' unbelievable flight dynamics, but by the way their flight showed the evasion tactics of the flying insects they were chowing down on. Better than TV, any day! I wish we had early evening bats around here. They keep the mosquitos down, too.

Duvenoy

Here’s a couple of very good bat sites:

The "http://www.ucmp.berkeley.edu/mammal/eutheria/chiroptera.html", are the second most diverse group of "http://www.ucmp.berkeley.edu/mammal/mammal.html", and are the only mammals ever to evolve true powered flight. The evolutionary origin of chiropterans is still somewhat of a mystery, because the fossil record of bats is scant. Cladistic analyses indicate that bats are most closely related to the dermopterans, such as Cynocephalus, the colugo or "flying lemur" (which does not fly and is not a lemur). The best inference that can be made so far is that dermopterans and bats diverged from a common ancestor about 60-65 million years ago. The problem of the bat flight origin is that scientists are still not certain whether Chiroptera is a proper monophyletic group -- it has been hypothesized that microchiropterans and megachiropterans evolved from separate ancestors, which would mean that flight evolved twice in mammals, and four times in vertebrates! For now, "http://www.ucmp.berkeley.edu/vertebrates/flight/origins.html" researchers assume that Chiroptera is a monophyletic group. This assumption seems to be well supported by very recent analyses of bat evolution.

<a href="http://www.ucmp.berkeley.edu/vertebrates/flight/bats.html" target="_blank">http://www.ucmp.berkeley.edu/vertebrates/flight/bats.html</a>


Bats are the only true flying mammals, with about 925 different species identified. Of all these species, only the common vampire bat is able to maneuver on the ground as well as in the air. According to Schutt (1998), vampire bats can move side to side and backward, similar to a spider. Instead of taking off in flight from the ground, these bats actually launch themselves into the air with powerful pectoral muscles. The force comes from the bat extending its hind knees, leaning forward and using its forelimbs. The bat also invokes its triceps muscle and very long thumb. While the jump only takes about 30 milliseconds, the bat catapults itself about 4 feet into the air. Altenbach (1979) comments, “although a few other species of bats move readily on the ground and some take off from the ground, no other species possess the extreme terrestrial agility and jumping ability of Desmodus”. Once in the air, the transition into flight is basically one fluid motion. Since the vampire bat feeds at ground level, their agility and fast take-off is an amazing advantage.


<a href="http://bss.sfsu.edu/geog/bholzman/courses/fall99projects/vampire.htm" target="_blank">http://bss.sfsu.edu/geog/bholzman/courses/fall99projects/vampire.htm</a>

Enjoy!

d

PS: When I lived in rural VT, I had a small bat box set up. There was room for 20 bats to roost and I had many enjoyable, summer evenings seeing them leave for the night. I used to watch for them to come 'home' in the morning as well.

Lizard

I've learned a lot from reading this thread. Thanks to everyone who took time to respond.

I wonder, though. Has anyone noticed that The Apologist asked some questions, then disappeared? I hope s/he's at least reading all this good info.

Duvenoy

Oolon: "I wonder if Apologist will pop back to say thanks for the info, or if he has any other questions?"

I fear the Apologist has made his apologies and left the party early. Urgent business elsewhere, no doubt. And just when it was getting good, too.

Ah well.

d