Mammal Evolution

[NavajoEverclear]

Mammals are cool---- how did they evolve? I've tried to find info. from google, but it seems to be unsure.

[BrainMan]

By "how" are you looking for a specification of the environmental forces, genetic processes, and so forth? Are you looking for the (hypothesized) line of decent leading from earlier animals to the mammals? Something broader like the line of decent from bacteria to mammal?

[NavajoEverclear]

Oh. I was thinking of line of decent, but it would be interesting to hear about those other factors you mentioned.

[jpat1023]

Read a book on evolution.

[NavajoEverclear]

Thats about the ten millionth time i've been told that. I don't understand why someone cant just tell me. Ok fine i swear i'll get a book. Maybe a few. If i don't find what i want i'll eat you.

[NavajoEverclear]

OK sorry about that outburst. If its not there thats ok and i wont kill anyone.

[greg1917]

Read a book on evolution

That was constructive wasnt it? Dont bother posting crap just because you cant give someone an answer.

[mooeypoo]

NavajoEverclear:

I can't tell you the entire process, most of it because I don't quite know the ENTIRE down-to-the-last-molecule-evolving process, but I can tell you it's a lot about random occurances.

Say, 100 things happen at once (we're talking about "mulecules combining" and "organizms developing" as the 'things').
Only about 30 survive the environment. The rest - sicne they were more or less accidental - just don't survive, and die.

Now you have 30 different "species" of organisms, that change and change and create more variations. Most of them just DIE because they don't fit their environment, while others continue to keep changing and adapt.

Why are they changing? because the environment is also changing, and they're transforming to such organisms that require more and more changes and so on. It's like if you take a cell, it requires only a few basic things to survive - but if that cell aventually becomes an ameba, that organism requires much much more to survive, so it changes it's environment and so it needs to change more and so on and so on.

It's *really* simplified, and please don't take me on the small details here, but its just trying to show that the entire evolutionary process is infact quite a case of trial and error.

Evolution doesn't "KNOW" what to produce. The organisms are trying to fit themselves to the changing environment, and if they "failed" - or if the environment is changing too rapidly, then they wil just not continue onwards - they will DIE.

So aventually what you have is creatures that are perfectly fitted to their environment.
And some other mutations that might die and not "continue" the evolutionary process of those animals...

I hope that helped a bit, although it was really simplified..

By the way, I seriously suggest you look up a bit of more extended info on the net about evolution - it would be much more extensive than anyone on the forum answering you, and would give you the basis that you might need to ask more precise questions.

These are two REALLY good ones I found (both in the same site but they're REALLY good):
http://www.pbs.org/wgbh/evolution/
http://www.pbs.org/wnet/nature/triumphoflife/

hope I helped.

~moo

[Skye]

Mammals are thought to have descended from a group of carnivorous reptiles called therapsids. The differences between mammals and therapsids are arbitrary, and the therapsids as a group probably had some of the features that mammals today only had, like suckling young, and maybe things like fur and some temperature regulation. These things are hard to determine from fossil records though, and the line drawn between therapsids and mammals is based alot on the jaw and teeth, mammals have more complex molars and a particular hinge arrangement of the jaw. Some mammalian features, notably the placenta, probably developed over a period of time. Marsupials are probably an intermediate in terms of placental evolution. Monotremes may be a completely seperate lineage that also descended from therapsids.