So, my friend and I were discussing macroevolution. Basically, she doesn't really believe (but would if solid evidence was found), and I do. She brought up the fact of how she doesn't see how an organism could turn into a completely different organism (she also believes that the Earth is only about 2000 years old, while I believe it is 4.5 billion). She didn't see how there could be "missing links" between mammals and reptiles, or reptiles and birds. I took one of my beliefs into a diagram and tried to explain how different classes (mammals, reptiles, and birds) could evolve. So, how dinosaurs and pterosaurs were separate classes perhaps, and then somehow merged together to form modern birds. Or how mammal-like reptiles separated into mammals and reptiles. I haven't completely developed the thought, but is that possible? Has anyone thought of it before?

Hi Carrie,

A bit hard to anwer this since - from the perspective of an evolutionary biologist micro- and macro-evolution are the same thing. Creationists often seek to make a distinction but in scientific terms this has no basis in fact. We do however sometimes refer to microevolutionary change (as change we see across generations within a population, or sometimes divergence between populations over short timescales e.g., several generations to several tens or hundreds), and macroevolutionary patterns (the patterns seen among species or higher level groupings). The distinction is not one of process - its all just evolution - but timescale. We can often watch "microevolutionary change" in real time, but we can't -by definition- watch "macroevolution happening" because it's a consequence of long period of microevolution. Not sure if that is clear - hopefully.

Maybe a sports analogy would help (maybe not but heh - I'm excited about the rugby world cup!). People started playing football (soccer) a long time ago, at some point some guy (allegedly) picked up the ball and started running with it (rugby). From there rugby developed its own rules in the UK, eventually splitting into two forms (which kept on developing into rugby league and rugby union). At the same time some rugby players ended up in N America and american football started to develop, although in Canada the rules it develped in slightly different ways etc etc

So is this microevolution of a single sport football? Or do we look at where we are today and say there are X number of different sports (=species) and macroevolution has happened. I think the latter is reasonable, but there is no sudden point of time or development in which we jump from one sport to another (or rather not one everyone will agree on... hence the constant arguing over macroevolution!)