Macroevolution Observed?

Obviously, since it has.But if it's not happening in a situation where you can constantly observe it, what are the odds that you're going to catch it in the act?

Why? What's the survival advantage of being a nectarine instead of a peach?If macroevolution is true, we should see some things - like many different species of organism based on one general body plan. (Check.) Or a fossil record showing transitional species. (Check.) Or adaption to environment. (Check.)If you want to see an "event" of macroevolution, it's called "speciation". But since evolution is a gradual change you can't expect to observe a lizard turning into a mammal. It's like asking where the foothills end and the mountains begin.

Since the Lincoln Administration is neither observable or repeatable, how can we conclude that Abraham Lincoln was ever the President of the United States?To you, what evidence does it take to substantiate hisorical claims? Somehow I doubt that you have a problem when other kinds of historical claims are made, such as in courtroom forensics (after all, a murder can't be repeated). Just because something happens in the past, or over a great period of time, doesn't mean we can't substantiate it with evidence.

A group of persons from Germany is different than a group of persons from Nigeria. Nonetheless they are able to interbreed.But if you took the group from Germany and put them on Mars, so that there was no longer any circumstance where genes could flow between the two groups, then the group on Mars would accrue mutations until they were no longer able to breed with the group in Nigeria, no matter what. At that point they would be different species. That's macroevolution - new species arising through reproductive isolation.

The thing I think you're missing is that macroevolution isn't an event, it's a result.To illustrate, let's count to ten. 1,2,3,4,5,6,7,8,9,10. Simple, right? Tiny little steps each time, right?Now, where in that sequence did we go from one to ten? We did, right? We started with one, and now we have ten. That's a big change, so where did it happen? The answer is that going from one to ten isn't an event of counting, it's a result of counting.Macroevolution is the result of a process that starts with reproductive isolation and is driven by incremental change over time. Eventually the accumulated change is sufficient that there are two separate species where before there were one. It's macroevolution, apparently, when the two groups pass some arbitrary measure of different-ness. (This ambiguity is why biologists don't generally use the term macroevolution; it's not very descriptive.)

Now you're asking two separate questions. "What causes drastic change" and "what gives rise to new species" are two different questions with different answers.In your analogy, what separates us is the fact that you walked to Detroit (the drastic change stemming from accumulating mutation) and the fact that I didn't go with you (the reproductive isolation).Us being separated didn't get you to Detroit. Reproductive isolation doesn't cause adaptation, of course. What it does cause is noninterfertility. If the populations hadn't separated - if I had gone with you to Detroit - speciation wouldn't have happened, no matter how drastic the change was. No matter how far you go, if I went with you, we're still in the same place as each other.Does that make it any clearer? It's the changes that get you to Detroit. But it's the fact that you went there alone that makes you a new species.