[PatrickHenry]

Then you can't understand that the program output is exactly what I program it to be. No more no less.

I don't think so, unless you tamper with the results. The reason I asked "if you can program a model giving the same result as the one in the article, with the same mutation and migration rates, but with a starting point of only 6,000 years in the past" is because I don't think you can.

As I said, I'm not a programmer. But I've done modeling with a spreadsheet. If I know the starting quantity (say $100K, the amount invested), and the ending result desired ($1 million), I can diddle with the variables (rate of return and time) until I get the desired result. But I can't do that if the rate of return and the time are already known -- not unless I delve into the bowels of the underlying software and produce a false result.

In the case of the article, the factors are known (starting point, ending result, and the rates of mutation and migration). The input was known. The output was known. What was missing was the model itself. The challenge was to create a model which fit the data. That's a very specific challenge, and no matter how good a programmer you may be, it doesn't mean, as I think you're claiming, that you can conjure up just any old model and make it fit the data. You may be a great programmer, but I don't think you understand what the article is all about.

[Mr. K]

you nailed it- they created a model to fit the data, then showed the output and said "see?"

It is the same thing you did with your spreadsheet- you knew what outcome you wanted and so made a modle that gave you that output for your starting input.

I laff my ass off when I hear on TV someone say "thats what the computer model says"

The closest thing to an exception is weather modeling which is rarely able to predict anything past a few days- and I can do that myself looking at the prevailing wind patterns