No, an average one-year old wouldn't be able to do that.
According to the book J. and I gave you, "Teach your Child" (red cover in case you will be looking for it and dusting it off :P), a one-year old would be able to stack two regular blocks on top of each other. A two-year old would be able to stack four regular blocks on top of each other.
The book doesn't mention Duplo blocks, but because those are harder to stack on top of each other, you could conclude Nathan may either be very handy, or that it was coincidence. Time will tell...
Early
No, an average one-year old wouldn't be able to do that.
According to the book J. and I gave you, "Teach your Child" (red cover in case you will be looking for it and dusting it off :P), a one-year old would be able to stack two regular blocks on top of each other. A two-year old would be able to stack four regular blocks on top of each other.
The book doesn't mention Duplo blocks, but because those are harder to stack on top of each other, you could conclude Nathan may either be very handy, or that it was coincidence. Time will tell...