Was I weaned too young? Will I have behaviour problems?

Dear George,
I’m sitting here, on the stairs (as you can see in the photo) and left to ponder over my human’s words “that I was way too young” when I was rescued. It seems that my human mummy has this obsession about who could abandon me at such a young age.
The truth is that I can’t remember how old I was but probably I was about 4 weeks old when I “landed” into my humans’ backyard. How did I get there? No one, including myself, has any idea! Based on the comments I hear it seems that I lack some skills that only the biological mother can teach the kittens. Well, I purr-sonally don’t think I miss anything! Actually I think I’m purr-fect! And I live a very happy life! 
So George, why four weeks is “way too young” and “12 weeks is a bit old”?
Is there such a thing as “an appropriate age” for adoption?
A bit confused but otherwise Purr-fect!
CAT Victoria 

Dear Victoria,  
There are two reasons why cats should stay with their mother for about eight weeks minimum (if possible).  One is food. Mother's milk is the best way for them to grow big and strong, though they can take solid food as well from 4 weeks. If they are orphan kittens, most shelters will supplement solid food with special formula milk. 
But cats are very adaptable. If there is no mother, and they are put on all-solid food at four weeks, most will survive.  Feral kittens, that lose their mother, often start hunting earlier than those that still have a mum. They have to, if they are to survive.
The second reason is behaviour. Kittens learn a lot from the mother and siblings. They learn how to play without being too rough. They learn what is good to eat. Kittens brought up with a mother but without siblings may be less sociable towards other cats (we think). They may be more aggressive to other cats. 
If they are bottle fed by a human, it is said that they think they are human. They have difficulties mating. The other possibility - and research is under way on this - that they cannot tolerate frustration.
A mother cat starts pushing her kittens away from her when it is time to wean them: but human bottle feeders often don't do this. So the kitten doesn't learn how to tolerate not getting what it wants. 
None of this matters much, Victoria, if you have a good home, have been neutered, and have learned to be gentle with your humans. Yes you are Purr-fect!
Yours
George
PS. Going to your final home at 12 weeks, which is what most pedigree breeders suggest, is OK as long as you have had a proper upbringing with the breeder, met other cats, and met lots of humans. If you were born in a chalet and not handled enough, 12 weeks is late to learn about humans. But it is not impossible - look at Abby's progress here.