Of course, my experience with extended family did not include some elements in small-scale tribes. For example, in hunter-gatherer societies, parents and children live together in close proximity. Children see their parents have sex all the time and imitate it in sexual games among themselves. This was treated with no particular alarm by adults.
However, other family characteristics are very familiar: Aunts and uncles share childcare frequently (I played with my cousins and ate at my aunt's house countless times); grandparents take over much of the work; the specific role and boundaries of biological parents are blurry. This stirs up a lot of memories.
When I was in the nuclear family with my parents and brother, I was in fact home alone most of the time. Both parents went to work, and my brother went to school. I often ran off to my cousins house and played there until my parents came home from work. This was the norm until I started school at 6 and a half years. But my memory of being in my grandparent's house is much stronger and more vivid. In their Shanghai house with narrow, steep, creaky wooden stairs, people came and went all day long, most of whom I knew not. My grandfather's father had three wives, resulting in a huge number of relatives with tenuous and ambiguous relationships. They randomly dropped in for a social visit and exchanged gossips and gifts, and then stayed for a meal. It was said that grandmother could never turn anyone out before lunch. I loitered with my cousins and uncles of the same age in the background, playing games of our own. Children were well fed but otherwise ignored. I never got a fraction of the attention in Shanghai as I did at home as the youngest child. Most of the time it was chaotic and confusing and had nothing to do with me. Yet I often recall the sense of peace and safety in my grandparents' house, with constant chatter (in the Ningbo dialect) and the smell of food.
Diamond writes that anthropologists have documented their surprise at how far advanced tribal children are in social maturity, compared with children in Western countries. He attributes this maturity with their contacts with adults of various ages and generations all the time, while Western children have limited contacts with adults other than their parents and are often segregated by age in daycare and school.
I wonder if I would have become a more social person if I had grown up in my grandparents' household.