This can be answered in a number of ways. We are biological machines so intelligence is a biological property. It’s not spiritual, or driven by clouds. It’s biology that does intelligence. If it’s a human doing it, it has a biological basis.
The question of what we mean by intelligence does have cultural elements. In our culture for example we tend to think of footballers as performing a property of the body, while completing crosswords as being something related to the brain. But actually footballers have amazing brains. They have physical fitness but they also have extraordinary mental abilities that allow them to control their bodies and anticipate the position of the ball and so on.
"What we really mean by intelligence has got nothing to do with what books you’ve read"
A lot of measures of intelligence - what we would call classic intelligence - come down to how you speak, how you dress and your cultural references. If you don’t know who Shakespeare is then in the Western context you’re thought of as being stupid. Well, maybe, but actually intelligence, what we really mean by intelligence has got nothing to do with what books you’ve read.
In terms of inheritability it’s a controversial topic but there’s fairly good evidence that a certain proportion - somewhere between 10% and 90%, so it’s quite variable, but somewhere around half - is driven by your genes.
So what we call intelligence is partly determined by culture. Different cultures have different views on what intelligence means. However, no matter how you define it, how much of it is heritable?
"If you look at the variation of whatever it is that you’re interested in across the population and you ask how much of this variation is explained by genetics, you’ll find that about half of it is."
What you’ll probably find is about 50% of intelligence is heritable. So if you look at the variation of whatever it is that you’re interested in across the population and you ask how much of this variation is explained by genetics, you’ll find that about half of it is, and half of it - admittedly these are very rough numbers - comes from the environment, upbringing and so on.